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Introductions

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Low Carbohydrate Diets and Weight Loss

David L. Gee, PhD

FCSN 547 - Nutrition Update

Summer 2004

The Low-Carbohydrate Diet of William Banting

• Age: 66 yrs

• Weight Loss: – 46 pounds of initial 202 pounds– over one year

• “Never hungry”

• Letter on Corpulence, Addressed to the Public. 2nd ed., London, England, Harrison and Sons; 1863.

Efficacy and Safety of Low-Carbohydrate Diets: A

Systematic Review

D. Bravata et al

JAMA 2003;289:1837-1850

Efficacy and Safety of Low-Carbohydrate Diets: A Systematic Review

• MEDLINE search for low-carbohydrate diet studies from 1966-2003– > 4 days, > 500 Cal/d, reported Cal & CHO content, relevant

outcomes

• 107 articles with 3268 participants– 663 participants consuming < 60gCHO/d– 71 participants consuming < 20gCHO/d

• No low-carb diets with participants >53 yo• Only 5 studies (non-randomized, no comparison groups)

with diet duration of > 90 days.

Efficacy and Safety of Low-Carbohydrate Diets: A Systematic Review

Findings:• Weight loss in obese subjects associated with:

– longer diet duration (p=0.002)

– restriction of calorie intake (p=0.03)

– but not carbohydrate content (p=0.90)

• Low-carbohydrate diets had no significant adverse effect on fasting serum lipids, glucose, insulin or blood pressure

• Concluded: ‘insufficient evidence to make recommendations for or against the use of low-carbohydrate diets…’

A Low-Carbohydrate, Ketogenic Diet Versus a Low-Fat Diet to Treate

Obesity and Hyperlipidemia: A Randomized, Controlled Trial.

Yancy et al.

Annals of Int. Med. 2004; 140:769-777.

Duke University

A Low-Carbohydrate, Ketogenic Diet Versus a Low-Fat Diet to Treate Obesity and Hyperlipidemia: A

Randomized, Controlled Trial.

• Setting: – Outpatient research clinic

• Participants: – 120 overweight, hyperlipidemic volunteers

• Intervention: (24 weeks)– Low CHO

• initially <20g/d, nutritional supplements, exercise recommendation, group meetings

– Low Fat• < 30% Cal from fat, < 300mg cholesterol, energy deficit of 500-

1000 Cal/d, exercise recommendation, group meetings

After 12 weeks: LC diet lost 12 kg, LF diet lost 5.5 kg

• Low CHO group had:– greater decreases in TG– increases in HDL-C– greater decreases in TG:HDL ratio

• but: 2 dropped out due to elevated LDL-C (184 to 283mg/dl @ 3mo., 182 to 219 mg/dl @ 1 mo., 30% had elevated LDL-C by >10% compared to 16% on LF diet

A Low-Carbohydrate, Ketogenic Diet Versus a Low-Fat Diet to Treate Obesity and Hyperlipidemia: A


• Other findings:• Ketonuria

– 86% positive at 2 weeks

– 42% positive at 24 weeks

• Body composition– expected fat mass lost

• LC = 9.4 kg• LF = 4.8 kg• % of total weight as fat similar in LC and LF

• Both groups blood pressure and pulse rate decreased (NS between groups)

A Low-Carbohydrate, Ketogenic Diet Versus a Low-Fat Diet to Treat Obesity and Hyperlipidemia: A

Randomized, Controlled Trial.Adverse Effects

LC Diet LF Diet PConstipation 68% 35% <0.001

Headache 60% 40% 0.03

Halitosis 38% 8% <0.001

Musclecramps

35% 7% <0.001

Diarrhea 23% 7% 0.02

GeneralWeakness

25% 8% 0.01


Randomized, Controlled Trial.Diet Composition

LC Diet LF Diet

g CHO/day 29.5 g/d (8%) 197.6 g/d (52%)

g PRO/day 97.9 g/d (26%) 70.5 g/d (19%)

g FAT/day 110.6g/d (68%) 48.9 g/d (29%)

Energy intake 1461 Cal/d 1502 Cal/d



• Conclusions

• “…a low-carbohydrate diet program had better participant retention and greater weight loss. During active weight loss, serum triglyceride levels decreased more and HDL-C increased more with the LC diet than with the LF diet.”

A Randomized Trial of a Low-Carbohydrate Diet for Obesity

G. Foster et al.

NEJM 2003;348:2082-2090

U. Penn, U. Colo, Wash U., T. Jefferson U.


• Setting– multi-center outpatient clinics

• Participants– 63 obese subjects, random controlled trial, excluded diabetics

• Intervention (1 year)– LC Diet

• RD meeting, 20gCHO/d, gradually increased, Dr. Atkins’ book, ‘self-help’

– LF Diet• RD meeting, 1200-1800 Cal/d diet, 60% CHO, 25% fat, LEARN

Program for Weight Management, ‘self-help’

A Randomized Trial of a Low-Carbohydrate Diet for ObesityAttrition Rate

LC Diet LF Diet

3 months 15% 30%

6 months 27% 40%

12 months 39% 43% (ns)


• Conclusions• “LC diet produced greater weight loss … than did

the conventional diet for the first six months, but the differences were not significant at one year.”

• “LC diet was associated with greater improvement in some risk factors for CHD.”

• “Adherence was poor and attrition high in both groups.”

The Effects of Low-Carbohydrate versus

Conventional Weight Loss Diets in Severely Obese Adults: One

Year Follow-up of a Randomized Trial

L. Stern et al.

Ann Intern Med. 2004;140:778-785

Phil. VAMC, U. Penn, Drexel U.

The Effects of Low-Carbohydrate versus Conventional Weight Loss Diets in Severely Obese Adults: One Year

Follow-up of a Randomized Trial

• Setting– outpatient clinic

• Participants– 132 adults with BMI >35, 83% with diabetes or metabolic

syndrome, RCT

• Intevention (1 year)– LC diet

• 30gCHO/day, weekly meeting for 4 weeks, monthly meetings for next 11 months

– LF diet• reduce Cal by 500 Cal/day, fat < 30%

% Cal from CHO: LC=33%, LF=50%% Cal from FAT: LC=57%, LF=34%SFA & Chol intake not different, Caloric intake in LC tended to be lower



• Summary• Weight Loss

– LC lost more weight at 6 months than LF

– after 6 months, LC maintained weight lost, LF continued to lose weight

• Serum Lipids– changes in TC and LDL-C were NS between groups

– TG decreased more in LF than LC

– HDL decreased less in LF than LC



• Summary• Glycemic Control

– no difference in glycemic control or insulin sensitivity between LC and LF

– HbA1c in diabetics was lower in LC than LF

• Diet– greater weight loss in LC may be due to lower caloric intake

– LF was not truly low fat

– SFA intake was not different in LF and LC

– MUFA intake was higher in LC than LF



• Conclusions:• “LC had more favorable overall outcomes

at 1 year than did those on LF diets”

• “Weight loss was similar, but effects on atherogenic dyslipidemia and glycemic control were still more favorable…”

Low-Carb Diets:What have we learned?

• Weight loss– LC loses more weight at 6 months but differences in weight

loss with LF disappear at 12 months– difference in weight loss may be primarily due to caloric intake

• Attrition– both LC and LF diets have high attrition rates– LF may be more due to lower rate of weight loss and ‘been

there, done that’.– LC may be more due to adverse effects and unsatisfactory

dietary restrictions.


• Health Risk Factors– TC & LDL-C not different at 1 yr

• due to weight loss difference, lack of difference in SFA intake

– HDL-C higher in LC diets• low fat diets tend to lower HDL

– TG lower in LC diets• less VLDL synthesis in LC

– small differences in glycemic control, blood pressure


• Diets– LF diets often not as low in fat as

recommended– LC diets often higher in carbs than

recommended and may contain less saturated fat than expected.

• Future

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