Comparison of Weight-Loss Diets With Different Compositions of Fat, Protein, and Carbohydrates

N Engl J Med. 2009 Feb 26;360(9):859-73. doi: 10.1056/NEJMoa0804748.

Abstract

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.)

Publication types

  • Comparative Study
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Blood Pressure
  • Body Weight
  • Cardiovascular Diseases
  • Cholesterol / blood
  • Counseling
  • Diabetes Mellitus
  • Diet, Carbohydrate-Restricted*
  • Diet, Fat-Restricted*
  • Diet, Reducing / methods*
  • Dietary Fats / administration & dosage
  • Energy Intake
  • Female
  • Humans
  • Male
  • Middle Aged
  • Obesity / diet therapy*
  • Obesity / physiopathology
  • Obesity / therapy
  • Patient Compliance
  • Risk Factors
  • Satiation
  • Waist Circumference
  • Weight Loss*

Substances

  • Dietary Fats
  • Cholesterol

Associated data

  • ClinicalTrials.gov/NCT00072995