Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates.
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.)
Sacks
Frank M
FM
Department of Nutrition, Harvard School of Public Health, Boston, USA.
Bray
George A
GA
Carey
Vincent J
VJ
Smith
Steven R
SR
Ryan
Donna H
DH
Anton
Stephen D
SD
McManus
Katherine
K
Champagne
Catherine M
CM
Bishop
Louise M
LM
Laranjo
Nancy
N
Leboff
Meryl S
MS
Rood
Jennifer C
JC
de Jonge
Lilian
L
Greenway
Frank L
FL
Loria
Catherine M
CM
Obarzanek
Eva
E
Williamson
Donald A
DA
D001794:Blood Pressure; D001835:Body Weight; D002318:Cardiovascular Diseases; D002784:Cholesterol / Q000097:blood; D003376:Counseling; D003920:Diabetes Mellitus; D050528:Diet, Carbohydrate-Restricted; D018752:Diet, Fat-Restricted; D004038:Diet, Reducing / Q000379:methods*; D004041:Dietary Fats / Q000008:administration & dosage; D002149:Energy Intake; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000178:diet therapy* / Q000503:physiopathology / Q000628:therapy; D010349:Patient Compliance; D012307:Risk Factors; D012527:Satiation; D055105:Waist Circumference; D015431:Weight Loss
D004041:Dietary Fats; D002784:Cholesterol