Intermittent FastingPrograms and Their Effectson Body Composition:Implications forWeight-Restricted SportsGrant M. Tinsley, MS, CSCS,1 Joshua G. Gann, MS,1 and Paul M. La Bounty, PhD, CSCS2

1Department of Health, Human Performance, and Recreation, Baylor University, Waco, Texas; and 2Department ofExercise and Sport Science at University of Mary Hardin-Baylor in Belton, Belton, Texas

A B S T R A C T

INTERMITTENT FASTING (IF) EN-

COMPASSES A VARIETY OF SPE-

CIFIC PROGRAMS THAT USE

SHORT-TERM FASTS TO IMPROVE

BODY COMPOSITION AND

OVERALL HEALTH THROUGH

ALTERED SUBSTRATE UTILIZA-

TION AND HORMONAL

CHANGES. THIS REVIEW EXAM-

INES THE EFFECTS OF IF PRO-

GRAMS ON BODY COMPOSITION

AND DISCUSSES POTENTIAL IM-

PLICATIONS FOR ATHLETES,

PARTICULARLY THOSE COMPET-

ING IN WEIGHT-RESTRICTED

SPORTS. INTERMITTENT FASTING

CAN REDUCE BODYWEIGHT AND

BODY FAT IN NONATHLETES, BUT

LITTLE IS KNOWN REGARDING

ATHLETIC POPULATIONS. MIXED

RESULTS REGARDING RETEN-

TION OF FAT-FREE MASS HAVE

ALSO BEEN REPORTED. A DIS-

CUSSIONOF HOW INFORMATION

FROM THE EXISTING LITERATURE

CAN BE CAUTIOUSLY USED FOR

APPLICATION IN WEIGHT-

RESTRICTED ATHLETES IS

PROVIDED.

INTRODUCTION

Athletes and active individualsoften seek to improve their bodycomposition by increasing mus-

cle mass with minimal fat gain or bydecreasing body fat while maintain-ing existing muscle mass. A combi-nation of exercise and nutritionalinterventions is typically recommen-ded to pursue these goals (12). Withinathletic populations, achieving a lowbody fat percentage is particularlyimportant for those competing inweight-restricted or “body composi-tion sensitive” sports such as mixedmartial arts, boxing, wrestling, gym-nastics, rock climbing, and figure skat-ing. For combat athletes trying to loseweight, the most common dietarystrategy is limiting daily caloric intakeso that caloric consumption is less thanthe amount needed to maintain existingbody weight (9,37). To achieve this goalof daily caloric restriction, severaldietary strategies are commonly usedby individuals in an attempt to loseweight such as eating smaller and morefrequent meals throughout the day, lim-iting carbohydrate consumption, limitingfat intake, and increasing protein intake.However, daily caloric restriction can be

difficult to maintain over long periodsof time.

In weight-restricted combat sportssuch as boxing and mixed martialarts, it is not uncommon for athletesto lose relatively large amounts ofbody weight before competition (9).After competition, significant amountsof weight are often regained becauseof the difficulty of maintaining a par-ticular dietary strategy. If this hap-pens, combat athletes may attemptto rely on more rapid, and potentiallylife-threatening, weight loss strate-gies to prepare for subsequent com-petitions. This may involve losinglarge amounts of “water weight” inthe days before their official “weigh-in” or competition, which can adverselyaffect performance and well-being(9). Thus, combat athletes in partic-ular may benefit from a dietary strat-egy that could theoretically bemaintained throughout the year andpotentially minimize large perturbations

KEY WORDS :

fasting; body composition; combat sports;weight loss; time-restricted feeding

VOLUME 37 | NUMBER 5 | OCTOBER 2015 Copyright � National Strength and Conditioning Association60

in weight between competitions. Thismay mitigate the need to lose as much“water weight” leading up to competi-tion, thereby allowing a potentially lessdifficult and safer weight cut.

Intermittent fasting (IF) is one potentialstrategy of interest to weight-restrictedathletes. IF uses regular short-term fastswith the goal of improving body com-position and overall health. AlthoughIF is a broad term that encompassesa number of specific programs, mostforms can be divided into the followingcategories: time-restricted feeding(TRF), alternate-day fasting (ADF),whole-day fasting (WDF), and Rama-dan IF. It is important to note thatmany IF programs use modified fastingrather than true fasting. True fasting re-quires abstinence from all caloric intake,but modified fasting allows smallamounts of caloric intake. Even duringmodified fasting, the total energy con-sumed is drastically lower than weightmaintenance energy needs. Modifiedfasting can be viewed as following a verylow–calorie diet but only on certaindays or parts of days.

Time-restricted feeding (e.g.,WarriorDiet (26) and Leangains method [TheLeangains Guide, Intermittent fastingdiet for fat loss, muscle gain and health.Available from: http://www.leangains.com/2010/04/leangains-guide.html])typically consists of following the sameeating pattern each day, with certainhours comprising the fasting period(12–20 hours) and the remaining hourscomprising the feeding window. Thereis variability between programs in theplacement of the fasting and feedingperiods during the day, but it is mostcommon to place the feeding periodin the evening. Alternate-day fasting al-ternates between ad libitum feedingdays (i.e., unrestricted eating) and pseu-dofasting days that allow 1 meal con-taining ;25% of daily calorie needs.Whole-day fasting (e.g., Eat Stop Eat(42)) consists of 1–2 days of fastingper week and ad libitum eating on theother days.

Ramadan IF is primarily a religious fastrather than a fasting regimen used

specifically to enhance body composi-tion and health. The effects of Rama-dan on body composition and athleticperformance have been previouslysummarized (1,13,14,47) and will notbe the focus of this review. It is impor-tant to note that both food and fluidintake are restricted during Ramadan.The potential impact of dehydrationand altered sleep schedules duringRamadan make interpretation andapplication of these studies moredifficult.

Although the majority of the researchto date has not been conducted withan athletic population, the currentbody of evidence demonstrates poten-tial benefits and concerns of IF pro-grams and sets the stage for futurestudies in athletes. The purpose of thisreview is to discuss the existingresearch in the realm of IF, particularlyeffects on body weight and composi-tion, and to discuss its potential appli-cability as an alternative dietarystrategy for athletes competing inweight-restricted sports.

METABOLIC CHANGES OFFASTING

During short-term fasting, a transitionin substrate utilization occurs, whichdecreases reliance on carbohydrateand increases reliance on fatty acids(49). Although blood glucose levelsdecline, whole body lipolysis and fatoxidation increase throughout thefirst 24 hours of food deprivation(32,44,49). The time period between18 and 24 hours of fasting has shownan;50% decrease in glucose oxidationand an ;50% increase in fat oxidation(32). It is thought that increased sym-pathetic nervous system activity, high-er concentrations of growth hormone,and reduced insulin concentrationsmay contribute to this shift in substrateutilization (36,49).

One concern associated with fasting isthat muscle will be catabolized to pro-vide substrate for gluconeogenesis. It isknown that humans adapt to pro-longed starvation by conserving bodyprotein (10,45), but increased proteol-ysis has been seen during short-term

fasting studies (21,41,43,56). However,the majority of these studies comparedmeasurements taken after an overnightfast with those taken 60+ hours later(21,41,43). Because the duration offasts during popular IF protocols ismuch shorter than 60 hours (e.g., upto 24 hours), it is possible that musclemass loss does not occur to the sameextent during shorter fasts.

Early literature examining completefasting reported that protein catabolismdid not begin to increase until the thirdday of fasting (5), and Soeters et al. (48)found that 2 weeks of ADF (alternatingbetween 20-hour fasting and 28-hourfeeding) did not alter whole-body pro-tein metabolism in lean healthy men.Although these metabolic changesare interesting, it should be noted thatthe effects of habitual short-term fastsmay be different than brief periods ofshort-term fasting in individuals whotypically follow a normal eating pat-tern. Studies that specifically examineIF protocols and track changes inbody composition are the best evi-dence regarding the effectiveness ofthese programs.

ALTERNATE-DAY FASTING

Alternate-day fasting is one of the morecommonly studied forms of IF.Alternate-day fasting consists of alter-nating between ad libitum feeding daysand modified fasting days that typicallyallow 1 meal containing ;25% of dailycalorie needs. This meal is usually con-sumed midday. Studies have consis-tently shown body weight reductionsof ;3–8% (6,16,17,24,25,28,34,58–60)and decreases in fat mass of ;4–15%(6,16,17,24,25,34,57,58,60). The majorityof studies have reported these results inobese (6,16,17,25,28,34,58,59) and over-weight subjects (18,25,59,60); however,this has been demonstrated in normalweight subjects as well (24,60). Table 1presents an overview of the methodsand results of ADF studies. Themajorityof studies used both male and femalesubjects but did not specifically examineor report sex differences.

Results regarding changes in fat-freemass have been mixed: no change was

Strength and Conditioning Journal | www.nsca-scj.com 61

Table 1Summary of ADF studies

Reference(s) Subjectsab Methodology Duration BCA

Weight and body composition (kg or %change)

BW BF FFM

Heilbronn et al. (24) 16 normalweight andoverweightM (age 346 3) and F(age 30 61)

Subjects alternated between fastingdays (no calorie intake) and adlibitum feeding days

22 d DXA 22.1 6 0.3; 22.5 60.5%

24 6 1% 53.4 to 52.8c

Johnson et al. (28) 10 obeseinactive Mand F withmoderateasthma(age NR)

All subjects alternated between fastingdays (320 kcal consumption forwomen and 380 kcal consumptionfor men by canned meal replacementshake) and ad libitum feeding days

8 wk N/A 28.5 6 1.7 (28.0 61.4%)d

NR NR

Donahoo et al. (16)—abstract

17 healthyobesesubjects(age NR)

Subjects randomized into CR and IFgroups. Subjects in the IF groupalternated between ad libitumfeeding days and fasting dayswithout food intake. Subjects in theCR group followed a 400 kcal/d deficit diet. Food was provided tosubjects in both groups

8 wk DXA IFe: 26.9 6 1.3 (27.4 61.4%); CRe: 24.7 61.3 (24.2 6 1.0%)

IFe: 23.9 6 0.7; CRe:22.8 6 0.6

IFe: 22.9 6 0.8;CRe: NC

Varady et al. (58) 16 obese Mand F (age46 6 2)

All subjects alternated between fastingdays (;25% of kcal needs asdetermined by Mifflin equation,consumed between 12 PM and 2 PM)and ad libitum feeding days

8 wk BIA 25.6 6 1.0; 25.8 61.1%

25.4 6 0.8; 45 62% to 42 6 2%

NC

Interm

ittentFastin

gandBodyCompositio

n

VOLUME37

|NUMBER

5|OCTOBER

2015

62

Table 1(continued)

Varady et al. (59) 60overweightand obeseM and F(ages: ADF:47 6 2, CR:47 6 3,exercise: 466 3,control: 466 3)

Randomized, controlled, parallel-armtrial. Four groups were used (ADF, CR,exercise [EX], and control). Subjects inADF and CR groups alternatedbetween fasting days (;25% of kcalneeds as determined by Mifflinequation, consumed between 12 PM

and 2 PM) and ad libitum feedingdays. The exercise group participatedin supervised exercise 3 times perweek on stationary bikes andelliptical machines. The sessionsprogressed from 45 min at 60%HRmax to 60 min at 75% HRmax overthe course of the study

12 wk N/A ADF: 25.2 6 1.1%; CR:25.0 6 1.4%; EX:25.1 6 0.9%;control: NC

NR NR

Varady et al. (60) 30 normalweight andoverweightM and F(ages: ADF:47 6 3,control: 486 2)

Randomized, controlled, parallel-armtrial. Two groups were used (ADF andcontrol). Subjects in the ADF groupalternated between fasting days(;25% of kcal needs as determinedby Mifflin equation, consumedbetween 12 PM and 2 PM) and adlibitum feeding days

12 wk DXA 25.2 6 0.9 (26.5 61.0%)

23.6 6 0.7 NC

Klempel et al. (34) 32 obese F(ages: ADF-HF: 42 6 3,ADF-LF: 436 2)

Subjects randomized into HF or LFgroups. Subjects in both groupsalternated between fasting days(;25% of kcal needs as determinedby Mifflin equation, consumedbetween 12 PM and 2 PM) and adlibitum feeding days

8 wk DXA HF: 24.3 6 1.0 (24.8 61.1%); LF: 23.7 6 0.7(24.2 6 0.8%)

HF: 25.4 6 1.5; LF:24.2 6 0.6

NC

Bhutani et al. (6) 64 obese Mand F(ages:combo: 456 5, ADF:42 6 2, E:42 6 2,control: 496 2)

Randomized, controlled, parallel-armfeeding trial. Four groups were used(ADF + exercise [combo], ADF,exercise [E], and control). The comboand ADF groups alternated betweenfasting days (;25% of kcal needs asdetermined by Mifflin equation,consumed between 12 PM and 2 PM)and ad libitum feeding days

12 wk BIA Combo: 26 6 4; ADF:23 6 1; E: 21 6 0

Combo: 25 6 1;ADF: 23 6 1

ADFf: 21 6 1

(continued)

Stre

ngth

andConditio

ningJo

urnal|www.nsca-scj.c

om

63

Table 1(continued)

Eshghinia andMohammadzadeh(17)

15overweightand obeseF (age 336 6)g

All subjects consumed very low caloriediets (25 to 30% of energy needs) onthe 3 weekly fasting days (Saturday,Monday, and Thursday) andconsumed a diet of 1,700 to 1,800kcal/d on feeding days

6 wk BIA 84.3 6 11.4 to 78.3 610.2

45.8 6 4.2% to 43.06 4.0%

NR

Hoddy et al. (25) 74 obese Mand F (age:ADF-L andADF-D: 456 3, ADF-SM: 46 62)

Subjects in all groups alternatedbetween fasting days (;25% of kcalneeds as determined by Mifflinequation) and ad libitum feedingdays. ADF-L consumed the fast-daymeal midday, ADF-D consumed thefast-day meal in the evening, andADF-SM divided the small mealbetween morning, midday, andevening

8 wk DXA ADF-L: 23.5 6 0.4;ADF-D: 24.1 6 0.5;ADF-SM: 24.0 6 0.5

-;3 kg in all groupsh -;1 kg in allgroupsh

ADF 5 alternate-day fasting; BCA 5 body composition assessment; BF 5 body fat; BIA 5 bioelectrical impedance; BW 5 body weight; CR 5 caloric restriction; DXA 5 dual-energy x-rayabsorptiometry; FFM 5 fat-free mass; HF 5 high-fat; HRmax 5 maximal heart rate; IF 5 intermittent fasting; LF 5 low-fat; NC 5 no change; NR 5 not reported.

aData reported as mean 6 standard error of the mean unless otherwise noted.

bWeight categories based on World Health Organization classifications based on body mass index (normal weight: 18.5–24.99, overweight: 25–29.99, obese:$30), and ages are reported inyears.

cNumerical value for SEM not provided.

dType of error reported was not specified.

eNo significant between-group changes.

fNo changes in other groups.

gMean 6 standard deviation.

hExact values not reported.

Interm

ittentFastin

gandBodyCompositio

n

VOLUME37

|NUMBER

5|OCTOBER

2015

64

reported in several studies (34,58,60),whereas others reported a decrease(6,16,24,25), and some did not reportfat-free mass changes (17,28,59). Varady(57) stated that it appears that a lowerproportion of lean mass is lost duringintermittent caloric restriction (;10%of weight loss as lean mass) comparedwith daily caloric restriction (;25%of weight loss as fat mass), but noideas concerning the potential mech-anisms behind this observation wereprovided. These percentages werebased on comparing only 3 studiesof IF with 11 studies of daily caloricrestriction. There were also differen-ces in body composition assessment(i.e., dual energy x-ray absorptiometry[DXA] versus bioelectrical imped-ance analysis [BIA]) and study design(e.g., level of caloric deficit) thatshould be considered. Without fur-ther research, it cannot be saidwhether IF leads to a lean mass-sparing effect.

WHOLE-DAY FASTING

Whole-day fasting typically consistsof 1 or 2 days of complete or modi-fied fasting each week. Whole-dayfasting studies (3,23,27,33,54,55,65)have reported reductions of ;3–9%in body weight, as well as decreasedbody fat mass. No change in leanmass was observed in 3 of the studies(23,33,55), but Teng et al. (54) re-ported a ;1% decrease after 12weeks of WDF. Two studies did notreport changes in lean mass (27,65).A limitation of these studies is thatonly one used DXA to evaluatechanges in body composition (33),whereas the remainder used BIA.Table 2 presents an overview of themethods and results of WDF studies.Contrary to ADF, most WDF studieshave examined solely male (27,54,55)or female (23,33) subjects, ratherthan a combination. However, basedon the differences between experi-mental design and subjects used(i.e., normal weight and overweightmales versus obese females), it is notpossible to determine sex differencesin the responses to these programs atthis time.

TIME-RESTRICTED FEEDING

When Ramadan IF studies areexcluded, there is very little researchexamining TRF programs. Stote et al.(50) conducted a study of TRF, whichused daily 20-hour fasts in male andfemale participants (age: 45.0 6 0.7;mean 6 SEM). The study used a ran-domized cross-over design with two8-week periods of eating either 1 mealper day or 3 meals per day. These 2phases were separated by an 11-weekwashout period, and all food was pro-vided to the subjects throughout thestudy. During the 1 meal per day phase,participants consumed all their calorieswithin a 4-hour window of time in theevening. After eating 1 meal per day, ascompared with 3 meals per day, lower-body weight (65.9 6 3.2 kg versus67.3 6 3.2 kg) and fat mass (14.2 61.0 kg versus 16.3 6 1.0 kg) were re-ported. Although both treatments weredesigned to be isocaloric, the subjectsate ;65 fewer calories per day duringthe 1 meal per day phase of the studybecause of “extreme fullness” and diffi-culty eating all the food in the allottedtime window (50). It is possible thatindividuals would have eaten even lessif they had been free to choose when tostop eating, and a lower level of energyintake could have led to even greaterweight loss. The ability to adhere tothis type of eating pattern is question-able, as indicated by higher ratings ofhunger and desire to eat in the 1 mealper day group. The severity of thesephenomena increased throughout thestudy, indicating that the subjects didnot grow adequately accustomed tothe eating pattern.

Stote et al. (50) also reported a trend(p5 0.06) for greater fat-free mass afterconsuming 1 meal per day (50.9 6 0.4kg) than after consuming 3 meals perday (49.4 6 0.4 kg). It should be notedthat body composition was assessedusing BIA, which has been previouslyquestioned in regard to fat-free massmeasurements during fasting. Faintuchet al. (18) examined nonobese individ-uals undergoing a complete fast for43 days (subjects only ingested water,vitamins, and electrolytes). During the

later stages of fasting (between the31st and 43rd day), BIA reportedunrealistic increases in fat-free mass,and the authors stated that these find-ings must be rejected because of ques-tionable plausibility. However, thefasting protocols used by Stote et al.(50) and Faintuch et al. (18) variedconsiderably. Subjects in the studyby Stote et al. (50) did not undergocomplete fasting for even 1 entireday, and the dietary changes madewere not nearly as extreme as thosein the study by Faintuch et al. (18).Taken together, these studies maydemonstrate that BIA is not the opti-mal tool for measuring lean masschanges during such fasting protocols,and the trend for greater fat-free massreported by Stote et al. (50) should beinterpreted cautiously.

No exercise intervention was used inthe study by Stote et al. (50), and nochanges in physical activity were foundthroughout the course of the study. Itshould be noted that there was a 28.6%withdrawal rate from the study, indi-cating that some individuals may notbe able to adhere to this pattern ofeating. However, there is limitedlong-term success of maintainingweight loss induced by a daily hypo-caloric diet (7,64).

INTERMITTENT FASTING ANDEXERCISE

To our knowledge, only one study hasexamined combining an IF protocolwith an exercise program (6). Thestudy examined 4 groups: ADF, ADFplus exercise, exercise alone, and con-trol. Twelve weeks of supervisedendurance exercise on stationary bikesand elliptical machines was imple-mented in the 2 exercising groups. Sub-jects exercised 3 times per week,beginning with 25 minutes at 60% oftheir age-predicted maximum heartrate (HRmax) and progressing to40 minutes at 75% HRmax over thecourse of the study. It was not reportedwhether subjects exercised onmodifiedfasting days or on ad libitum feedingdays, as well as whether subjects exer-cised in a fasted or fed state.

Strength and Conditioning Journal | www.nsca-scj.com 65

Table 2Summary of WDF studies

Reference(s) Subjectsab Methodology Duration BCA

Weight and body composition (kg or %)

BW BF FFM

Williams et al. (65) 47 obese M and Fwith type IIdiabetes (ages for3 groups were 546 7, 51 6 8, and50 6 9)

Subjects randomized to SBT or 1of the 2 VLCD groups (VLCD-1,VLCD-5). Subjects in SBTconsumed 1,500 to 1,800 kcal/d throughout the study.Subjects in VLCD-1 followeda VLCD (400 to 600 kcal/d) 1d per wk for 15 wk. Subjects inVLCD-5 followed a VLCD for 5consecutive days during weeks2, 7, 12, and 17 of the study. Onnon-VLCD days, subjectsconsumed 1,500 to 1,800 kcal/d. During the first week andlast 3 wk of the 20-wk study, allsubjects consumed a diet of1,500 to 1,800 kcal/d

20 wk N/A SBT: 25.4 6 5.9; VLCD-1: 29.6 6 5.7; VLCD-5: 210.4 6 5.4

NR NR

Harvie et al. (23) 107 overweight andobesepremenopausal F(age 40 6 4 forboth groups)

Subjects randomly assigned toIER (25% energy restriction by2 consecutive VLCD days perweek) or CER (daily 25%energy restriction). CER groupconsumed a Mediterranean-type diet (30% fat, 45% lowglycemic load carbohydrate,and 25% protein). IERconsumed ;650 kcal on VLCDdays

6 mo BIA IERcd: 26.4 (7.9 to 4.8);CERd: 25.6 (6.9 to4.4)

IERcd: 40.5% (39.0–42.0) to 37.3%(35.2–39.3); CERd:40.5% (38.7–42.3)to 38.0% (35.8–40.3)

IERcd: 47.6 (46.3–49.0) to 46.4(44.9–47.9);CERd: 49.1(47.7–50.5) to48.3 (46.7–49.9)

Teng et al. (54) 25 normal weight/overweight M(ages for 2 groupswere control: 586 6, intervention:59 6 3)

Subjects randomized intointervention (FCR) and controlgroups. Daily caloric intake inthe FCR group reduced calorieintake by 300 to 500 kcal/d andfasted for 2 nonconsecutivedays per week. The controlgroup maintained their regulareating pattern

12 wk BIA FCRe: 23.14% (71.6 66.0 to 69.3 6 6.0);CON: +1.1% (72.9 68.5 kg to 73.7 6 8.4kg)

FCRe: 26.35% (26.46 3.9 to 25.3 63.8); CON: +2.7%(25.0 6 2.9 to25.5 6 2.9)

FCRe: 20.9%;CON: +0.4%

Interm

ittentFastin

gandBodyCompositio

n

VOLUME37

|NUMBER

5|OCTOBER

2015

66

Table 2(continued)

Klempel et al. (33) 54 obese F (ageswere IFCR-L: 47 62, IFCR-L: 48 6 2)f

Subjects randomized intoprimarily liquid (IFCR-L) orprimarily food-based (IFCR-F)groups. The groups wereisocaloric and used a 30%energy restriction. Both groupsconsumed calorie restricteddiet for 6 d each wk and fastedfor 24 h (;120 kcal intake fromjuice powder)

10 wk DXA IFCR-Lfg: 23.9 6 1.4(24.1 6 1.5%); IFCR-Ff: 22.5 6 0.6 (22.66 0.4%)

IFCR-Lf: 22.8 6 1.2;IFCR-Ff: 21.9 60.7

NC

Hussin et al. (27) 32 normal weightand overweight M(ages were FCR:60 6 7, control:60 6 6)

Subjects randomized intointervention (FCR) and controlgroups. Daily caloric intake inthe FCR group reduced calorieintake by 300 to 500 kcal/d andfasted for 2 nonconsecutivedays per week. The controlgroup maintained their regulareating pattern

12 wk BIA FCR: 23.8% (74.2 6 7.8kg to 71.4 6 7.2 kg);CON: 20.9%

FCR: 25.7% (26.4 62.4% to 24.9 62.5%); CON:+1.1%

NR

Teng et al. (55) 56 normal weightand overweight M(ages—control:59 6 6,intervention: 606 5)

Subjects randomized intointervention (FCR) and controlgroups. Daily caloric intake inthe FCR group reduced calorieintake by 300 to 500 kcal/d andsubjects fasted for 2nonconsecutive days per week.The control group maintainedtheir regular eating pattern

12 wk BIA 73.1 6 7.1 to 70.6 66.7

26.4 6 3.1% to 25.16 3.1%

NC

BCA 5 body composition assessment; BF 5 body fat; BW 5 body weight; CON 5 control; F 5 female; FCR 5 fasting calorie restriction; FFM 5 fat-free mass; IFCR-F 5 intermittent fastingcalorie restriction - food based; IFCR-L5 intermittent fasting calorie restriction with liquid meals; IER5 intermittent energy restriction; M5male; NC5 no change; NR5 not reported; SBT5standard behavioral therapy; VLCD 5 very-low calorie diet.

aAll data reported as mean 6 standard deviation unless otherwise noted.

bAges reported in years.

cNo between-group differences.

dData reported as mean (95% confidence intervals).

eGroup 3 time effect.

fMean 6 SEM.

gLarger change observed in the IFCR-L group.

Stre

ngth

andConditio

ningJo

urnal|www.nsca-scj.c

om

67

The ADF plus exercise group lost moreweight and fat mass than any othergroup. The ADF and exercise alonegroups both lost weight and fat massbut did not differ in the amount lost.There were no differences betweengroups for fat-free mass changes,although the ADF did exhibit a smalldecrease in fat-free mass. Lean masswas retained in the group that exercisedand followed ADF, and the authors re-ported that the exercise program mayhave been responsible. A limitation ofthis study is that BIA was used to mea-sure body composition.

REDUCING MEAL FREQUENCY

Meal frequency is often a polarizingtopic, and many fitness practitionersrecommend a relatively high meal fre-quency. Although the number of stud-ies specifically examining different IFprotocols is limited, investigations ofmeal frequency alterations can providesome additional information about ef-fects of decreasing meal frequency.

In 1997, Bellisle et al. (4) criticallyexamined the literature to assesswhether there are benefits of increasingmeal frequency to reduce body weight.They concluded that epidemiologicalevidence for these benefits is veryweak. They also identified 2 major is-sues with observational studies of mealfrequency and weight gain: post hocchanges in meal frequency after weightgain and misreporting of energy intake(4). The post hoc changes occur whenindividuals skip meals to maintain orlose weight after weight gain hasalready occurred (4,51), generating anartificial inverse relationship betweenmeal frequency and body weight. Mis-reporting of energy intake is well docu-mented, and data from NHANES IEpidemiological Follow-Up Study pointto widespread underreporting of foodintake, particularly by those who areoverweight and reported low meal fre-quencies (4,29). In the NHANES data,reported energy intake shows an inverserelationship with body mass index andskinfold thickness that appears to beinexplicable apart from underreportingof energy intake (4).

The conclusions reached by Bellisle et al.(4) were largely echoed in 2011 throughan updated review on meal frequency byLa Bounty et al. (35) who concluded thatalthough some observational studies sup-port an inverse relationship betweenbody weight and meal frequency, themajority do not support this (in normalweight, overweight, and obese subjects).In addition to the mixed results andpotential problems with observationalstudies, it was concluded that the major-ity of the experimental studies fail tofind any consistent improvements inbody weight or body compositionthrough higher meal frequencies(8,11,19,20,22,35,50,62,66). It also ap-pears that the thermic effect of feedingis unchanged by alterations in meal fre-quency (4,31,35), although some studieshave shown increases (39,52) or de-creases (38) in response to lower mealfrequencies. More importantly, the evi-dence indicates that there is no change in24-hour energy expenditure after altera-tions inmeal frequency ranging from 2 to7 meals per day (15,22,53,61–63,66).

Recently, Schoenfeld et al. (46) con-ducted a meta-analysis evaluating exper-imental research of meal frequency as itrelates to body composition. Althoughthe initial results of the analysis seemedto favor increased meal frequency forimprovements in body composition,a sensitivity analysis revealed that a sin-gle study was responsible for this result.The authors concluded that if any ben-efits to higher or lower meal frequenciesexist, they are likely to be negligible interms of practical significance, and per-sonal choice should largely dictate theselection of a meal frequency to enhancecompliance.

It should be noted that the linebetween decreased meal frequencyand IF protocols is somewhat blurred.Intermittent fasting, by definition, isa systematic reduction in meal fre-quency. However, IF emphasizes ex-tending periods of fasting or modifiedfasting, which is not necessarily thecase when meal frequency is otherwisereduced. For example, a diet that re-duces meal frequency may includemeals at breakfast and dinner, which

leads to a significantly shorter daytimefasting window (;6–10 hours) thanmost of the IF protocols use. As dis-cussed, this prolonged fasting windowmay have beneficial effects on lipolysisand lipid oxidation, which couldpotentially lead to improved fat loss.

PRACTICAL APPLICATIONS

The lack of research specifically exam-ining the effects of implementing IFprograms in athletes makes it difficultto provide concrete recommendationsfor the use of these programs in ath-letes. However, several points are worthconsidering. Intermittent fasting can bean effective means of reducing calorieintake, body weight, and body fat innonathletes. Intermittent fasting pro-grams can be designed to allow ade-quate nutrient consumption beforeand after physical activity (i.e., exercisedoes not have to be performed ina fasted state when an IF program isimplemented). Some IF programs areas simple as abstaining from food afterdinner and not eating again until break-fast or lunch the next day. These milderTRF programs lead to a period of fast-ing that is ;12–16 hours in duration.

Most forms of IF could be modified tofit an athlete’s training schedule. InADF and WDF, the modified fastingdays consisting of very low-energyintake could be used less frequently orplaced on rest days or days with lightertraining activities. A TRF schedulecould be developed that allows the ath-lete to eat at the most critical times (e.g.,before and after training sessions andcompetition). Even using a single dayper week of modified fasting could helpan athlete achieve a negative energybalance for the week while not disturb-ing the usual pattern of food intake onheavier training and competition days.Although there is scant evidence todemonstrate the ability to adhere tothese types of dietary interventions longterm, IF may provide an alternativestrategy for athletes who are trying tolose weight or prevent weight gain.

Intermittent fasting protocols may beparticularly applicable for athletes com-peting in weight-restricted sports such

Intermittent Fasting and Body Composition

VOLUME 37 | NUMBER 5 | OCTOBER 201568

as mixed martial arts, boxing, and wres-tling. These sports often require athletesto lose significant amounts of weightbefore competition. After competition,it is not uncommon for these athletes toquickly regain the weight, creatinga “yo-yo” pattern of weight loss andweight gain—a cycle that is relativelycommon in combat sports. Intermittentfasting protocols may provide the ath-letes in these sports an alternativemethod in which they could not onlyachieve weekly caloric deficits andweight loss but also maintain adequateintake needed to provide energy forstrenuous training days.

Currently, there is a paucity of literatureon the effects of IF protocols on exerciseperformance. Thus, it cannot be deci-sively concluded if these types of dietarystrategies hinder or enhance exerciseperformance, if they affect performanceat all. However, if this type of dietarystrategy is used in a conservative fashionas described here (i.e., fasting one selectday of the week or on nontrainingdays), it could theoretically play a very-minor role in exercise performancebecause of the limited impact on mosttraining days. However, more researchand empirical data are needed to makemore definitive conclusions in this area.

It should also be noted that there aredata showing the importance of regu-larly consuming dietary protein tomaintain lean muscle tissue, which isan item of concern for many athletes(31). Thus, this should be consideredwhen using longer duration fasts.Moore et al. (40) and Areta et al. (2)have reported that ingesting 20 g ofwhey protein at regular intervals every;3 hours may be superior in regard tonet protein balance and protein synthe-sis when compared with consuming thesame total amount of protein (;80 g) inlarger, less frequent or in smaller, morefrequent doses. The benefit of eatingprotein in this quantity and frequencymay be due to the “leucine threshold”that is needed to optimize protein syn-thesis above baseline levels. Thus, if anathlete uses an IF protocol, he or shemay choose to modify it and consumewhey protein or another protein source

at metered points throughout the fast-ing window, particularly if lean masspreservation is a major concern.

Future research specifically examiningIF programs in athletes should be con-ducted, particularly in athletes compet-ing in weight-restricted sports. Thetemporal relationship between nutrientintake and athletic activities should beconsidered, and any IF program imple-mented in athletic populations shouldtake into consideration the specific re-quirements of the sport as well as indi-vidual variation and preferences.

Conflicts of Interest and Source of Funding:The authors report no conflicts of interestand no source of funding.

Grant M.

Tinsley is a doc-toral teaching/re-search assistantat BaylorUniversity.

Joshua G. Gann

is a doctoralteaching/researchassistant at Bay-lor University.

Paul M. La

Bounty is anassociate profes-sor of exercisescience at theUniversity ofMary Hardin-Baylor.

REFERENCES1. Alkandari JR, Maughan RJ, Roky R, Aziz AR,

and Karli U. The implications of Ramadan

fasting for human health and well-being.

J Sports Sci 30: S9–S19, 2012.

2. Areta JL, Burke LM, Ross ML, Camera DM,

West DWD, Broad EM, Jeacocke NA,

Moore DR, Stellingwerff T, Phillips SM,

Hawley JA, and Coffey VG. Timing and

distribution of protein ingestion during

prolonged recovery from resistance exercise

alters myofibrillar protein synthesis. J Physiol

591: 2319–2331, 2013.

3. Ash S, Reeves MM, Yeo S, Morrison G,

Carey D, and Capra S. Effect of intensive

dietetic interventions on weight and

glycaemic control in overweight men with

type II diabetes: A randomised trial. Int J

Obes 27: 797–802, 2003.

4. Bellisle F, McDevitt R, and Prentice AM.

Meal frequency and energy balance. Br J

Nutr 77(Suppl 1): S57–S70, 1997.

5. Benedict FG, Goodall HW, Ash JE,

Langfeld HS, Kendall AI, and Higgins HL. A

Study of Prolonged Fasting. Washington,

DC: Carnegie Institution, 1915.

6. Bhutani S, Klempel MC, Kroeger CM,

Trepanowski JF, and Varady KA. Alternate

day fasting and endurance exercise

combine to reduce body weight and

favorably alter plasma lipids in obese

humans. Obesity (Silver Spring) 21:

1370–1379, 2013.

7. Blomain ES, Dirhan DA, Valentino MA,

Kim GW, and Waldman SA. Mechanisms

of weight regain following weight loss.

ISRN Obes 2013: 2013. Available at:

http://www.ncbi.nlm.nih.gov/pmc/articles/

PMC3901982/. Accessed December

2014.

8. Bortz WM, Wroldsen A, Issekutz B Jr, and

Rodahl K. Weight loss and frequency of

feeding. N Engl J Med 274: 376–379,

1966.

9. Brito CJ, Roas AFCM, Brito ISS,

Marins JCB, Cordova C, and Franchini E.

Methods of body mass reduction by

combat sport athletes. Int J Sport Nutr

Exerc Metab 22: 89–97, 2012.

10. Cahill GF Jr. Starvation in man. N Engl J

Med 282: 668–675, 1970.

11. Cameron JD, Cyr MJ, and Doucet E.

Increased meal frequency does not

promote greater weight loss in subjects

who were prescribed an 8-week equi-

energetic energy-restricted diet. Br J Nutr

103: 1098–1101, 2010.

12. Centers for Disease Control and Prevention.

Healthy weight: Losing weight—DNPAO—

CDC. Available at: http://www.cdc.gov/

healthyweight/losing_weight/index.html?s_

cid5govD_dnpao_082. Accessed

December 2014.

Strength and Conditioning Journal | www.nsca-scj.com 69

13. Chaouachi A, Leiper JB, Chtourou H,

Aziz AR, and Chamari K. The effects of

Ramadan intermittent fasting on athletic

performance: Recommendations for the

maintenance of physical fitness. J Sports

Sci 30: S53–S73, 2012.

14. Chaouachi A, Leiper JB, Souissi N,

Coutts AJ, and Chamari K. Effects of

Ramadan intermittent fasting on sports

performance and training: A review. Int J

Sports Physiol Perform 4: 419–434, 2009.

15. Dallosso HM, Murgatroyd PR, and

James WP. Feeding frequency and energy

balance in adult males. Hum Nutr Clin Nutr

36C: 25–39, 1982.

16. Donahoo W, McCall K, Brannon S,

Melanson EL, and Gozansky WS. Effect of

8 weeks of intermittent fasting on weight

loss, body composition, and insulin

sensitivity in obese individuals. Obesity 17:

S258, 2009.

17. Eshghinia S and Mohammadzadeh F. The

effects of modified alternate-day fasting

diet on weight loss and CAD risk factors in

overweight and obese women. J Diabetes

Metab Disord 12: 4, 2013.

18. Faintuch J, Soriano FG, Ladeira JP,

Janiszewski M, Velasco IT, and Gama-

Rodrigues JJ. Changes in body fluid and

energy compartments during prolonged

hunger strike. Rev Hosp Clin Fac Med Sao

Paulo 55: 47–54, 2000.

19. Farshchi HR, Taylor MA, and

Macdonald IA. Decreased thermic effect of

food after an irregular compared with

a regular meal pattern in healthy lean

women. Int J Obes Relat Metab Disord 28:

653–660, 2004.

20. Finkelstein B and Fryer BA. Meal frequency

and weight reduction of young women. Am

J Clin Nutr 24: 465–468, 1971.

21. Fryburg DA, Barrett EJ, Louard RJ, and

Gelfand RA. Effect of starvation on human

muscle protein metabolism and its

response to insulin. Am J Physiol 259:

E477–E482, 1990.

22. Garrow JS, Durrant M, Blaza S, Wilkins D,

Royston P, and Sunkin S. The effect of

meal frequency and protein concentration

on the composition of the weight lost by

obese subjects. Br J Nutr 45: 5–15, 1981.

23. Harvie MN, Pegington M, Mattson MP,

Frystyk J, DillonB, EvansG,Cuzick J, JebbSA,

Martin B, Cutler RG, Son TG, Maudsley S,

Carlson OD, Egan JM, Flyvbjerg A, and

Howell A. The effects of intermittent or

continuous energy restriction on weight loss

and metabolic disease risk markers: A

randomized trial in young overweight women.

Int J Obes 35: 714–727, 2011.

24. Heilbronn LK, Smith SR, Martin CK,

Anton SD, and Ravussin E. Alternate-day

fasting in nonobese subjects: Effects on

body weight, body composition, and

energy metabolism. Am J Clin Nutr 81:

69–73, 2005.

25. Hoddy KK, Kroeger CM, Trepanowski JF,

Barnosky A, Bhutani S, and Varady KA.

Meal timing during alternate day fasting:

Impact on body weight and cardiovascular

disease risk in obese adults. Obesity

(Silver Spring) 22: 2524–2531, 2014.

26. Hofmekler O and Holtzberg D. The Warrior

Diet. St. Paul, MN: Dragon Door

Publications, 2001.

27. Hussin NM, Shahar S, Teng NIMF,

Ngah WZW, and Das SK. Efficacy of

Fasting and Calorie Restriction (FCR) on

mood and depression among ageing

men. J Nutr Health Aging 17: 674–680,

2013.

28. Johnson JB, Summer W, Cutler RG,

Martin B, Hyun D-H, Dixit VD, Pearson M,

Nassar M, Tellejohan R, Maudsley S,

Carson O, John S, Laub DR, and

Mattson MP. Alternate day calorie

restriction improves clinical findings and

reduces markers of oxidative stress and

inflammation in overweight adults with

moderate asthma. Free Radic Biol Med 42:

665–674, 2007.

29. Kant AK, Schatzkin A, Graubard BI, and

Ballard-Barbash R. Frequency of eating

occasions and weight change in the

NHANES I Epidemiologic Follow-up Study.

Int J Obes Relat Metab Disord 19:

468–474, 1995.

30. Kerksick C, Harvey T, Stout J, Campbell B,

Wilborn C, Kreider R, Kalman D,

Ziegenfuss T, Lopez H, Landis J, Ivy JL, and

Antonio J. International society of sports

nutrition position stand: Nutrient timing.

J Int Soc Sports Nutr 5: 17, 2008.

31. Kinabo JL and Durnin JV. Effect of meal

frequency on the thermic effect of food in

women. Eur J Clin Nutr 44: 389–395,

1990.

32. Klein S, Sakurai Y, Romijn JA, and

Carroll RM. Progressive alterations in lipid

and glucose metabolism during short-term

fasting in young adult men. Am J Physiol

265: E801–E806, 1993.

33. Klempel MC, Kroeger CM, Bhutani S,

Trepanowski JF, and Varady KA.

Intermittent fasting combined with calorie

restriction is effective for weight loss and

cardio-protection in obese women. Nutr J

11: 98, 2012.

34. Klempel MC, Kroeger CM, and Varady KA.

Alternate day fasting (ADF) with a high-fat

diet produces similar weight loss and

cardio-protection as ADF with a low-fat

diet. Metabolism 62: 137–143, 2013.

35. La Bounty PM, Campbell BI, Wilson J,

Galvan E, Berardi J, Kleiner SM,

Kreider RB, Stout JR, Ziegenfus T,

Spano M, Smith A, and Antonio J.

International society of sports nutrition

position stand: Meal frequency. J Int Soc

Sports Nutr 8: 4, 2011.

36. Lafontan M and Langin D. Lipolysis and

lipid mobilization in human adipose tissue.

Prog Lipid Res 48: 275–297, 2009.

37. Langan-Evans C, Close GL, and Morton JP.

Making weight in combat sports. Strength

Cond J 33: 25–39, 2011.

38. LeBlanc J, Mercier I, and Nadeau A.

Components of postprandial

thermogenesis in relation to meal

frequency in humans. Can J Physiol

Pharmacol 71: 879–883, 1993.

39. Molnar D. 36 the effect of meal

frequency on postprandial

thermogenesis in obese children.

Pediatr Res 28: 283, 1990.

40. Moore DR, Areta J, Coffey VG,

Stellingwerff T, Phillips SM, Burke LM,

Cleroux M, Godin J-P, and Hawley JA.

Daytime pattern of post-exercise protein

intake affects whole-body protein turnover

in resistance-trained males. Nutr Metab 9:

91, 2012.

41. Nair KS, Woolf PD, Welle SL, and

Matthews DE. Leucine, glucose, and

energy metabolism after 3 days of fasting in

healthy human subjects. Am J Clin Nutr 46:

557–562, 1987.

42. Pilon B. Eat Stop Eat. Ontario: Strength

Works, Inc. 2007.

43. Pozefsky T, Tancredi RG, Moxley RT,

Dupre J, and Tobin JD. Effects of brief

starvation on muscle amino acid

metabolism in nonobese man. J Clin Invest

57: 444–449, 1976.

44. Romijn JA, Godfried MH, Hommes MJ,

Endert E, and Sauerwein HP. Decreased

glucose oxidation during short-term

starvation. Metabolism 39: 525–530,

1990.

45. Saudek CD and Felig P. The metabolic

events of starvation. Am J Med 60:

117–126, 1976.

46. Schoenfeld BJ, Aragon AA, and

Krieger JW. Effects of meal frequency on

weight loss and body composition: A meta-

analysis. Nutr Rev 73: 69–82, 2015.

47. Shephard RJ. The impact of Ramadan

observance upon athletic performance.

Nutrients 4: 491–505, 2012.

Intermittent Fasting and Body Composition

VOLUME 37 | NUMBER 5 | OCTOBER 201570

48. Soeters MR, Lammers NM, Dubbelhuis PF,

Ackermans M, Jonkers-Schuitema CF,

Fliers E, Sauerwein HP, Aerts JM, and

Serlie MJ. Intermittent fasting does not

affect whole-body glucose, lipid, or protein

metabolism. Am J Clin Nutr 90:

1244–1251, 2009.

49. Soeters MR, Soeters PB,

Schooneman MG, Houten SM, and

Romijn JA. Adaptive reciprocity of lipid and

glucose metabolism in human short-term

starvation. Am J Physiol 303:

E1397–E1407, 2012.

50. Stote KS, Baer DJ, Spears K, Paul DR,

Harris GK, Rumpler WV, Strycula P,

Najjar SS, Ferrucci L, Ingram DK,

Longo DL, and Mattson MP. A controlled

trial of reduced meal frequency without

caloric restriction in healthy, normal-weight,

middle-aged adults. Am J Clin Nutr 85:

981–988, 2007.

51. Summerbell CD, Moody RC, Shanks J,

Stock MJ, and Geissler C. Relationship

between feeding pattern and body mass

index in 220 free-living people in four age

groups. Eur J Clin Nutr 50: 513–519, 1996.

52. Tai MM, Castillo P, and Pi-Sunyer FX. Meal

size and frequency: Effect on the thermic

effect of food. Am J Clin Nutr 54: 783–

787, 1991.

53. Taylor MA and Garrow JS. Compared with

nibbling, neither gorging nor a morning fast

affect short-term energy balance in obese

patients in a chamber calorimeter. Int J

Obes Relat Metab Disord 25: 519–528,

2001.

54. Teng NIMF, Shahar S, Manaf ZA, Das SK,

Taha CSC, and Ngah WZW. Efficacy of

fasting calorie restriction on quality of life

among aging men. Physiol Behav 104:

1059–1064, 2011.

55. Teng NIMF, Shahar S, Rajab NF, Manaf ZA,

Johari MH, and Ngah WZW. Improvement

of metabolic parameters in healthy older

adult men following a fasting calorie

restriction intervention. Aging Male 16:

177–183, 2013.

56. Tsalikian E, Howard C, Gerich JE, and

Haymond MW. Increased leucine flux in

short-term fasted human subjects:

Evidence for increased proteolysis. Am J

Physiol 247: E323–E327, 1984.

57. Varady KA. Intermittent versus daily calorie

restriction: Which diet regimen is more

effective for weight loss? Obes Rev 12:

e593–e601, 2011.

58. Varady KA, Bhutani S, Church EC, and

Klempel MC. Short-term modified

alternate-day fasting: A novel dietary

strategy for weight loss and

cardioprotection in obese adults. Am J Clin

Nutr 90: 1138–1143, 2009.

59. Varady KA, Bhutani S, Klempel MC, and

Kroeger CM. Comparison of effects of diet

versus exercise weight loss regimens on

LDL and HDL particle size in obese adults.

Lipids Health Dis 10: 119, 2011.

60. Varady KA, Bhutani S, Klempel MC,

Kroeger CM, Trepanowski JF, Haus JM,

Hoddy KK, and Calvo Y. Alternate day

fasting for weight loss in normal weight and

overweight subjects: A randomized

controlled trial. Nutr J 12: 146, 2013.

61. Verboeket-van de Venne WP and

Westerterp KR. Influence of the feeding

frequency on nutrient utilization in man:

Consequences for energy metabolism. Eur

J Clin Nutr 45: 161–169, 1991.

62. Verboeket-van de Venne WP and

Westerterp KR. Frequency of feeding,

weight reduction and energy metabolism.

Int J Obes Relat Metab Disord 17: 31–36,

1993.

63. Verboeket-van de Venne WP,

Westerterp KR, and Kester AD. Effect of

the pattern of food intake on human energy

metabolism. Br J Nutr 70: 103–115, 1993.

64. Wadden TA, Butryn ML, and Byrne KJ.

Efficacy of lifestyle modification for long-

term weight control. Obes Res 12(Suppl):

151S–162S, 2004.

65. Williams KV, Mullen ML, Kelley DE, and

Wing RR. The effect of short periods of

caloric restriction on weight loss and

glycemic control in type 2 diabetes.

Diabetes Care 21: 2–8, 1998.

66. Wolfram G, Kirchgessner M, Muller HL, and

Hollomey S. Thermogenesis in humans after

varying meal time frequency [in German].

Ann Nutr Metab 31: 88–97, 1987.

Strength and Conditioning Journal | www.nsca-scj.com 71