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

Anthony A. Bavry, M.D., M.P.H.; Deepak L. Bhatt, M.D., F.A.C.C.




The goal of the trial was to compare the effect of different proportions of dietary macronutrients on weight loss and reduction in waist circumference.


A certain type of diet may be associated with increased weight loss.

Drugs/Procedures Used

Overweight adults were randomized to one of four diets, based on proportion of fat, protein, and carbohydrates: 1) low-fat, average-protein (n = 204); 2) low-fat, high-protein (n = 202); 3) high-fat, average-protein (n = 204); and 4) high-fat, high-protein (n = 201). Similar foods were used in all diets.

Principal Findings

Overall, 811 overweight and obese patients were randomized, and 645 (80%) completed the study. The mean age was 51 years, 64% were women, mean body mass index was 33 kg/m2, mean waist circumference was 103 cm, hypertension was present in 35%, and mean low-density lipoprotein (LDL) cholesterol was 126 mg/dl.

Among all participants over the duration of follow-up, mean weight loss was 3.6 kg for the high-protein group and 3.0 kg for the low-protein group (p = 0.22). Similarly, mean weight loss was 3.3 kg for the high-fat group and 3.3 kg for the low-fat group (p = 0.94). Among those who completed the study, the amount of weight loss was greater (mean 4 kg), although there was no difference between the diets. Most weight loss occurred in the first 6 months, and then trended up for the remainder of follow-up.

There was no change in waist circumference according to protein intake (p = 0.22), fat intake (p = 0.99), or carbohydrate intake (p = 0.39).

The decrease in LDL cholesterol over follow-up was 5.9% for the low-fat, average-protein diet; 3.9% for the low-fat, high-protein diet; 0.2% for the high-fat, average-protein diet; and 1.3% for the high-fat, high-protein diet. Satiety, satisfaction, and hunger were similar between all the diets.


Among overweight patients, a reduced calorie diet was principally important for long-term weight loss and not the proportion of fat, protein, and carbohydrates in the diet. There was similar weight loss and reduction in waist circumference with all the diets. Most weight loss occurred at 6 months and then trended up over the remainder of follow-up. LDL cholesterol was reduced the most with the low-fat, average-protein diet; however, it is unknown if this would translate into greater long-term cardiovascular benefit.

Up until now, limited data existed for recommending a certain dietary percentage of macronutrients. This randomized trial revealed that any of the four experimental diets were well tolerated, had similar satisfaction and hunger, and produced the same degree of weight loss and reduction in waist circumference.


  • Prevention


  • Diet

Study Design

Randomized. Blinded. Parallel.
Patients Screened: 1,638
Patients Enrolled: 811
Mean Follow-Up: 2 years
Mean Patient Age: 51 years
% Female: 64%

Primary Endpoints

  • Change in body weight over 2 years

Secondary Endpoints

  • Change in waist circumference over 2 years

Patient Population

  • Overweight and obese patients (body mass index 25-40 kg/m2)

  • 30-70 years of age


  • Diabetes or unstable cardiovascular disease

  • Use of weight loss medication

  • Insufficient motivation, as assessed by the interviewer


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.