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Background The possible advantage for weight loss of a diet that emphasizes protein, fat, or carbohydrates has not been established, and there are few studies that extend beyond 1 year.
Methods We randomly assigned 811 overweight adults to one of four diets; the targeted percentages of energy derived from fat, protein, and carbohydrates in the four diets were 20, 15, and 65%; 20, 25, and 55%; 40, 15, and 45%; and 40, 25, and 35%. The diets consisted of similar foods and met guidelines for cardiovascular health. The participants were offered group and individual instructional sessions for 2 years. The primary outcome was the change in body weight after 2 years in two-by-two factorial comparisons of low fat versus high fat and average protein versus high protein and in the comparison of highest and lowest carbohydrate content.
Results At 6 months, participants assigned to each diet had lost an average of 6 kg, which represented 7% of their initial weight; they began to regain weight after 12 months. By 2 years, weight loss remained similar in those who were assigned to a diet with 15% protein and those assigned to a diet with 25% protein (3.0 and 3.6 kg, respectively); in those assigned to a diet with 20% fat and those assigned to a diet with 40% fat (3.3 kg for both groups); and in those assigned to a diet with 65% carbohydrates and those assigned to a diet with 35% carbohydrates (2.9 and 3.4 kg, respectively) (P>0.20 for all comparisons). Among the 80% of participants who completed the trial, the average weight loss was 4 kg; 14 to 15% of the participants had a reduction of at least 10% of their initial body weight. Satiety, hunger, satisfaction with the diet, and attendance at group sessions were similar for all diets; attendance was strongly associated with weight loss (0.2 kg per session attended). The diets improved lipid-related risk factors and fasting insulin levels.
Conclusions Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize. (ClinicalTrials.gov number, NCT00072995
[ClinicalTrials.gov]
.)
Source Information
From the Department of Nutrition, Harvard School of Public Health (F.M.S., L.M.B.); the Channing Laboratory (F.M.S., V.J.C., N.L.) and the Endocrine Division (M.S.L.), Department of Medicine, Brigham and Women's Hospital and Harvard Medical School; and the Department of Nutrition, Brigham and Women's Hospital (K.M.) — all in Boston; Pennington Biomedical Research Center of the Louisiana State University System, Baton Rouge (G.A.B., S.R.S., D.H.R., S.D.A., C.M.C., J.C.R., L.J., F.L.G., D.A.W.); and the National Heart, Lung, and Blood Institute, Bethesda, MD (C.M.L., E.O.).
Related Letters:
Comparison of Weight-Loss Diets
Boling C. L., Westman E. C., Yancy W. S., Sacks F. M., Bray G. A., Loria C.
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N Engl J Med 2009;
360:2247-2248, May 21, 2009.
Correspondence
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