Refer to: Kerndt PR, Naughton JL, Driscoll CE, et al: Fasting:The history, pathophysiology and complications (Medi-cal Progress). West J Med 1982 Nov; 137:379-399 AMedical Progress

Fasting: The History, Pathophysiology

and ComplicationsPETER R. KERNDT, MD, and JAMES L. NAUGHTON, MD, San Francisco;

CHARLES E. DRISCOLL, MD, and DAVID A. LOXTERKAMP, MD, Iowa City

An appreciation of the physiology of fasting is essential to the understandingof therapeutic dietary interventions and the effect of food deprivation in variousdiseases. The practice of prolonged fasting for political or religious purposes isincreasing, and a physician is likely to encounter such circumstances. Early infasting weight loss is rapid, averaging 0.9 kg per day during the first week andslowing to 0.3 kg per day by the third week; early rapid weight loss is primarilydue to negative sodium balance. Metabolically, early fasting is characterizedby a high rate of gluconeogenesis with amino acids as the primary substrates.As fasting continues, progressive ketosis develops due to the mobilization andoxidation of fatty acids. As ketone levels rise they replace glucose as theprimary energy source in the central nervous system, thereby decreasing theneed for gluconeogenesis and sparing protein catabolism. Several hormonalchanges occur during fasting, including a fall in insulin and T3 levels and a risein glucagon and reverse T3 levels. Most studies of fasting have used obesepersons and results may not always apply to lean persons. Medical complica-tions seen in fasting include gout and urate nephrolithiasis, postural hypoten-sion and cardiac arrhythmias.

WE REVIEW IN THIS PAPER the current understand-ing of the pathophysiology of fasting and starva-tion. Although fasting implies an intentional ab-stention from food, the physiologic adaptivemechanisms (not necessarily psychologic) thatcome into play during this type of food depriva-From the Department of Medicine, University of California,

San Francisco, and the Department of Family Practice, Universityof Iowa College of Medicine, Iowa City.

This project was funded in part by a student assistantship of thepredoctoral training grant in Family Medicine (#5D15 PE98002-O1STC) from the United States Department of Health, Education,and Welfare, Public Health Service, Health Resources Adminis-tration, Bureau of Health Manpower.

Reprint requests to: James L. Naughton, MD, Department ofMedicine, University of California, San Francisco, CA 94143.

tion are similar to starvation. These terms will beused synonymously, therefore, except when im-portant differences are known to exist.An appreciation of the physiology of fasting is

essential for understanding many kinds of thera-peutic dietary manipulations. Critical evaluationof protein-sparing diets, ketogenic diets or otherhypocaloric mixed-diet regimens requires a knowl-edge of the response to acaloric fasting. Becausemany illnesses result in food deprivation, physi-cians should understand the usual physical andmetabolic consequences of starvation; an illustra-

THE WESTERN JOURNAL OF MEDICINE 379

FASTING

tive case that was monitored according to a studyprotocol is presented. The effects of fasting arereviewed in association with the individual effectsobserved in the case.

A study protocol was designed to monitor afasting person and was submitted to and approvedby the Human Experimentation Committee of theUniversity of Iowa College of Medicine, IowaCity, Iowa.

A Brief History of FastingSince early times, fasting has been advocated

for spiritual development and promotion of health.Fasting as a religious practice developed inde-pendently among different people and religionsworldwide.' In ancient Greece the belief that tak-ing food risked entry of demonic forces con-

tributed to the popularity of fasting. Fasting was

required in preparation for many rituals thatsought contact with supernatural forces.2 Greatimportance was placed on fasting as a means ofarousing ecstatic forces, dreams or visions. Py-thagoras, Abaris and Epimenides in ancientGreece extolled the virtues of fasting, and inbiblical times Moses, Elias and John the Baptistrecognized its religious value.' During the holymonth of Ramadan, Moslems abstain from allfood and drink between dawn and dusk.'

In the Old Testament fasting was regarded as

a powerful prayer that could prepare a prophetfor divine revelations (Daniel 10:2-14). AlthoughChrist fasted for 40 days in the desert (Luke 4:1-2; Matthew 4:2-3), he left no definite law on

the subject except to insist that it be done humblyand privately (Matthew 6:16-18). With time,customary observances of fasting developed inlocal Christian churches partly in an effort to re-

place early pagan and Jewish fasting customs.Fasting in the monastic tradition flourished in thefourth and fifth centuries, the dominant motivebeing asceticism guided by a spirit of penance andself-humiliation as a monk sought communionwith his God.- The motive for the case reportedin this paper was consistent with the monastictradition and was a prayerful penitential response

to modern-day social injustice.

Historically, fasting for health has been advo-cated by many.45 In the mid-1800's, B. H. Dewey,MD, in his book Thle True Science of Living,wrote, "every disease that afflicts mankind [de-velops from] more or less habitual eating in excessof the supply of gastric juices." His "miraculouslycured" patient and later publisher, Charles Has-kell, did much to promote the fasting cure.4 UptonSinclair, better known for other literary works,wrote extensively on the health benefits of fasting.5

Notable nonobese persons who engaged in pro-longed fasting and whose experiences were re-corded in the early medical literature includeTanner who reportedly fasted for 40 days in1880(.67 Alexander Jacques, a Frenchman, fastedfor 30 days in 1887 and for 40 and again 30 daysin 1888.7 Signor Succi, an Italian professionalfaster, claimed to have completed at least 32 fastsof 20 days or more8; his longest recorded fastswere 40 and 45 days in 1890.9 In 1905 a phy-sician, F. Penny, MD, prompted by the claims ofDewey, fasted for 30 days and recorded simpleobservations on himself.10 Observations duringfasts in nonobese persons are less extensively re-corded in the modern medical literature. Bene-dict's classic study in 1912 of Mr. L, who fastedfor 31 days, included detailed physical and meta-bolic measurements.9 In 1946 Bernard cameunder medical observations on the 40th day of apurported 45-day fast.11 About the same time,Gamble's classic life-raft studies, wherein volun-teers were subjected to food and water deprivationunder conditions simulating being lost at sea, didmuch to elucidate the essential water require-ments and protein-sparing effect of carbohydrate.12In the early 1950's Ancel Keys and co-workers"1at the University of Minnesota compiled extensivedata on 32 volunteers who underwent eightmonths of semistarvation.

Fasting as a therapy for obesity has long beenadvocated. Folin and Denis in 191514 recom-mended repeated short periods of starvation as asafe and effective method of weight reduction. Inmodern times Bloom," Duncan and associates'6and Drenick and colleagues'7 advocated prolongedfasts for weight reduction in morbid obesity.Drenick and colleagues'7 placed obese persons onfasting regimens of up to 117 days, whereasThomson and co-workers'8 monitored fasts of139, 236 and 249 days. The longest recorded fastwas that of a 27-year-old obese man who fasted382 days and lost 125 kg (276 lb).'9 Since thelate 1950's many of the data on the metabolism of

380 NOVEMBER 1982 * 137 * 5

ABBREVIATIONS USED IN TEXT

FSH= follicle-stimulating hormoneT3= triiodothyronineT4= thyroxineTSH= thyroid-stimulating hormone

FASTING

fasting come from studies carried out on obesepersons willing to fast for weight reduction.

Fasting for the treatment of convulsive disor-ders was used in France by Guelpa and Marie in1910 (as cited by Keith20) and later investigatedhere by Geyelin in 1921.21 Changes in the acid-base balance were originally thought to be re-sponsible for the anticonvulsant effect until Wilderin 1921 (also cited by Keith20) suggested a rolefor starvation-induced ketone bodies. Since thattime, ketogenic diets have been used successfullyin the management of seizure disorders refractoryto conventional drug regimens.22

Fasting has often been used as a means ofpolitical protest. Gandhi fasted for political rea-sons on at least 14 occasions, 3 times for as longas 21 days.23 One of the longest recorded politicalfasts in a nonobese person was by Terence Mac-Swiney, a former mayor of Cork, who fasted for74 days to his death after his arrest during Eng-lish-Irish unrest in 1920.24 Joseph Murphy, lesswell known but also a member of the Irish Volun-teers, died on the same day as MacSwiney after76 days of a hunger strike.24 The hunger strike asa means of political persuasion is being used stillin Ireland: To date ten members of the Irish Re-publican Army have fasted from 45 to 61 daysto their death in the now-infamous H block of theMaze prison in Belfast, Northern Ireland.25

Study ProtocolA complete physical examination, including an

electrocardiogram and a roentgenogram of thechest, was carried out before the fast. Laboratorydeterminations that were also done includedserum potassium, chloride, calcium, phosphorus,uric acid, creatinine, total protein, albumin, glob-ulin, triglycerides, total lipids, total bilirubin, directbilirubin, aspartate aminotransferase (glutamic-oxaloacetic transaminase), alanine aminotrans-ferase (glutamic-pyruvic transaminase), alkalinephosphatase, lactic dehydrogenase, thyroxine, iron,blood urea nitrogen, glucose and a complete bloodcount, including a differential cell count, usingstandard methods at METPATH, Teterboro, NewJersey.* Insulin, glucagon, growth hormone andplasma amino acid levels were measured usingmethods reported elsewhere.26-29 Follicle-stimulat-ing hormone and luteinizing hormone levels weremeasured using standard radioimmunoassay tech-

*Drs. L. J. Filer, L. D. Stegink, R. Thompson and D. E. VanOrden at the University of Iowa made available the use of theirlaboratory facilities and personnel for preparing many of the de-terminations for this study.

niques. Zinc concentration was measured using aPerkin-Elmer atomic spectrometer. A urine speci-men was collected for measurement of totalvolume and pH, qualitative determination of ke-tones, protein, blood, bilirubin and glucose, andquantitative determinations using standard meth-ods for sodium, potassium, chloride, calcium,phosphorus, magnesium, urea, ammonia, creati-nine, uric acid and total nitrogen.

Fluid intake (water only) was initially two litersa day for the first three weeks, then decreasedto and maintained at a liter per day during thefinal week of the fast. A total intake of 60 caloriesfrom daily communion was recorded during thefast. The subject was ambulatory throughout thefasting period and was weighed daily on arisingand after voiding. Pulse rate and blood pressurewere determined twice a day. Electrocardiogramswere obtained weekly. Complete physical exami-nations were done weekly for the first three weeks,followed by daily physician visits (provided byJames Pearson, MD, Dubuque, Iowa) in the lastten days of the fast. Medical consultation wasavailable by telephone at any time or by a phy-sician visit within 20 minutes. All laboratory testswere repeated weekly except a dipstick urine anal-ysis, which was done daily.

Case Report and Review of the Literature

A 41-year-old nonobese man, a member of acloistered religious community, chose to undergoa 40-day acaloric fast. He requested that his fastbe supervised medically to minimize any risk tohis health. Monitoring was to be carried outwithin the confines of the monastic enclosure with-out undue distraction from the intent of the fastwhile maintaining strict anonymity for himselfand his religious community. After all risks in-cluding the possibility of sudden death were dis-cussed, a form releasing us from legal liabilitywas signed. Furthermore, it was agreed that thefast could be terminated at any time either by himor upon medical recommendation. The past medi-cal history was significant for occasional benignventricular premature contractions and iron de-ficiency anemia. His usual diet had been ovolac-tovegetarian (that is, vegetables, eggs and milkproducts) for the preceding 24 years.

Control Data

On physical examination before commencementof the fast the man weighed 68.6 kg, was 172 cmtall and appeared in no acute distress. His skin

THE WESTERN JOURNAL OF MEDICINE 381

FASTING

TABLE 1.-Mean Blood Pressure and Pulse Changes in the Upright and Supine Positions atWeekly Intervals in the Fasting and Realimentation Periods

Suipine UprightDay of Mean Blood Pressure Mean Puilse Rate Mean Blood Pressure Mean Pulse RateStuidy (torr) (beats/nuin) (torr) (beats/min)

Fastinig Period1-7 .... 110/66 (128-96)/(82-58)* 55 (60-48) 107/75 (124-92)/(92-64) 73 ( 90-64)8-14 .. 108/64 (112-98)/(76-58) 54 (60-50) 90/65 ( 96-86)/(72-58) 88 (106-70)

15-21 .. 104/62 (110-98) / (66-60) 55 (60-50) 80/54 ( 92-72) / (58-46) 82 ( 96-68)22-28 . .. 100/61 (114-92)/(72-52) 57 (60-54) 72/54 ( 84-64)/(62-50) 86 ( 90-78)29-36t .. . 92/53 ( 98-88)/(60-46) 56 (58-54) 70/51 ( 76-64)/(58-46) 83 ( 92-78)

Postfast Period1-7 .... 100/59 (112-88)//(80-60) 60 (66-56) 70/53 ( 78-62)/(62-42) 96 (112-80)

*Range included in parentheses.tMean calculated on the basis of an 8-day period.

was clear and the head, eyes, ears, nose and throatshowed no abnormalities. Examination of thechest showed a mild pectus excavatum and thelungs were clear to auscultation and percussion.OIn cardiac examination there were normally splitfirst and second heart sounds with a grade 2/6systolic ejection murmur present along the leftsternal border without radiation or change withthe Valsalva maneuver or position. The abdomenwas soft, nontender and without evidence of hep-atosplenomegaly. Prostatic enlargement was notedon examination of the rectum. Guaiac test of astool specimen was negative for occult blood. Noclubbing, cyanosis or edema was present in theextremities. Peripheral pulses were normal. Therewas no lymphadenopathy. On neurologic exami-nation there were no aibnormalities found.An electrocardiograim showed sinus bradycar-

dia with a rate of 45 to 50 beats per minute andan incomplete right bundle branch block. A tread-mill exercise stress test done 1 6 months earliershowed no abnormalities at 100 percent of maxi-mal predicted heart rate. An x-ray film of thechest showed only the small pectus excavatumdeformity.

Physical Adaptations to FastingThe subject fasted for 36 days until profound

weakness and symptoms of postural hypotensioninterfered with his daily activities in the monastery.

Weight LossHe lost 15.7 kg or 22.9 percent of his initial

body weight after 36 days of acaloric fasting.Weight loss continued through the first two daysof realimentation, resulting in a total weight lossof 16.6 kg or 24.2 percent of initial body weight.The rate of weight loss was initially 0.9 kg per

WEIGHTKG70 r

5 1 0 1 5 20 25 30 35DAY OF FAST

Figure 1.-Rate of weight loss during total fasting inour subject and Mr. L, studied by Benedict in 1912.9

day for the first five days, then it gradually de-creased over the next two weeks and becamestable at 0.3 kg per day after the third week.The total weight loss and the rate of loss com-

pare favorably with those reported elsewhere: Inthe initial fasting period (one to five days), weightloss occurs at the rate of 1 to 2 kg per day fol-lowed by a gradual decline through the thirdweek, thereafter averaging 0.3 kg per day.30 InBenedict's study," Mr. L lost 13.25 kg or 21.9percent of initial body weight after 31 days offasting. This compares with a 14.2-kg loss or 20.7percent of initial body weight after the same timein our subject (Figure 1).

Pulse RateOur subject's pulse rate did not decrease sig-

nificantly during fasting (Table 1). This mayreflect the presence of bradycardia in this well-conditioned man before onset of fasting. Slowingof pulse rate during prolonged periods of de-

382 NOVEMBER 1982 * 137 * 5

FASTING

creased caloric intake is otherwise well docu-mented.913'313 2 Benedict9 reported that the pulserate reached a minimum during the second tothird week of total fasting and then increased inthe fourth week. In another study13 of 32 volun-teers on semistarvation diets for 32 weeks whohad an average weight loss of 16 percent, the pulserates steadily declined, reaching a mean of 35.3beats per minute at 13 weeks; however, after anadditional ten weeks of caloric restriction andanother 10 percent reduction in body weight, thepulse rates rose slightly but significantly to a meanof 37.3 beats per minute. In the studies by Jewishphysicians during the siege of the Warsaw ghettoin World War II, bradycardia was seen in adultsand children in all stages of starvation.33

Blood PressureIn our study the mean blood pressure calculated

for weekly intervals fell from 110/66 mm ofmercury during the first week to 92/53 mm ofmercury during the last eight days of the fastingperiod (Table 1). Blood pressure increased sig-nificantly toward prefast values in the realimenta-tion period. Pronounced orthostatic hypotensionoccurred by the second week and persistedthroughout the fasting period. The subject becamesymptomatic after several days and was nearlyincapacitated by the postural hypotension after33 days, requiring 20 to 30 minutes to go fromthe supine to the upright position on rising in themorning. Subjectively, the postural symptoms im-proved as the day progressed. There were nosyncopal episodes during the fasting or realimen-tation periods.A fall in blood pressure is a consistent

observation during fasting and semistarvationstates.'9"l3s4 The development of symptomaticorthostatic hypotension during fasting is not pre-dictable but seems to depend on the individualperson, the duration and the type of fast. Drenickand colleagues17 noted incapacitating posturalhypotension in 3 of 11 obese persons after 25, 60and 62 days of fasting. More recently, sevenobese patients placed on a regimen of 400 kcal ofprotein per day and later 400 kcal of a mixeddiet (50 percent protein, 50 percent carbohydrate)per day were followed for periods of 3 to 5½/2weeks. 5 While on the protein diet, the systolicblood pressure fell 28±3 mm of mercury versus18±3 mm of mercury on the mixed diet. Symp-toms of orthostatic hypotension developed in allpatients while on the protein diet and in only one

while on the mixed diet. Along with raised serumketone levels and increased salt excretion, plasmalevels of norepinephrine were reduced in thebasal state and after two minutes of standing inpersons receiving the pure protein diet but notwith the mixed diet regimen. The mechanism ofthe different effects of pure protein versus mixeddiets on the sympathetic nervous system is notyet fully understood.

In another study using animals, an associationbetween fasting and overfeeding with sucrose andrates of norepinephrine turnover was found."6 Asignificant reduction in norepinephrine turnoverwas seen in food-deprived rats versus an increasedturnover in rats overfed with sucrose. Should asimilar mechanism exist in man, an essential rolefor dietary carbohydrate in the maintenance ofsympathetic nervous system function could bepostulated.

ElectrocardiogramsOn our subject's electrocardiograms, shifts to

the right of the QRS (30 degrees to 60 degrees)and to a lesser extent T-wave axis (50 degrees to60 degrees) occurred. A decrease in amplitudefrom 6 to 3 mm was seen in the QRS complexonly in lead I.

Changes in the electrocardiogram during fast-ing and semistarvation are well known.""13 19 738

Changes most frequently reported include sinusbradycardia, decreased QRS complex and T-waveamplitude, and shifts to the right of the QRS andT-wave axes. In the Minnesota semistarvationstudy,"1 a decrease in the amplitude of all deflec-tions (P wave, QRS complex and T wave) oc-curred with a shift to the right of the QRS andT-wave axes; though the QT interval and dura-tion of mechanical systole increased, the PR andQRS intervals and the duration of the P wave didnot change. In case reports of World War IIprisoners suffering from severe malnutrition, re-versible electrocardiographic abnormalities includ-ing pronounced prolongation of the QT interval,to a lesser extent lengthening of the PR and QRSintervals, depression of the ST segment andchanges in the T wave were noted. Similarly,prolongation of the QT interval and abnormal STsegment and T wave are consistent findings inpatients with anorexia nervosa.39

The mechanism underlying these electrocardio-graphic changes is unknown. Atrophy of cardiacmuscle has been observed in starvation.'7"8 and

THE WESTERN JOURNAL OF MEDICINE 383

FASTING

many of these electrocardiographic changes mayreflect decreased cardiac mass.

Natriuresis

The early high rate of weight loss in our sub-ject cannot be explained on the basis of energyexpenditure alone. If the initial 0.9 kg per dayweight loss observed were to reflect loss of bodyfat, carbohydrate and protein, it would require anenergy expenditure of 3,150 calories per day. Thisis far in excess of the basal energy expenditure40of 1,673 calories per day predicted for this manin the early fasting period. It is now well estab-lished that early accelerated weight loss duringfasting is the result of salt and water diuresis.41-43

Because no attempt was made to equilibratesalt intake in the prefast period in our study,urinary sodium levels (as well as other electrolyteand mineral determinations) on day 1 reflect theprevious unmeasured dietary intake. However,cumulative sodium loss was estimated at 325mEq over the first seven days and the peak neturinary sodium loss was 68 mEq in one day andoccurred on day 3. The sodium loss correspondedto an 0.9 kg per day weight loss and 0.9 liternegative fluid balance (insensible losses not in-cluded). Urinary chloride loss followed a similarpattern but was quantitatively less than sodiumloss. Cumulative urinary sodium losses in the firstweek of fasting in our subject were comparableto those observed by others (200 to 350 mEq),but the peak sodium loss of 73 mEq on day 3was somewhat less than the 100 to 150 mEq peaklosses reported elsewhere to occur on fasting days3 or 4.30Numerous explanations have been offered for

the early natriuresis during fasting includingchanges in renal tubule sodium-transport systems,glomerular filtration rate, aldosterone secretion,ketoacidosis or an osmotically induced diuresis.30All fail to explain this phenomenon entirely. Itnow appears that this natriuresis is, in large part,the result of obligatory sodium loss due to thegeneration and high early excretion of ketonebodies.42'43 As liver glycogen stores are depletedand body energy requirements are met by mobili-zation of fat stores, serum and urinary levels ofmetabolically generated anions in the form ofketones increase. Excretion of these anions re-quires an accompanying cation that initially issodium. Ammonium production increases underthe stimulus of metabolic acidosis (ketoacidosis)and ammonium replaces sodium as the major

rTp. E q(24)4 ; i t_' l!L S40 '

2'<C

100

80

60 --

40 l

20

O. NHl3 mEq:24 hrs

I Na+ m.EQ/24 ho-

rl

3

_2r 30 P5

Figure 2.-Urinary sodium (Na+) and ammonia (NH3)losses during the fasting period.

urinary cation. During the period when urinaryexcretion of ammonium is lagging behind ketoneexcretion, peak rates of sodium excretion are ob-served (and maximum weight loss occurs). 42-44This pattern was seen in our subject: urinaryammonia excretion increased through day 9 assodium excretion gradually declined (Figure 2).Hormonal mechanisms have also been impli-

cated in the natriuresis of early fasting. Glucagonlevels rise during this period; experimentally, in-fusions of physiologic doses of glucagon in non-fasting subjects induce a similar natriuresis45 whileadministration of insulin can cause renal sodiumretention.46 Therefore, the rising glucagon andthe falling insulin levels during the early phase offasting may both contribute to sodium excretion.

Carbohydrate refeeding after fasting (thoughthe diet may still be hypocaloric) produces anabrupt weight gain with an immediate reversal ofurinary salt and water loss.12'47-49 At times thesodium retention is profound, resulting in frankedema formation. Isocaloric refeeding with fatdoes not result in sodium retention whereas re-feeding with protein produces a delayed but sig-nificant antinatriuresis.48 The mechanism of so-dium retention with carbohydrate realimentationis not well understood. Rising insulin and fallingglucagon levels may be involved but are unlikelyto account for frank edema formation. The aldo-sterone level is not consistently raised and usuallyfalls with realimentation.50 A reversal of this pat-tern of urinary excretion of solutes, namely per-sistent secretion of ammonium after suppression

384 NOVEMBER 1982 * 137 * 5

F- .-' -iT

r5 51 :..,

FASTING

of ketonuria by carbohydrate realimentation,could also contribute to sodium retention.

Metabolic Adaptation of FastingFuel StoresThe composition of total body fuel stores in

humans is well understood (Table 2). In fastingstates liver glycogen is depleted in the first 18 to24 hours.30 Protein, which has essential enzyma-tic, structural and mechanical functions, consti-tutes 15 percent of total body energy stores.5'Because of these essential functions, the break-down of a third to a half of the body protein storesis believed incompatible with life.'2 Muscle, an-other site of glycogen stores, lacks glucose-6-phosphatase and therefore cannot release glucosedirectly into the bloodstream.53 Fat in the form oftriglycerides in adipose tissue provides the largestand most efficient storage of body energy and con-stitutes 85 percent of all potentially availablecalories.' In a 70-kg person basal caloric require-ments could be met solely from fat stores for twoto three months in the absence of any caloricintake.51"53"54

Glucose HomeostasisIn our subject blood glucose levels fell early

during fasting and remained low throughout thefasting period. Insulin levels became appropri-

TABLE 2.-Body Fuel Stores of Healthy Humans*

Percent ofBody Fuel Source Kg Calories Total Fuel

Fat (adipose) .......... 15.0Protein (mainly muscle) 6.0Glycogen (muscle) ..... 0.150Glycogen (liver) ....... 0.075

*Modified from Cahill et al.51

141,00024,000

600300

85.0014.500.350.15

ately reduced as glucagon increased significantly(Table 3).The transition from the fed state through brief

fasting and into prolonged starvation is mediatedby a series of complex metabolic, hormonal andglucoregulatory mechanisms. The interrelation-ship between body fuel stores and the time se-quence for their mobilization via glycogenolysis,gluconeogenesis, lipolysis and ketogenesis is dia-gramed in Figure 3. Felig30 conveniently dividedthe transition from a fed to a fasted state intothree stages: (1) the postabsorptive phase, 6 to24 hours after beginning fasting, during whichcerebral glucose requirements are maintained pri-marily via glycogenolysis, (2) the gluconeogenicphase, from two to ten days of fasting, duringwhich glucose requirements are met using gluco-neogenic amino acids, lactate, pyruvate and glyc-erol, and (3) the protein conservation phasebeyond ten days of fasting, characterized by de-creasing protein catabolism as fat stores aremobilized and tissue use of free fatty acids andketones increases.

In the postabsorptive state, total glucose use is

RATE

LIPOLYSIS/KETOGENESIS

GLUCONEOGENESIS

- GLYCOGENOLYSIS

1 3 10 20DAY OF FAST

Figure 3.-A schematic of the changes in rates ofglycogenolysis, gluconeogenesis, lipolysis and keto-genesis that are required to maintain caloric homeo-stasis during the transition from brief to prolongedfasting.

TABLE 3.-Serum Glucose, Insulin, Glucagon, Growth Hormone, Total Lipids andTriglyceride Levels in Our Subject Before, During and After Fasting

Growth Total Triglyc-Day of Glutcose Instulin Glucagon Hormone Lipids eridesStuidy (ntg/dl) (,ulU/ml) (pg/ml) (ng/ml) (mg/dl) (mg/dl)

Prefast Period

Fastinzg Period5 ......

12 ......19 ......26 ......33 ......36 ......

96 13.5

637471777656

Postfast Period7 ...... 13512 ...... 90

2.915.312.641.501.342.55

16.0

THE WESTERN JOURNAL OF MEDICINE 385

138.7

222.1161.8248.5327.8727.8198.2

218.9

0.73

2.924.107.959.863.124.51

0.82. .

530

430440410400470400

500470

72

118122136101111124

314125

FASTING

LIVER BLOOD MUSC

/GLUCOQSG

P YR U VAPYRUIVATE Ui

ALAN IN E

Figure 4.-The glucose-alanine cycle. Gleased by the liver is taken up by muscleconverted to pyruvate and transaminated t4nine. The alanine thus synthesized is rmuscle and taken up by the liver whereskeleton is reconverted to glucose, thus corrcycle (from Felig55).

150 to 250 grams per day.,5 The brainthe largest fraction, about 125 to 1'while resting muscle cells and obligatecells in bone marrow, blood, peripheralrenal medulla consume the remainder.glycogenolysis provides about 75 perctglucose requirements early in fastingglycogen reserve of 70 grams. Thecomes from gluconeogenic precursoracids (10 percent to 15 percent), lapyruvate (10 percent to 15 percent) an(.1 percent to 2 percent). Muscle gimetabolized to lactate that is releaseccirculation and is resynthesized into gthe liver and kidney. Although this prnCori cycle) results in no net production (

an advantage exists in that glucose syntlprotein catabolism is reduced and the (

resynthesis is derived from the oxidati(fatty acids, a plentiful and readily availasource.,' Glycerol, a by-product of theof triglycerides and release of free faprovides a small but significant nonrrived gluconeogenic precursor in proloing."5 Thus, although humans cannotglucose directly from fat, the energy deioxidation of free fatty acids facilitatesynthesis from lactate and glycerol.As mentioned earlier, gluconeogen

protein-derived amino acids provides 1

'LE to 15 percent of the substrate in the early fastingperiod. Although all amino acids except leucineare potentially gluconeogenic, a specific patternof precursor availability occurs. Alanine, whichconstitutes no more than 7 percent to 10 percent

- of all amino acid residues in skeletal muscle,accounts for 30 percent to 40 percent of aminoacids released from muscle after an overnightfast.55 It is now well established that this increasedoutput represents de novo alanine synthesis in

NH2 muscle by transamination of pyruvate.55Felig and associates57 noted that the concentra-

AMING ACIDS tions of branched chain amino acids (valine, leu-cine, isoleucine) are increased early in fasting,reaching a peak at approximately the fifth day.These amino acid and serum alanine levels rose

ilucose re- early during the fasting period in our subject. Thewhere it is branched chain amino acids appear to be pref-eleased by erentially catabolized in muscle and provide theits carbon nitrogen source for the transamination of pyruvatenpleting the to alanine.'8 Subsequently, the alanine released by

muscle is taken up by the liver and kidney whereit is resynthesized into glucose.57 The aminoconsumes

50 grams groups are converted to urea, which is excreted inanaerobic the urine. This glucose-alanine cycle, which isanaerobv c comparable to the Cori cycle discussed earlier,nerve and represents a major glucohomeostatic mechanism

ent of the in the early fasting period (Figure 4). This cyclefntrof ith provides a source of alanine that the liver uses,

remainder more efficiently than it uses any other amino acid,-s: amino to make glucose.57 It also establishes several con-ictate and trol points for feedback inhibition of gluconeo-

cd gla al genesis-that is, insulin reduces gluconeogenesisby inhibiting hepatic alanine uptake,57 and ketosis

lycogen is inhibits gluconeogenesis'9 by decreasing the deg-I into the radation of branched chain amino acids that inlucose by turn removes the source of nitrogen for alanineocess (the synthesis.of glucose, As fasting progresses, plasma glucose levels fallenesis from significantly whereas the level of glucagon rises.n0energy for The fall in plasma glucose level is greater in fe-on of free male than in male subjects.61 Merimee andble energy Tyson" noted a mean plasma level of glucose ofhtydrolyids 47.8 ±2.9 mg per dl in 12 nonobese women who)rteacinde- fasted for 72 hours compared with 66.4±2.9 mg)rotein-de- per dl in 12 nonobese men who also fasted for 72nged fast- hours. The reason for this sex difference is notsynthesize clear. Relative muscle compartment size'62 (womenrived from have a lower lean body mass-to-adipose ratio)-s glucose and estrogen and progesterone modulation of tis-

sue uptake';i and use of glucose have been sug-esis from gested as possible explanations. Women are alsoI0 percent known to become ketotic more rapidly than men

386 NOVEMBER 1982 * 137 * 5

FASTING

during fasting, and ketosis appears to decreasegluconeogenesis, thereby indirectly affecting plas-ma glucose levels.

Protein ConversionNitrogen Balance

In our subject, total urinary excretion of nitro-gen fell from 10 to 12 grams per day in the firstweek to 5 to 7 grams per day after the third week(Figure 5). In prolonged starvation survival de-pends on conserving protein stores while energyfor essential metabolic functions is maintained.Evidence that protein catabolism is reduced withcontinued fasting is reflected by the decrease intotal uriniary excretion of nitrogen. As expected,the urinary nitrogen excretion in our subject wassomewhat greater than the losses of 3 to 6 gramsper day observed in fasting obese persons.64 Cere-bral adaptation to ketone use lowers glucose re-quirements, thereby reducing the need for glu-coneogenesis.65 The fall in urea excretion (Figure5) suggests decreased hepatic gluconeogenesisfrom amino acids.64 In addition, the hyperketone-mia of starvation may exert a direct inhibitoryeffect on gluconeogenesis. Sherwin and co-work-ers59 found a reduction in serum alanine levels of30 percent after one-hour infusions of p-hydroxy-butyrate in obese persons who fasted for five toten weeks (Figure 6).

Along with this fall in blood alanine level, totalurinary nitrogen excretion decreased 30 percent.As discussed previously, alanine is the majoramino acid gluconeogenic precursor during fast-ing. A reduction in alanine formation results indecreased gluconeogenesis and hence a decreasein protein catabolism. Thus it would appear thatthe hyperketonemia of starvation exerts a directprotein-sparing effect by reducing alanine releasefrom muscle. Although the exact mechanism isnot known, it has been suggested that ketones maydirectly inhibit the oxidation of branched chainamino acids in muscle, thereby stopping the syn-thesis of alanine and turning off the glucose-ala-nine cycle.59

Conversely, recent evidence indicates that ala-nine may inhibit ketone production directly, sug-gesting the presence of a ketone-alanine cycle.66The importance of substrate cycling in homeo-static control of intermediary metabolism has onlyrecently been appreciated, and in the case of aketone-alanine cycle further investigation to eluci-date its full significance is required.

Also apparent in Figure 5 are the changes in

urinary ammonia levels. Ammonia productionand excretion increase steadily (maximal by day10) under the stimulus of ketoacidosis.64 As dis-cussed earlier, the major obligate cation lost earlyin fasting (to compensate for the increased excre-tion of metabolically generated anions) is sodium.As fasting progresses, sodium conservation is

UREA* .-- AMMONIA

.*:-- , iURIC ACID- ::CREATiNE

E _8~~~~~~~~~~~~~~~~~~~~~~~~~-

r2AY OF TAS'K

Figure 5. Total urinary nitrogen excretion. Note thegradual increase and then decrease of urinary excre-tion of ammonia and the absolute reduction in totalnitrogen excretion as fasting progresses.

PRE S POST'NFUSION OHSB INFUSION

I: r-..!1 .

: ,I -, 1

i 3i

i 11I tI

Id JAM.MONIA TOtAL

|[3 fTROGEN N;TROGF

._ A wo .

Figure 6.-The effect of an infusion of /8-hydroxybuty-rate (,B-OHB) on urinary nitrogen excretion and plasmaalanine concentration during prolonged (five to tenweeks) fasting. Infusions were for 12 hours (9 AM to 9PM) on each of two consecutive days, and data present-ed are mean values for five subjects. Plasma alanine andurinary nitrogen levels fell significantly (P<.025) inresponse to the infusion (from Sherwin et al59).

THE WESTERN JOURNAL OF MEDICINE 387

--I -; - 4,. %..'%L

-.v. .

1.A.

i

FASTING

NETURINARYEXCRETION

5 KET O N E~~~~~~~~~~ETNS

3 10 15 20

DAY OF FAST

Figure 7.-A schematic of the relationship betweenketonuria, ammoniuria and the natriuresis of fasting.Sodium (Na) losses decrease as ammonium (NH4) be-comes available as a cation to be excreted with ke-tones. Ketone losses decrease due to increased renalreabsorption; this is accompanied by a decreased am-monium excretion.

linked to increased ammonia production and ex-cretion.21'3 The relationship between ketonuria,ammoniuria and the natriuresis of fasting is dia-gramed in Figure 7.

Lipolysis and KetogenesisIn our subject total lipid levels fell slightly

whereas triglyceride levels rose (Table 3). Also,a pronounced increase in triglycerides was seenon refeeding as fuel stores were rapidly replen-ished in the hypercaloric state.

In the transition from a fed to a fasted state,fat stores are rapidly mobilized. Lipolysis, whichis the hydrolysis of triglycerides to free fatty acidsand glycerol, is stimulated by a fall in insulinlevels and a rise in glucagon levels. In the post-absorptive state free fatty acids are mobilized atthe rate of about 7 grams per hour and are takenup by the liver at about 3 grams per hour wherethey are terminally oxidized to CO, (3-oxidation),partially oxidized to ketone bodies (ketogenesis)or resynthesized into triglycerides (lipogenesis) . 0

The major ketone bodies are /-hydroxybutyrateand acetoacetate, which may rise 70-fold duringprolonged fasting.'" Regulation of ketogenesis isdependent on substrate availability (that is, freefatty acids) and transport into the hepatic or renalmitochondria where oxidation occurs. The enzymeresponsible for this transfer, carnitine acyltrans-ferase, is indirectly stimulated by glucagon in theabsence of insulin." As fasting continues, in-creased cerebral use of ketone bodies occurs asgreater ketonemia develops. 7; Serum levels ofketone bodies rise steadily during three to fourweeks,8 whereas lipolysis and ketogenesis aremaximal by three days.';" This discrepancy be-tween increasing serum levels and stable produc-

tion rates is explained by the decreased peripheraluptake and decreased renal excretion of ketones.08Muscle uptake of ketones falls by 75 percent fromearly to prolonged fasting as energy for musclemetabolism shifts from ketones to free fattyacids. In addition to increasing plasma ketonelevels, the increased reabsorption of ketones bythe kidney has a nitrogen-sparing effect by de-creasing the ammonia excretion required to titrateurinary ketone losses.68 Thus, in addition to pro-viding substrate, the ketonemia of starvation pro-vides feedback inhibition of protein catabolism.

Sex Differences and Body Size in theDevelopment of Fasting KetosisAs early as 1931 differences during fasting be-

tween men and women have been shown.7' It wasnot until the late 1950's, however, after Bloom15reintroduced fasting as a treatment of morbidobesity, that interest in and study of fasting me-tabolism became widespread. Rapid weight lossunder medical supervision became a major in-centive for prospective volunteers; as a result,most of the information collected during prolongedfasts during the past two decades is from studieswith obese persons. Unfortunately, in these studiesand in fasting studies with nonobese persons, thedata generally were not analyzed for possible dif-ferences based on sex or body size. Not until 1974was it recognized that there are differences inplasma glucose levels between fasting nonobesemen and women,'G and apparently the influenceof sex and body size must be considered beforeinterpreting any findings.

Deuel and Gulick-' first reported that fastingketosis develops more rapidly in women than inmen. Also, serum free fatty acids and ketonelevels increase at a greater rate in women than inmen during fasting. .27' This sex difference, how-ever, disappears with increasing body weight.74,75Maximal mobilization of free fatty acids occursonly at reduced levels of insulin. However, inobese persons both basal and fasting levels ofinsulin are raised.4 Although insulin is known tobe less sensitive in obese persons,76 at least forits primary action, its secondary or antilipolyticeffect could be a predominant factor in the re-duced rate of lipolysis. In addition, little or norise in growth hormone is seen after prolongedfasting in obese subjects7-79; this hyperinsulinemiaand lower growth hormone level would be ex-pected to make fat mobilization more difficult inan obese person. Conversely, growth hormone

388 NOVEMBER 1982 * 137 * 5

FASTING

levels in nonobese persons are raised during fast-ing,79'80 and in the presence of lower insulin andhigher glucagon levels lipolysis is enhanced. Onemight postulate that in a nonobese fasting personthe stimulus for mobilization of free fatty acidsand ketogenesis is greater due to lower plasmaglucose, lower insulin, and elevated glucagon andgrowth hormone secretion.

Other sex differences include the glucagon level,which has been shown to be higher in nonobesefasting women than in men.81 A role for glucagonin the explanation of the sex-based variation infasting ketosis has been suggested.81 As discussedearlier, ketosis has been shown to decrease therelease of amino acid gluconeogenic precursors(especially alanine) from muscle and may repre-sent another important control point in the regu-lation of intermediary substrate cycling. Merimeeand associates81 found lower but not statisticallysignificant reductions in serum alanine levels be-tween nonobese men and women after 24 and 48hours. Their subjects, however, were chosen basedon previous studies showing similar fasting insulinlevels. They suggested that if women with lowerfasting plasma glucose levels (and hence lowerinsulin production) are studied, a difference in therelease of amino acid gluconeogenic precursorsmight be evident. Furthermore, if a decreased re-lease of gluconeogenic precursors in fasting womenis found, a lower plasma glucose level could beexplained. Further investigation is necessary toresolve this issue.

Other explanations for the greater ketosis infasting women include sex differences in bodycomposition,62 estrogen effects,63 and differentialuse or conversion of free fatty acids to ketones.62The mobilization of fuel stores during fasting de-pends on the energy requirements and the hor-monal milieu. Previous explanations may haveoversimplified the role of certain hormones. Apartial list of differences between men and womenand lean and obese persons is shown in Table 4.

Hormonal ChangesThe important roles of insulin and glucagon in

the adaptation to fasting have already been dis-cussed and have been reviewed extensively byothers.30 Other endocrine changes that also occurduring fasting are as follows.

Growth HormoneWe observed a progressive rise in growth hor-

mone level through day 26 followed by a signifi-cant fall thereafter with a return to baseline levelsduring realimentation (Table 3). Growth hor-mone plays a key role in protein, carbohydrateand fat metabolism. It also has known lipolyticeffects87 and may be diabetogenic in large dosesor in smaller amounts in the absence of insulin.88Its secretion fluctuates widely during the day witha major increase during early sleep.88 Otherknown stimuli to growth hormone secretion be-sides fasting include hypoglycemia, exercise, cer-tain amino acids (for example, arginine and other

TABLE 4.-Differences in Metabolism During Fasting Related to Sex and Body Size*

Obese Subjects Nonobese SubjectsWomen Men Women Men References

SubstrateGlucose ...............................Free fatty acids .14...................... T1Ketones .............................. TTAmino acids (especially alanine) ...... ..... Ot

HormonesInsulin .................................

Glucagon ..................14:tGrowth hormone ..................1MiscellaneousRate of weight loss ..............4.--....Total urinary nitrogen excretion ............Total urinary mineral excretion (calcium,magnesium, phosphorus, sodium, potassium) T

O=no change? = unknown

14I1'01t

14III

14

I

l,1 4 61,62,64,81T T 62,72,73,75,78,81T T 62,71-75,78,81?9 ? 81

I l 61,62,64t T 55,62,810 0 78-80,82

4 14 83-854 4 72,83,85

T1 TT 73,86

*Arrows indicate a relative quantitative change. This table represents a summary of data in an area that has not been adequately studied.'Although no change was noted by Merimee et al,"1 it has been shown that infusions of /8-hydroxybutyrate stimulating the hyperketonemia

of fasting results in a decrease in amino acid gluconeogenic precursors, especially alanine59; on that basis some sex difference might beexpected. Additional studies are necessary.

$Basal growth hormone levels (after an overnight fast) are raised in women compared with men, but no significant increase occurred inwomen after 72 hours of fasting.80

THE WESTERN JOURNAL OF MEDICINE 389

FASTING

TABLE 5.-Serum Thyroxine (T4), Luteinizing Hormone(LH) and Follicle-Stimulating Hormone (FSH) Before,

During and After Fasting

Day of T4 LH FSHStuidy (gg/dl) (mInU/lini) (milIU/11tl)

Before Fastinzg5.9 47 6

Fasting5 ........... 6.5 20 6

12 ........... 6.4 16 419 ........... 5.5 12 326 ........... 5.3 10 333 ........... 3.9 9 236 ........... 4.9 10 2

After Fastintg7 .2.6 8 312 ....... .... 4.4

Normal Ranige ..... 4.5-12.5 6-30 5-25mlU = milli-intcrnational uinits.

basic amino acids), catecholamines, stress (forexample, fever or surgical procedures) and certaindrugs (for example, L-dopa, vasopressin) ."'

In addition, the secretory pattern of growthhormone in response to provocative stimuli ap-pears to vary among obese and nonobese per-sons.7"9' In obese persons, little or no rise ingrowth hormone has been reported after fastingfrom 14 to 38 days.'; 778 Conversely, in otherstudies mean serum growth hormone values rosewithin three days and then fell in nonobese per-sons during fasting from three to ten days.'60.80'91The progressive rise in the level of growth hor-mone beyond day 10 is surprising in view of theprevious reports, but we are unaware of growthhormone determinations in nonobese persons fast-ing beyond ten days.

In an interesting study by Merimee and co-workers,'2 six normal and ten growth hormone-deficient dwarfs fasted for six days. Four of thegrowth hormone-deficient dwarfs received growthhormone replacement during the fasting period.Glucose levels fell 15 mg per dl in the normal andgrowth hormone-treated dwarfs but fell 50 mgper dl in the untreated dwarfs. The insulin levelalso fell whereas free fatty acid and serum ketoneconcentrations increased to a greater degree in theuntreated dwarfs compared with the normal andtreated dwarfs. Although growth hormone mayhave a lipolytic effect, these studies suggest thatit is not primary. The higher level of free fattyacids and ketones noted in the untreated dwarfswas probably related to the lower plasma insulinlevels. Nevertheless, it is apparent that glucose

homeostasis during fasting is dependent in parton the presence of growth hormone.93

Thyroid Hormone

Values for serum thyroxine (T4) in our subjectover the fasting and realimentation periods areshown in Table 5. The T4 level showed only aslight decline from the early to the late fastingperiods, and remained depressed at the end of thefirst week of realimentation. Serum triiodothy-ronine (T,), thyrotropin (thyroid-stimulatinghormone, or TSH) and reverse T, were notmeasured.

In starvation and fasting states, T4 has beenreported to be unchanged,94 increased slightly95or decreased slightly,91 whereas serum T, fallsdramatically.95 Spaulding and colleagues96 andPortnay and associates"5 showed a reduction offree T, levels by approximately 50 percent inpersons who fasted for one to four weeks. Thisreduction in T, is due to an increased productionof reverse T3, an inactive metabolite, and to alesser extent to a decrease in the peripheral con-version of T, to Ti.97 It also appears to be relatedto the carbohydrate content of the diet.96'98Spaulding and co-workers96 were able to preventthe fall of T, levels in persons fed hypocaloricdiets containing at least 50 grams of carbohydratebut not in the same persons fed hypocaloric pro-tein, fat or mixed protein-fat diets.

Despite the fall in T:, levels, clinical hypothy-roidism does not develop. Thyrotropin values donot rise, as might be expected in primary thyroiddysfunction; in fact, basal TSH concentrations maydecrease in short-term fasting98 or remain un-changed in prolonged (more than three weeks)fasting.!' In addition, TSH response to thyrotropin-releasing hormone infusions may be blunted 9899or unchanged.95

The diversion of T, metabolism from T, toreverse T: is an adaptive mechanism that reducescaloric requirements by lowering the basal meta-bolic rate and thereby indirectly reducing the needfor glucose derived from protein catabolism. Theprotein-sparing effect of this physiologic fall inT:; has been well studied.94. 00 In obese personsgiven physiologic doses of exogenous T:, to pre-vent the normal fall of the T, level during fasting,a significant increase in total urinary nitrogenexcretion has been found.100 No change in totalurinary excretion of nitrogen occurs in personsreceiving normal nutrition given similar doses.'00In another study of lean fasting men given 5 mg

390 NOVEMBER 1982 * 137 * 5

FASTING

of T3 every 3 hours for 80 hours to maintainnormal serum T, levels, excretion of urea in-creased 9.1 percent from earlier fasting controlvalues.4 Another marker of protein catabolism,3-methylhistidine, a component of actin and myo-sin that cannot be used again for protein synthesisand is excreted almost entirely in the urine, hasbeen shown to increase paralleling nitrogen lossesin fasting persons in response to exogenouslyadministered T,.100,101

In persons given larger doses of T, (150 mgevery 12 hours) for 72 hours before and duringa 72-hour fast, excretion of urea increased 2 to21/2 times whereas creatinine excretion increasedsix to nine times above control levels.'02 In addi-tion, plasma glucose, free fatty acids, serum ke-tones and urinary ketone excretion increased sig-nificantly, suggesting accelerated gluconeogenesis,lipolysis, ,8-oxidation and ketogenesis in responseto exogenous T, in a fasting but not a fed state.'01

In anorexia nervosa, as in fasting and othermalnourished states, T4 and T, levels are reducedand TSH levels are unchanged, whereas reverse T,values may be increased.103-'05 In six patients withanorexia nervosa in a study by Moshang and co-workers,'03 T4 levels were reduced slightly whereasT, levels were 50 percent lower than the levels ofnormal control subjects. The basal TSH concen-tration and response to thyrotropin-releasing hor-mone were not different in anorexic patients whencompared with normal control subjects.

GonadotropinsSerum luteinizing hormone and follicle-stimu-

lating hormone (FSH) values are shown in Table5. Both hormone levels fell during fasting and

remained low after the first week of realimenta-tion.We are unaware of comparative findings in

nonobese men during a similar period. Many ofthe data on gonadotropin response to weight losscomes from studies of patients with anorexia ner-vosa and self-imposed nonpsychopathologic weightloss or simple weight loss. Boyar and colleagues'06studied the secretory pattern of luteinizing hor-mone in nine patients with anorexia nervosa bymeasuring luteinizing hormone levels at 20-minute intervals for 24 hours. They found a lu-teinizing hormone secretory pattern resemblingthat of prepubertal and pubertal children thatreverted to a "mature" pattern with weight gain.More recent studies have reported low levels ofserum luteinizing hormone and FSH'04 in patientswith anorexia nervosa with a delayed response toexogenous luteinizing hormone-releasing hor-mone.'07-'09 A delayed response to luteinizinghormone-releasing hormone has also been notedin simple weight loss, but the response was inter-mediate in extent between that in anorexia ner-vosa patients and normal persons.'09 The responseto luteinizing hormone-releasing hormone in bothconditions of weight loss returns to normall"0 orbecomes supranormal'08 with weight gain, butresumption of menstruation in anorexia nervosamay not occur immediately, suggesting that otherfactors (most likely psychologic) are also in-volved.'0' Thus it appears that hypothalamic dys-function in patients with anorexia nervosa and toa lesser degree in patients who have undergonenonpsychopathologic weight loss is related to theextent of weight loss.

Frisch and McArthur"' postulated that a mini-mal weight-for-height ratio representing a critical

TABLE 6.-Serum Sodium (Na+), Potassium (K+), Magnesium (Mg++), Calcium (Ca++)Phosphorus (P), Zinc (Zn) and Uric Acid Levels Before, During and After Fasting

Day of Na+ K+ Mg++ Ca++ P Zn Uric acidStudy (mEq/liter) (mEqiliter) (mg/dl) (mg/dl) (mg/dl) (Ag/dl) (mitg/dl)

Before Fasting . 138 4.6 1.7 10.3 3.6 104 5.5

Fasting5 .. . 13412 .......... 13219 .......... 13126 ........... 13033 .......... 13436 .......... 122

4.8 1.4 9.63.9 1.4 10.14.1 1.2 10.04.7 1.5 10.54.8 1.5 10.2... 1.6 9.8

2.6 255 11.22.6 ... 12.63.0 342 12.52.8 307 10.53.8 284 8.43.0 364 8.0

After Fasting7 .......... 136 5.3 1.6 9.1 3.0 117 2.012 .......... 139 4.3 ... 9.4 4.0 ... 3.5

NormalRange .. (134-146) (3.5-5.3) (1.5-2.9) ( 8.8-10.8) (2.0-4.7) ( 80-120) ( 2.5-8.5)

THE WESTERN JOURNAL OF MEDICINE 391

FASTING

adipose store must be attained before onset andmaintenance of normal menstrual cycles. As withanorexia nervosa, simple weight loss and pro-tracted strenuous exercise all deplete adiposestores, resulting in menstrual irregularities. Amen-orrhea, oligomenorrhea and anovulatory cycleshave been reported in long distance runners,112"113ballet dancers,"4 and female participants in stren-uous sports,"-5 as well as in cases of anorexianervosa and simple weight loss. Because infantsurvival depends on birth weight, which is affectedby maternal weight both before and during preg-nancy, successful reproduction including lactationdepends on adequate matemal energy stores. Tele-ologically, this represents an adaptive mechanismthat limits reproduction when body energy storesare suboptimal.1"6

Whether or not the changes in luteinizing hor-

NETURINARY Ca"EXCRETION(mg/day)

80 160-

iC

E10.0SERUM Co'

[9.0 (mg dl)

-8.0NET

URINARY Mg"EXCRETION(mg/day)

80 -

40 0"

60 4F3.0

SERUM Mg'2.0 (mg dl)

1.0TOTALURINARY

PHOSPHORUSEXCRETION(mg/day)1000-

900-

800-

700-

600- 04

____ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ SERUM P500- 3.0 (mg dl)400- 2.0

5 10 15 20 25 30 35DAY OF FAST

Figure 8.-Net urinary calcium (Ca++) and magnesium(Mg++) excretion and total urinary phosphorus (P) ex-cretion over the fasting period. Serum levels are shownon the right.

mone or FSH levels that we observed are consistentfindings in fasting nonobese men and are analo-gous to the changes seen in women needs to bestudied further. Changes commonly seen in menduring periods of reduced caloric intake includeloss of libido, decreased volume of prostatic fluid,and decreased sperm number and motility.'3

Mineral ChangesPotassium

Serum potassium levels remained essentiallyunchanged in our subject (Table 6), but therewas a net total urinary loss of potassium of 37.6mEq per day for the first ten days or 729.6 mEqover the entire 36-day fast. Serum potassiumlevels may decline slightly, but rarely fall below3.0 mEq per liter even after two or more monthsof unsupplemented fasting.86 Urinary potassiumlosses observed by others86 in the early fastingperiod (first ten days) were similarly large, aver-aging 33 to 41 mEq per day in lean persons. Con-solazio and associates"7 noted a mean loss of 39.1mEq per day during a ten-day fast in six normalmen. Benedict9 reported a similar pattern ofurinary potassium excretion with an average dailyloss of 19.9 mEq per day in a 31-day fast. Inobese persons fasting a month or longer, potas-sium losses are less than half those of lean per-sons.86 Because net potassium loss is primarily fromlean tissue, these decreased losses in obese personsmay represent more efficient protein sparing asfat stores are mobilized.

MagnesiumSerum magnesium levels were remarkably

stable, whereas urinary excretion of magnesiumincreased over the first five days and then fellgradually to approximately 2 to 3 mEq per dayby the end of the fasting period (Figure 8). Totalnet urinary magnesium excretion equaled 2.6 mEqper day or 93.6 mEq over the 36-day fast.Magnesium deficiency in persons with protein-

calorie malnutrition is well recognized."8-'20 Signsand symptoms compatible with magnesium defici-ency include weakness, emaciation, anorexia, in-somnia, hyperirritability, atrophic skin changesand hypocalcemia.12' Electrocardiographic changesinclude nodal or sinus tachycardia and flat orinverted T waves in the lateral precordial leads.'2'In children with severe protein-calorie malnutri-tion and clinical signs and symptoms of magnesiumdeficiency, magnesium-supplemented realimenta-tion results in dramatic and rapid improvement in

392 NOVEMBER 1982 * 137 * 5

FASTING

serial electrocardiograms along with a return ofappetite, resumption of a normal sleep pattern andstabilization of vital signs.12'

In cases of acute starvation, evidence of mag-nesium deficiency generally is not seen. In obesepersons fasting up to 60 days, serum levels maybe slightly increased, decreased or remain thesame.86 Consolazio and colleagues"17 observed apattern of urinary magnesium excretion duringfasting that was similar to our subject's. Bene-dict9 reported an average magnesium loss of 6.0mEq per day over a 31-day fast. Gamble and co-workers'22 noted a net total loss of 51.2 mEq ofmagnesium after a 15-day fast of nonobese epilep-tic children, whereas after 15 days in our study nettotal magnesium loss equaled 50.1 mEq. Urinarymagnesium excretion is somewhat higher in obesepersons, averaging 13 mEq per day over the firstseven days, thereafter receding to a stable mini-mum excretion of 7 to 10 mEq per day.86

CalciumIn our subject, serum calcium levels fell slightly

(Figure 8) by the third week but returned towardthe baseline level by the end of the fasting period.Serum calcium levels have not been reported to besignificantly altered by fasting, probably due tothe large bony reserves. Urinary excretion of cal-cium increased steadily through the second weekof fasting and then fell gradually before stabilizingat around 4 to 5 mEq per day (Figure 8). Theaverage net urinary calcium excretion for the 36-day fast was 5.3 mEq per day or 190.8 mEq.

Calcium losses during fasting vary. The calciumloss in our subject compared quite favorably withfindings in nonobese fasting persons.9"'17"22 Con-solazio and co-workers"17 reported a 6.4 mEqdaily loss during a ten-day fast of nonobese menthat was comparable with a loss in our study of5.3 mEq per day. Benedict9 noted a net urinarycalcium loss of 10.9 mEq per day over the 31-dayfast of nonobese Mr. L. Gamble and colleagues'22reported a total urinary loss of calcium of 51.2mEq at day 15 in four epileptic children, whichwas comparable with the 50.1 mEq loss over thesame time period in our subject. In obese subjects,Drenick8" reported total urinary losses between550 and 900 mEq (11 to 18 mEq per day) duringa 50-day fasting period with a pattern of excretionsimilar to that of magnesium. In another study ofthree obese women, net calcium excretion duringfasting periods of 12, 20 and 24 days amounted

to total losses of 3.5, 10.2 and 14.7 mEq per day,respectively.'23The source of this calcium is presumed to be

bone, though actual analysis of bone for calciumcontent change during fasting has not been carriedout in humans.86 Osteoporosis with hypercalciuriais a well-documented consequence of immobili-zation.'24 Therefore, considerable variation in cal-cium losses might occur between physically activeversus inactive fasting persons. Our subject wasfully ambulatory throughout the fasting period, asare most persons studied during fasting.

PhosphorusSerum phosphorus levels and total urinary

phosphorus excretion in our subject are shown inFigure 8. Serum phosphorus levels did not changesignificantly. Peak urinary phosphorus losses oc-curred on days 4 through 6, decreasing steadilythereafter to approximately 0.5 gram per day bythe end of the fast.

Phosphate losses during fasting in obese per-sons are initially quite high, up to 80 mEq perday, before falling to average daily losses of 20to 30 mEq after 15 to 20 days.86 Rapoport andassociates125 noted similar losses closely parallel-ing the curve of titratable urinary acidity and sug-gested that phosphate might play a role in buffer-ing the metabolic acidosis of starvation.

Because sufficient quantities of phosphorus arereadily available in almost all foodstuffs, dietaryphosphorus deficiency under normal conditions isuncommon in humans.126 However, a phosphorus-depletion syndrome from prolonged antacid ther-apy, chronic alcoholism, diabetic ketoacidosis,thermal burns, hyperalimentation or severe res-piratory alkalosis has been described.'26-128

ZincSerum zinc levels in our patient are shown in

Table 6. A prompt and sustained increase wasnoted throughout the fasting period. With alimen-tation, serum levels fell to within the normalrange. Urinary excretion of zinc was not measuredin our subject.Few studies of zinc metabolism during fasting

have been reported. We are unaware of any suchstudies in nonobese persons fasting for prolongedperiods. Spencer and co-workers129 reported atWofold increase in urinary zinc excretion in thefirst six days of total fasting in an obese person.Thereafter, zinc excretion remained high, averag-ing a 4.6 mg per day loss throughout a 60-day

THE WESTERN JOURNAL OF MEDICINE 393

FASTING

starvation period. Despite these large urinarylosses, serum zinc levels rose slightly, but not tothe extent observed by us. The source of this zincis presumed to be from tissue catabolism andbone resorption.

Zinc is an essential cofactor or forms a metal-loenzyme for more than 70 known enzymes.""t'It plays a role in protein, carbohydrate, lipid, andnucleic acid synthesis and degradation. An excel-lent review of zinc metabolism and its clinicalimplications has been published recently.132

Zinc deficiency was first suspected in 1961 byPrasad,1'' who reported a syndrome of dwarfism,hypogonadism, hepatosplenomegaly and parakera-tosis in men from Iran. Zinc-deficient states havesince been reported in a variety of clinical condi-tions. Zinc deficiency has been associated withabnormal growth, abnormal sexual maturationand function, anorexia, hypogeusesthesia, dys-geusia, hyposmia, dysosmia and impaired woundhealing."2"'l2 3 Total body zinc stores are about1.5 to 2.5 grams with about 60 percent found inmuscle and 30 percent found in bone."1'".14 Undernormal conditions, these reserves are not thoughtto be readily available, thereby necessitating aminimum daily requirement. For adults this isabout 15 mg per day, increasing to 20 to 25 mgper day during pregnancy or lactation.132

Uric Acid

In our subject, serum uric acid levels roserapidly over the first two weeks, stabilized duringthe third week and fell thereafter to the upperlimit of the normal range (Table 6). Urinaryexcretion of uric acid averaged 400 mg per dayafter the first week of fasting and changed verylittle thereafter (Figure 5). Most other studieshave reported urinary uric acid excretion to de-crease with fasting.'"'13; This fall in serum uricacid that occurred in our patient while renal ex-cretion was stable may represent decreased uricacid production as protein-sparing mechanismsare activated later in fasting.

Hyperuricemia is a well-established conse-quence of fasting."36-"38 In a nonobese personstudied in the last two days of a 45-day fast, aserum uric acid level of 9.0 mg per dl (normal 3to 4 mg per dl) was recorded." We are otherwiseunaware of serum uric acid levels measured innonobese persons during prolonged fasting. Inanother study of obese patients who fasted for upto four months, serum levels of uric acid in-creased progressively for the first 15 to 20 days

to levels of 12 to 18 mg per dl (normal in men,4.0 to 8.5 mg per dl) reaching an average maxi-mum of 21.8 mg per dl as fasting extended beyondtwo months.1"9

Explanations for the hyperuricemia of fastinginclude increased production140 or decreased ex-cretion due to decreased glomerular filtrationrate,'" altered renal tubular transport systems""or ketoacidosis.'14 Uric acid and keto acids arethought to compete for renal tubular transportsites. Infusions of /-hydroxybutyrate to simulatethe ketonemia of starvation have been shown toproduce a pronounced renal retention of uricacid.'141'42 Acute episodes of gouty arthritis andurate nephrolithiasis with subsequent renal in-sufficiency have also been reported."9'42 Pro-benecid and allopurinol have been used to controlthe hyperuricemia of fasting and prevent thesecomplications,'4' but were not used in our study.Psychologic and Neurologic EffectsOur subject remained lucid throughout the fast

and maintained a rigorous schedule of daily meet-ings, conferences and worship while keeping adetailed journal of activity and subjective responseto physical changes. Appetite was noted to dimin-ish, but total anorexia did not develop. The sightand smell of food remained subjectively pleasant.

In conventional short-term calorie-deficientdiets, persistent hunger has been a major obstacleto patient compliance. However, loss of appetite(after one to four days) along with a sense ofwell-being has been reported frequently in per-sons on short total fasts for weight reduc-tion.1- "'44 Others'8 have reported euphoria with-out total anorexia. Ketosis, which develops rapidlyduring fasting, was commonly believed to be re-sponsible for the anorexia.'; More recently, /B-endorphin, an endogenous opiate that has beenlinked to feeding regulation and satiety, has beenpostulated to be involved in this physiologic adap-tation to fasting.'14The sense of well-being that may occur during

short-term total fasting is in contradistinction tothat seen during prolonged periods of semistarva-tion when mental lethargy, apathy and irritabilityare common.li1.3 To explain the euphoria,Bloom" postulated that accumulation of aceto-acetic acid produces a mild intoxication similar toethanol. Phillips'4'; from studies in animals specu-lated that the accumulation of isopropyl alcoholin neural tissue might be responsible for fasting-induced religious, mystical or hallucinatory ex-

394 NOVEMBER 1982 * 137 * 5

FASTING

periences. One must also consider the positivepsychologic benefits of significant daily weightloss in persons who have had lifelong histories ofobesity previously refractory to any treatment.

Electroencephalographic studies in fasting per-sons have been limited. Owen and associates65reported no change in the findings on electroen-cephalograms of three obese persons who fastedfor 38 to 41 days. In patients who fasted forpsychosomatic disorders, fast-wave activity onelectroencephalograms was reported to increase.547In studies of children suffering from kwashiorkor,electroencephalographic tracings showed abnor-mal slow-wave frequencies'48 or a high incidenceof abnormal tracings in the temporal lobe.'49In both studies a return of the electroencephalo-graphic findings toward normal was reported withnutritional rehabilitation.

In other types of dieting, including liquidprotein and protein-sparing modified fasting,anorexia is purported to be a prominent fea-ture.'50 i In a study of patients with Prader-Williobesity who fasted on a protein-sparing hypo-caloric regimen, the high degree of outpatientcompliance obtained in these mentally deficientpatients, who do not normally experience satiety,was believed to be due to an appetite-suppressanteffect of the ketogenic diet regimen.15'

Medical Complications of Prolonged FastingComplications reported during prolonged fast-

ing for weight reduction are summarized in Table7. Although prolonged fasting is generally welltolerated with few and relatively minor complica-tions,152 several reports of death after or duringtotal fasting have appeared.""5"5-'6' In additionto morbid obesity, two of six reported fatal caseshad severe prefast symptoms of congestive heartfailure (which initially improved with fasting) andone had focal stenosis of the coronary arteries atautopsy.157'60 In another case a small bowel ob-struction developed in the fasting person and deathfrom complications occurred on the 13th day.153An abrupt onset of renal failure followed by deathin another patient after 14 days of a total fast hasbeen reported; chronic glomerulonephritis wasfound at autopsy.'6' In the sixth fatal case, the pa-tient, who otherwise was in good health, had beengiven small amounts of protein supplements (es-sential amino acids) for 103 days of a 21 0-day fast,but died of intractable ventricular dysrhythmias onthe eighth day of realimentation."8 In this case,as is common in deaths of patients while on liquid

TABLE 7.-Complications During ProlongedAcaloric Fasting

Complication References

NonfatalHeadaches ............ ........... 15-18,152,153Light-headedness ........ .......... 16,18,152Nausea .......................... 15,16,144,152Abdominal pain ........ ........... 153Weakness ........................ 16,152,154Cramps .. ................. 86,152Orthostatic hypotension ............ 17,152,153Acute gout ........... ...... 17,139,152Urate nephrolithiasis ............... 139Renal insufficiency ................. 139Oliguria ........ ......... 18,144,152,153Edema ...... ........... 18Atrial flutter ............. .... 152Anemia ....... .......... 17,144Amenorrhea .............. ... 13,111Alopecia ........ ......... 154Porphyria ......... ........ 155Parotitis ........ ......... 18Polyneuritis ........... ...... 154,156Vitamin deficiency ................. 17,154

FatalIntractable ventricular arrhythmia .... 157-159Lactic acidosis ................. 160Small bowel obstruction

with complications ............... 153Renal failure ............. .... 161

protein fasts,"162 an otherwise unexplained pro-longation of the QT interval was reported alongwith gross fragmentation of myocardial fibrils atnecropsy. Although the cause of the dysrhythmiasin these patients is unknown, perhaps this caserepresents the first reported though unrecognizeddeath during protein-supplemented fasting.

Liquid protein diets, recently promoted heavilyin the lay press' ° for weight reduction, are nowknown to be associated with serious complicationsincluding intractable ventricular dysrhythmias andsudden death."6'"' Isner and colleagues'6 re-viewed findings on 17 unexpected deaths in other-wise healthy obese persons using liquid proteindiets. In all of nine patients for whom adequateelectrocardiographic information was available,the QT interval was prolonged. Seven of the casesdid not have the usual causes of QT interval pro-longation-that is, hypocalcemia, hypomagnese-mia, drugs or congenital anomaly. In anotherstudy of three persons with no previous history ofcardiac disease who were on a liquid protein-fasting regimen, the QT intervals were prolonged,the ST segments and T waves were abnormal,and intermittent syncopal episodes due to ven-tricular tachycardia and ventricular fibrillationoccurred for up to three months after discontinua-

THE WESTERN JOURNAL OF MEDICINE 395

FASTING

tion of the diet. '66 All patients had electrocardio-graphic features of atypical ventricular tachycar-dia (torsades de pointes*); two of the patientsdied.'66 These studies suggest a causal relation-ship between liquid protein diets and delayed re-polarization (prolonged QT interval), seriousventricular arrhythmias and risk of sudden death.

In an effort to assess the dysrhythmogenicity ofliquid protein diets, six obese patients were given300 kcal per day of a commercially preparedliquid protein hydrolysate for 40 days and wereobserved weekly with 12-lead electrocardiographicand 24-hour Holter monitoring.'67 No abnormali-ties were seen using standard 12-lead electro-cardiographic monitoring in any patient before,during or after the fasting period. However, with24-hour Holter monitoring, persistent and mul-tiple ventricular dysrhythmias occurred in threeof six patients after the tenth day of supplementedfasting. These dysrhythmias were noted to increasein frequency and complexity as the fasting periodprogressed. After resumption of normal diet, nofurther disturbances were seen with either stan-dard 12-lead electrocardiograms or Holter moni-toring in any of the patients. Although these find-ings are intriguing, unfortunately no control groupwas examined nor are there available comparativestudies of Holter monitoring in persons undergo-ing other forms of dietary restriction such as totalfasts, protein-sparing modified fasts or hypoca-loric mixed diets. Although the cause of the life-threatening dysrhythmias seen in patients onprotein diets is unknown, deficiencies of trace ele-ments,'68"6('9 micronutrients17° and essential aminoacids,'7' as well as electrolyte disturbances1721 73and biologically poor protein sources, 74"175 haveall been suggested.

SummaryEarly in fasting, weight loss is rapid, averaging

0.9 kg per day during the first week and slowingto 0.3 kg per day by the third week. During theperiod of rapid weight loss, there is significantnegative sodium balance, probably due to lossesof the sodium salts of keto acids in the urine. Asmild starvation ketoacidosis develops, ammoniaproduction is stimulated, providing ammoniumfor excretion with keto acids and thus sparingsodium loss. This leads to a decrease in the rate

*Torsades de pointes means "twisting of the points" anid is be-lieved to represent an especially malignant form of ventriculartachycardia characteristically seen in association with a prolongedQT interval in which polarity of ventricular complexes swings be-tween the positive and the negative directions.

of weight loss. Carbohydrate-free fasts tend tocause orthostatic hypotension due to the sodiumlosses plus a degree of autonomic insufficiency.Other physical features such as the amplitude andaxis on the electrocardiogram change, probablyreflecting loss of cardiac mass, and bradycardiadevelops.

The early days of fasting are characterizedmetabolically by a high rate of gluconeogenesis,chiefly with the use of amino acids, especiallyalanine, as substrates. The stimulus for glucone-ogenesis appears to be decreased insulin produc-tion and increased glucagon. As fasting continues,progressive ketosis develops due to mobilizationand oxidation of fatty acids. At higher blood levelsof ketones, the brain is able to use ketones as aprimary energy source, thereby decreasing theneed for gluconeogenesis. The specific feedbackis probably by ketones on release of alanine frommuscle. The ketotic phase of fasting is then asso-ciated with protein sparing. Lean persons becomeketotic earlier than obese persons, and womenbecome ketotic more rapidly than men.

Other hormonal changes occur. Serum levels ofT, promptly fall with a reciprocal rise in reverseT3, which contributes to protein sparing. Changesin the blood level of growth hormone during fast-ing are varied and may differ depending onwhether the person is obese or nonobese. Changesin the blood level of gonadotropin are not wellcharacterized; luteinizing hormone and FSH levelsfall, at least in the patient reported herein.

Potassium losses decrease after ten days offasting though some losses persist. Magnesiumcalcium and phosphorous losses are minimal afterthe first week.

Changes in trace metal balance are poorly de-fined. Serum zinc levels rose through the fastingperiod in the patient reported herein, but thesignificance of this change is unknown.

Hyperuricemia occurs in fasting obese personsand also occurred in our nonobese subject. Thisis probably due to increased production of uricacid from tissue catabolism and decreased urinaryexcretion of uric acid from competitive inhibitionof tubular uric acid secretion.

The subjective psychologic effects of fastingmay produce a sense of well-being or euphoria.Neurologically, there is evidence that ketosis mayincrease seizure thresholds in patients with epi-lepsy. Electroencephalograms in chronic protein-calorie malnutrition show diffuse slowing andabnormal temporal lobe tracings.

396 NOVEMBER 1982 * 137 * 5

FASTING

Rare medical complications of short-term fast-ing include gout, urate nephrolithiasis, posturalhypotension and cardiac dysrhythmias. The par-ticular association of liquid protein-supplementedfasting and sudden cardiac death is well reported,though the mechanism is still unknown.

REFERENCES1. Arbesmann R: Fasting and prophecy in pagan and Christian

antiquity. Traditio 1951; 7:1-712. MacDermot V: The Cult of the Seer in the Ancient Middle

East. Berkeley, University of California Press, 19713. Maulana Muhamniad Ali: The Religion of Islam: A Com-

prehensive Discussicn of the Sources, Principles and Practices ofIslam. Lahore, Pakistan, Ryson Printing Press, 1936

4. Haskell CC: Perfect Health-How to Get It and How toKeep It. Lcndon, L N Fowler, 1901

5. Sinclair U: The Fasting Cure. New York, Mitchell Kenner-ley, 1911

6. Dr. Tanner's fast. Br Med J 1880 Jul 31; 2:1717. Paton DN, Stockman R: Observations on the metabolism of

man during starvation. Proc R Acad Edinb 1888-1889; pp 121-1318. Rcbins GN: The fasting man. Br Med J 1890 Jun 21; 1:

1444-14469. Benedict FG: A Study of Prolonged Fasting, Publication No.

203. Washington DC, Carnegie Institute, 191510. Penny F: Notes on a thirty days' fast. Br Med J 1909 Jun

12; 1: 1414-141611. Sunderman FW: Studies in serum electrolytes-XIV.

Changes in blood and body fluids in prolonged fasting. Am J ClinPathol 1947 Mar; 17:169-180

12. Gamble JL: Physiological information gained from studiescn the life raft ration. Harvey Lect 1946-1947; 42:247-273

13. Keys A, Brozek J, Henschel A: The Biology of HumanStarvation-Vols I, II. Minneapolis, University of Minnesota Press,1950

14. Folin 0, Denis W: On starvation and obesity, with specialreference to acidosis. J Biol Chem 1915; 21:183-192

15. Bloom WL: Fasting as an introduction to the treatment ofobesity. Metabolism 1959 May; 8:214-220

16. Duncan GG, Jenson WK, Cristofori FC, et al: Intermittentfasts in the correction and control of intractable obesity. Am JMed Sci 1963 May; 245:515-520

17. Drenick EJ, Swenseid ME, Blahd WH, et al: Prolonged star-vation as treatment for severe obesity. JAMA 1964 Jan 11: 187;100-105

18. Thomson TJ, Runcie J, Miller V: Treatment of obesity bytotal fasting for up to 249 days. Lancet 1966 Nov 5; 2:992-996

19. Stewart WK, Fleming LW: Features cf a successful thera-peutic fast of 382 days' duration. Postgrad Med J 1973 Mar; 49:203-209

20. Guelpa and Marie, 1910, cited by Keith HM: ConvulsiveDisorders in Children: With Reference to Treatment With Keto-genic Diet. Boston, Little Brown, 1963

21. Geyelin HR: Fasting as a method for treating epilepsy. MedRec 1921 Jun; 99:1037-1038

22. Livingston S: Comprehensive Management of Epilepsy inInfancy, Childhood, and Adolescence. Springfield, Charles CThomas, 1972

23. Jack HA (Ed): Gandhi Re,ader: A Source Book of HisLife and Writings; Mohandas K. Gandhi. New York, AMS Press,1965

24. MacSwiney dies after fasting 74 days; npws excites Ireland;riot in Belfast; second hunger striker is dead in Cork; JosephMurphy dies of 76 days' hunger strike, the second prisoner tosuccumb in Cork jail. New York Times 1920 Nov 26; 70:1

25. Downie L: Prisoners end fasting in Belfast. The WashingtonPost 1981 Oct 4, p 1

26. Hales CN, Randle PJ: Immunoassay of insulin with insulin-antibody precipitate. Biochem J 1963 Jul; 88:137-146

27. Unger RH, Eisentraut AM, McCall MS, et al: Glucagonantibodies and an immunoassay for glucagon. J Clin Invest 1961Jul; 40: 1280-1289

28. Schalch DS, Parker ML: A sensitive double antibody im-munoassay for human growth hormone in plasma. Nature 1964Sep 12; 203:1141-1142

29. Stegink LD, Filer LJ Jr, Baker GL: Effect of aspartameand aspartate loading upon plasma and erythrocyte free aminoacid levels in normal adult volunteers. J Nutr 1977 Oct; 107:1837-1845

30. Felig P: Starvation, In DeGroot LJ, Cahill GF Jr, et al(Eds): Endocrinology-Vol 3. New York, Grune & Stratton,1979, pp 1927-1940

31. Theorell T, Kjellberg J, Palmblad J: Electrocardiographicchanges during total energy deprivation (fasting). Acta MedScand 1978; 203:13-19

32. Slany J, Mosslacher H, Bodner P, et al: KardiovaskulareFolgen einer Nullkaloriendiat bei Adiposen. Wien Klin Wochen-schr 1974 Aug; 86:423-424

33. Winick M (Ed): Hunger Disease-Studies by the JewishPhysicians in the Warsaw Ghetto. New York, John Wiley & Sons,1979

34. Consolazio CF, Nelson RA, Johnson HL, et al: Metabolicaspects of acute starvation in normal humans: Performance andcardiovascular evaluation. Am J Clin Nutr 1967 JulI; 20:684-693

35. DeHaven J, Sherwin R, Hendler R, et al: Nitrogen andsodium balance and sympathetic-nervous-system activity in obesesubjects trcated with a low-calorie protein or mixed diet. N EnglJ Med 1980 Feb 28; 302:477-482

36. Landsberg L, Young JB: Fasting, feeding and reguLlation ofthe sympathetic nervous systenm. N Engl J Med 1978 Jun 8;298:1295-1301

37. Ellis LB: Electrocardiographic abnormalities in severemalnUtrition. Br Heart J 1946; 8:53-61

38. Heymsfield SB, Bethel RA, Ansley JD, et al: Cardiacabnormalities in cachectic patients before and during nutritionalrepletion. Am Heart J 1978 May; 95:584-594

39. Thurston J, Marks P: Electrocardiographic abnormalitiesin patients with anorexia nervosa. Br Heart J 1974 Jul; 36:719-723

40. Blackburn GL, Bistrian BR, Maini BS, et al: Nutritionaland metabolic assessment of the hospitalized patient. JPEN1977 Feb; 1:11-22

41. Bloom WL, Mitchell W Jr: Salt excretion of fasting patiqpts.Arch Intern Med 1960 Sep; 106:71-76

42. North KAK, Lascelles D, Coates P: The mechanisms bywhich sodium excretion is increased during a fast but reduced onsubsequent carbohydrate feeding. Clin Sci Mol Med 1974 Apr;46:423-432

43. Sigler MH: The mechanism of the natriuresis of fasting. JClin Invest 1975 Feb; 55:377-387

44. Kolanowski J, Bodson A, Desmecht P. et al: On the rela-tionship between ketonLuria and ratriuresis duLring fasting and uponrefeeding in obese patients. EuLr J Clin Invest 1978 Oct; 8:277-282

45. Saudek CD, Boulter PR, Arky RA: The natriuretic effect ofglucagon and its role in starvation. J Clin Endocrinol Metab 1973Apr; 36:761-765

46. Saudek CD, Botulter PR, Knopp RH, et al: Sodium reten-tion acconmpanying insulin treatment of diabetes mellituLs. Diabetes1974 Mar; 23:240-246

47. Bloom WL: Inhibition of salt excretion by carbohydrate.Arch Intern Med 1962 Jan; 109:80-86

48. Veverbrants E, Arky RA: Effects of fasting and refeeding-I. Studies on sodium, potassiulm and water excretion on a constantelectrolyte and fluid intake. J Clin Endocrinol 1969 Jan; 29:55-62

49. Botulter PR, Hoffman RS, Arky RA: Pattern of sodiuLmexcretion accompanying starvation. Metabolism 1973 May; 22:675-683

50. Spark RF, Arky RA, Boulter PR, et al: Renin, aldosteroneand glucagon in the natriuresis of fasting. N Engl J Med 1975Jun 19; 292:1335-1340

51. Cahill GF Jr, Owen OE, Morgan AP: The consumption offuels during prolonged starvation. Adv Enzyme Regul 1968: 6:143-150

52. Garrow JS, Fletcher K. Halliday D: Body composition insevere infantile malnutrition. 'J Clin Invest 1965 Mar; 44:417-425

53. Saudek CD, Felig P: The metabolic events of starvation.Am J Med 1976 Jan; 6(0:117-126

54. Cahill GF Jr, Owen OE: Starvation and survival. TransAm Clin Climatol Assoc 1967; 79:13-20

55. Felig P: The glucose-alanine cycle. Metabolism 1973 Feb;22: 179-207

56. Cahill GF Jr: Starvation in man. N Engl J Med 1976 Mar19; 282:668-675

57. Felig P, Owen OE, Wahren J, et al: Amino acid metabolismduring prolonged starvation. J Clin Invest 1969 Mar; 48:584-594

58. Adibi SA: Metabolism of branched-chain amino acids inaltered nutrition. Metabolism 1976 Nov; 25:1287-130)2

59. Slherwin RS, Hendler RG, Felig P: Effect of ketone infusionson amino acid and nitrogen metabolism in man. J Clin Invest 1975Jun; 55:1382-1390

60. Cahill GF Jr, Herrera MG, Morgan AP, et al: Hormone-fuel interrelationships during fasting. J Clin Invest 1966 Nov; 45:1751-1769

61. Merimee TJ, Tyson JE: Stabilization of plasma glucoseduring fasting: Normal variations in two separate studies. N EnglJ Med 1974 Dec 12; 291:1275-1278

62. Merimee TJ, Fineberg SE: Homeostasis during fasting-II.Hormone substrate differences between men and women. J ClinEndocrinol Metab 1973 Nov; 37:698-702

63. Tyson JE, Austin K, Farinholt J: Estrogen modulation ofglucose homeostasis. Clin Res 1974; 22:481A

64. Owen OE, Felig P, Morgan AP, et al: Liver and kidneymetabolism during prolonged starvation. J Clin Invest 1969 Mar;48:574-583

65. Owen OE, Morgan AP, Kemp HG, et al: Brain metabolismduring fasting. J Clin Invest 1967 Oct; 46:1589-1595

66. Nosadini R, Alberti KGMM, Johnston DG, et al: The anti-ketogenic effect of alanine in normal man: Evidence for analanine-ketone body cycle. Metabolism 1981 Jun; 30:563-567

THE WESTERN JOURNAL OF MEDICINE 397

FASTING

67. Drenick EJ, Alvarez LC, Tamasi GC, et al: Resistance tosymptomatic insulin reactions after fasting. J Clin Invest 1972Oct; 51:2757-2762

68. Sapir DG, Owen OE: Renal conservation of ketone bodiesduring starvation. Metabolism 1975 Jan; 24:23-33

69. Garber AJ, Menzel PH, Boden G, et al: Hepatic ketogenesisand gluconeogenesis in humans. J Clin Invest 1974 Oct; 54:981-989

70. Owen OE, Reichard GA Jr: Human forearm metabolismduring progressive starvation. J Clin Invest 1971 Jul; 50:1536-1545

71. Deuel HJ Jr, Gulick M: Studies on ketosis-I. The sexualvariation in starvation ketosis. J Biol Chem 1932 Apr; 96:25-34

72. Bloom WL, Azar G, Clark J, et al: Comparison of meta-bolic changes in fasting obese and lean patients. Ann NY AcadSci 1965 Oct 8; 131:623-631

73. Bloom WL, Azar G, Clark JE: Electrolyte and lipid metab-olism of lean fasting men and women. Metabolism 1966 May; 15:401-408

74. Kekwick A, Pawn GLS, Chalmers TM: Resistance to ketosisin obese subjects. Lancet 1959 Dec 26; 2:1157-1159

75. Bloom WL: Fasting ketosis in obese men and women. JLab Clin Med 1962 Apr; 59:605-612

76. Flier JS, Kahn CR, Roth J: Receptors, antireceptor anti-bodies and mechanisms of insulin resistance. N Engl J Med 1979Feb 22; 300:413-419

77. Roth J, Glick SM, Yalow RS, et al: Secretion of humangrowth hormone: Physiologic and experimental modification.Metabolism 1963 Jul; 12:577-579

78. Beck P, Koumans JT, Winterling CA, et al: Studies of in-sulin and growth hormone secretion in human obesity. J Lab ClinMed 1964 Oct; 64:654-667

79. Glick SM, Roth J, Yalow RS, et al: The regulation ofgrowth hormone secretion. Rec Prog Hormone Res 1965; 21:241-283

80. Merimee TJ, Fineberg SE: Growth hormone secretion instarvation: A reassessment. J Clin Endocrinol Metab 1974 Aug;39:385-386

81. Merimee TJ, Misbin RI, Pulkkinen AJ: Sex variations infree fatty acids and ketones during fasting: Evidence for a roleof glucagon. J Clin Endocrinol Metab 1978 Mar; 46:414-419

82. Unger RH, Eisentraut AM, Madison LL, et al: Fastinglevels of growth hormone in men and women. Nature 1965 Feb20; 205:804-805

83. Forbes GB: Weight loss during fasting: Implications for theobese. Am J Clin Nutr 1970 Sep; 23:1212-1219

84. Runcie J, Hilditch TE: Energy provision, tissue utilization,and weight loss in prolonged starvation. Br Med J 1974 May 18;2:352-356

85. Forbes GB, Drenick EJ: Loss of body nitrogen on fasting.Am J Clin Nutr 1979 Aug; 32:1570-1574

86. Drenick EJ: The effects of acute and prolonged fasting andrefeeding on water, electrolyte, and acid-base metabolism, InMaxwell MH, Kleeman CR (Eds): Clinical Disorders of Fluidand Electrolyte Metabolism-3rd Ed. New York, McGraw-Hill,1979

87. Raben MS, Hollenberg CH: Effect of growth hormone onplasma fatty acids. J Clin Invest 1959 Mar; 38:484-488

88. Williams RH (Ed): Textbook of Endocrinology-5th Ed.Philadelphia, WB Saunders, 1974

89. Labhart A (Ed): Clinical Endocrinology: Theory and Prac-tice. New York, Springer-Verlag, 1976

90. Bray GA: The obese patient, chap 7, In Smith LH (Ed):Major Problems in Internal Medicine-Vol 9. Philadelphia, WBSaunders, 1976

91. Palmblad J, Levi L, Burger A, et al: Effects of total energywithdrawal (fasting) on the levels of growth hormone, thyrotropin,cortisol, adrenaline, noradrenaline, T4, T3, and rT3 in healthymales. Acta Med Scand 1977; 201:15-22

92. Merimee TJ, Felig P, Marliss E, et al: Glucose and lipidhomeostasis in the absence of human growth hormone. J ClinInvest 1971 Mar; 50:574-582

93. Felig P, Marliss EB, Cahill GF Jr: Metabolic response tohuman growth hormone during prolonged starvation. J Clin Invest1971; 50:411-421

94. Gardner DF, Kaplan MM, Stanley CA, et al: Effect of tri-iodothyronine replacement on the metabolic and pituitary re-sponses to starvation. N Engl J Med 1979 Mar 15; 300:579-584

95. Portnay GI, O'Brian JT, Bush J, et al: The effect of star-vation on the concentration and binding of thyroxine and tri-iodothyronine in serum and on the response in serum and on theresponse to TRH. J Clin Endocrinol Metab 1974 Jul; 39:191-194

96. Spaulding SW, Chopra IJ, Sherwin RS, et al: Effect ofcaloric restriction and dietary coniposition on serum Ta and re-verse Ts in man. J Clin Endocrinol Metab 1976 Jan; 42:197-200

97. Vagenakis AG, Burger A, Portnay GI, et al: Diversion ofperipheral thyroxine metabolism from activating to inactivatingpathways during complete fasting. J Clin Endocrinol Metab 1975Jul; 41:191-194

98. Azizi F: Effect of dietary composition on fasting-inducedchanges in serum thyroid hormones and thyrotropin. Metabolism1978 Aug; 27:935-942

99. Burman KD, Smallridge RC, Osburne R, et al: Nature ofsuppressed TSH secretion during undernutrition: Effect of fasting

and refeeding on TSH responses to prolonged TRH infusions.Metabolism 1980 Jan; 29:46-52

100. Vignati L, Finley RJ, Hagg S, et al: Protein concentrationsduring prolonged fast: A function of triiodothyronine levels. TransAssoc Am Physicians 1978; 91:169-179

101. Burman KD, Wartofsky L, Dinterman RE, et al: Theeffect of T3 and reverse T3 administration on muscle protein cata-bolism during fasting as measured by 3-metwhylhistidine excretion.Metabolism 1979 Aug; 28:805-813

102. Carter WJ, Shakir KM, Hodges S, et al: Effect of thyroidhormone on metabolic adaptation to fasting. Metabolism 1975Oct; 24:1177-1183

103. Moshang T Jr, Parks JS, Baker L, et al: Low serum tri-iodothyronine in patients with anorexia nervosa. J Clin Endo-crinol Metab 1975 Mar; 40:470-473

104. Hurd HP II, Palumbo PJ, Gharib H: Hypothalamic-endo-crine dysfunction in anorexia nervosa. Mayo Clin Proc 1977 Nov;52:711-716

105. Halmi KA: Anorexia nervosa: Recent investigations. AnnuRev Med 1978; 29:137-148

106. Boyar RM, Katz J, Finkelstein JW, et al: Anorexia ner-vosa: Immaturity of the 24-hour luteinizing hormone secretorypattern. N Engl J Med 1974 Oct 24; 291:861-865

107. Vigersky RA, Loriaux DL, Andersen AE, et al: Delayedpituitary hormone response to LRF and TRF in patients withanorexia nervosa and with secondary amenorrhea associated withsimple weight loss. J Clin Endocrinol Metab 1976 Oct; 43:893-900

108. Beumont PJ, George GC, Pimstone BL, et al: Body weightand the pituitary response to hypothalamic releasing hormones inpatients with anorexia nervosa. J Clin Endocrinol Metab 1976Sep; 43:487-496

109. Vigersky RA, Andersen AE, Thompson RH, et al: Hypo-thalamic dysfunction in secondary amenorrhea associated withsimple weight loss. N Engl J Med 1977 Nov 24; 297:1141-1145

110. Warren MP, Jewelewicz R, Dyrenfurth I, et al: The sig-nificance of weight loss in the evaluation of pituitary response toLH-RH in women with secondary amenorrhea. J Clin EndocrinolMetab 1975 Apr; 40:601-611

111. Frisch RE, McArthur JW: Menstrual cycles: Fatness as adeterminant of minimum weight for height necessary for theirmaintenance or onset. Science 1974 Sep 13; 185:949-951

112. Dale E, Gerlach DH, Wilhite AL: Menstrual dysfunctionin distance runners. Obstet Gynecol 1979 Jul; 54:47-53

113. Feicht CB, Johnson TS, Martin BJ, et al: Secondaryamenorrhoea in athletes. Lancet 1978 Nov 25; 2:1145-1146

114. Frisch RE, Wyshak G, Vincent L: Delayed menarche andamenorrhea in ballet dancers. N Engl J Med 1980 Jul 3; 303:17-19

115. Malina RM, Spirduso WW, Tate C, et al: Age at menarcheand selected menstrual characteristics in athletes at different com-petitive levels and in different sports. Med Sci Sports 1978 Fall;10: 218-222

116. Frisch RE: Population, food intake, and fertility. Science1978 Jan 6; 199:22-30

117. Consolazio CF, Matoush LO, Johnson HL, et al: Metabolicaspects of acute starvation in normal humans (10 days). Am JClin Nutr 1967 Jul; 20:672-683

118. Caddell JL, Goddard DR: Studies in protein-calorie mal-nutrition-I. Chemical evidence for magnesium deficiency. N EnglJ Med 1967 Mar 9; 276:533-535

119. Nichols BL, Alvarado J, Hazlewood CF, et al: Magnesiumsupplementation in protein-calorie malnutrition. Am J Clin Nutr1978 Jan; 31:176-188

120. Flink EB: Nutritional aspects of magnesium metabolism.West J Med 1980 Oct; 133:304-312

121. Caddell JL: Studies in protein-calorie malnutrition-II. Adouble blind clinical trial to assess magnesium therapy. N Engl JMed 1967 Mar 9; 276:535-540

122. Gamble JL, Ross SG, Tisdall FF: The metabolism of fixedbase during starvation. J Biol Chem 1923 Oct; 57:633-695

123. Spencer H, Lewin I, Samachson J, et al: Changes inmetabolism in obese persons during starvation. Am J Med 1966Jan; 40:27-37

124. Lee DBN, Zawada ET, Kleeman CR: The pathcphysiologyand clinical aspects of hypercalcemic disorders (Medical Progress).West J Med 1978 Oct; 129:278-320

125. Rapoport A, From GLA, Husdan H: Metabolic studies inprolonged fasting-I. Inorganic metabolism and kidney function.Metabolism 1965 Jan; 14:31-45

126. Lotz M, Zisman E, Bartter FC: Evidence for a phosphorus-depletion syndrome in man. N Engl J Med 1968 Feb 22; 278:409-415

127. Knochel JP: Hypophosphatemia (Nutrition in Medicine).West J Med 1981 Jan; 134:15-26

128. Lentz RD, Brown DM, Kjellstrand CM: Treatment of severehypophosphatemia. Ann Intern Med 1978 Dec; 89:941-944

129. Spencer H, Osis D, Kramer L, et al: Studies of zinc metab-olism in man, In Hemphill DD (Ed): Trace Substances in Environ-mental Health-Vol 5. Colombia, MO, University of Missouri, 1972

130. Ulmer DD: Trace elements. N Engl J Med 1977 Aug 11;297:318-321

131. Trace elements-Medical Staff Conference, University ofCalifornia, San Francisco. West J Med 1978 Mar; 128:223-227

398 NOVEMBER 1982 * 137 * 5

FASTING

132. Walravens PA: Zinc metabolism and its implications inclinical medicine (Clinical Nutrition Symposium). West J Med 1979Feb; 130: 133-142

133. Prasad AS (Ed): Trace Elements in Human Health andDisease-Vol 1: Zinc and Copper. New York, Academic Press,1976

134. Prasad AS, Rabbani P, Abbasii A, et al: Experimentalzinc deficiency in humans. Ann Intern Med 1978 Oct; 89:483-490

135. Lennox WG: A study of the retention of uric acid duringfasting. J Biol Chem 1925 Dec; 66:52.1-572

136. Cristofori FC, Duncan GG: Uric acid excretion in obesesubjects during periods of total fasting. Metabolism 1964 Apr;13:303-311

137. Lennox WG: Increase of uric acid in the blood duringprolonged starvation. JAMA 1924 Feb 23; 82:602-604

138. Murphy R, Shipman KH: Hyperuricemia during total fast-ing: Renal factors. Arch Intern Med 1963 Dec; 112:192-197

139. Drenick EJ: Hyperuricemia, acute gout, renal insufficiencyand urate nephrolithiasis due to starvation. Arthritis Rheum 1965Oct; 8:988-997

140. Pabico RC, Canfield CJ, Barry KG: The effects of acutetotal caloric starvation on uric acid metabolism in obese humansubjects. Clin Res 1965 Jan; 13:45A

141. Goldfinger S, Klinenberg JR, Seegmiller JE: Renal reten-tion of uric acid induced by infusion of beta-hydroxybutyrate andacetoacetate. N Engl J Med 1965 Feb; 272:351-355

142. Shapiro JR, Klinenberg JR, Peck W, et al: Hyperuricemiaassociated with obesity and intensified by caloric restriction.Arthritis Rheum 1964 Jun; 7:343

143. Drenick EJ, Fisler, JL, Dennin HF: The effect of allo-purinol on the hyperuricemia of fasting. Clin Pharmacol Ther1971 Jan-Feb; 12:68-72

144. Lawlor T, Wells DG: Fasting as a treatment of obesity.Postgrad Med J 1971 Jun; (Jun Suppl):452-458

145. Gambert SR, Garthwaite TL, Pontzer CH, et al: Fastingassociated with decrease in hypothalamic /8-endorphin. Science1980 Dec 12; 210:1271-1272

146. Phillips RW: Religious revelations and bovine ketosis (anonsacred cow). Perspect Biol Med 1978 Spring; 21:398-405

147. Suzuki J, Yamauchi Y, Yamamoto H, et al: Fasting ther-apy for psychosomatic disorders in Japan. Psychother Psychosom1979 Jan-Feb; 31:307-314

148. Engel R: Abnormal brain wave patterns in kwashiorkor.Electroencephalogr Clin Neurophysiol 1956 Aug; 8:479-488

149. Nelson GK: The electroencephalogram in kwashiorkor.Electroencephalogr Clin Neurophysiol 1959 Feb; 11:73-84

150. Linn R: The Last Chance Diet. New York, Bantam Books,1976

151. Bistrian BR, Blackburn GL, Stanbury JB: Metabolicaspects of a protein-sparing modified fast in the dietary manage-ment of Prader-Willi obesity. N Engl J Med 1977 Apr 7; 296:774-779

152. Duncan GG, Duncan TG, Schless GL, et al: Contraindica-tions and therapeutic results of fasting in obese patients. Ann NYAcad Sci 1965 Oct 8; 131:632-636

153. Runcie J, Thomson TJ: Prolonged starvation-A dangerousprocedure? Br Med J 1970 Aug 22; 3:432-435

154. Gellene R, Frank 0, Baker H, et al: B-complex vitaminsin total food deprivation. Fed Proc 1965; 24:314A

155. Knudsen KB, Sparberg M, Lecocq F: Porphyria precipitatedby fasting. N Engl J Med 1967 Aug 17; 277:350-351

156. Rooth G, Carlstrom S: Therapeutic fasting. Acta MedScand 1970 Jun; 187:455-463

157. Spencer IOB: Death during therapeutic starvation forobesity. Lancet 1968 Jun 15; 1:1288-1290

158. Garnett ES, Barnard DL, Ford J, et al: Gross fragmenta-tion of cardiac myofibrils after therapeutic starvation for obesity.Lancet 1969 May 3; 1:914-916

159. Kahan A: Death during therapeutic starvation. Lancet 1968Jun 22; 1:1378-1379

160. Cubberley PT, Polster SA, Schulman CL: Lactic acidosisand death after the treatment of obesity by fasting. N Engl JMed 1965 Mar 25; 272:628-630

161. Norbury FB: Contraindications to long-term fasting.JAMA 1964 Apr 6; 188:88

162. Follow-up on deaths in persons on liquid protein diets.MMWR 1977 Dec 30; 26:443

163. Liquid protein and sudden cardiac deaths-An update.FDA Drug Bull 1978 May-Jul; 8:18-19

164. Michiel RR, Sneider JS, Dickstein RA, et al: Sudden deathin a patient on a liquid protein diet. N Engl J Med 1978 May 4;298: 1005-1007

165. Isner JM, Sours HE, Paris AL, et al: Sudden unexpecteddeath in avid dieters using the liquid-protein-modified-fast diet(observations in 17 patients and the role of the prolonged QT in-terval). Circulation 1979 Dec; 60:1401-1412

166. Singh BN, Gaarder TD, Kanegae T, et al: Liquid proteindiets and torsade de pointes. JAMA 1978 Jul 14; 240:115-119

167. Lantigua RA, Amatruda JM, Biddle TL, et al: Cardiacarrhythmias associated with a liquid protein diet for the treat-ment of obesity. N Engl J Med 1980 Sep 25; 303:735-738

168. Hastings DH: "Liquid protein diets" and "Protein-sparingmodified fast" (Letter to the Editor). N Engl J Med 1978 Aug 24;299: 420

169. Frank A: "Liquid protein diets" and "Protein-sparingmodified fast" (Letter to the Editor). N Engl J Med 1978 Aug 24;299: 420-421

170. Moldawer LL, Beauregard K, Bistrian BR, et al: Role ofmicronutrient intake in cardiac changes produced by liquid protein.Clin Res 1979 Sep; 27:593A

171. Hilton MA: Nutritional need for sulfur amino acids in theliquid protein diet-A hypothesis. Obesity Bariatric Med 1979Mar-Apr; 8:49-52

172. Blackburn GL: The liquid protein controversy-A closerlook at the facts. Obesity Bariatric Med 1978 Jan-Feb; 7:25-28

173. Felig P: Four questions about protein diets. N Engl JMed 1978 May 4; 298:1025-1026

174. Bistrian BR: Clinical use of a protein-sparing modifiedfast. JAMA 1978 Nov 17; 240:2299-2302

175. Van Itallie TB: Liquid protein mayhem. JAMA 1978 Jul14; 240:144-145

THE WESTERN JOURNAL OF MEDICINE 399