Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein and Carbs

[Darryl Shaw]

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

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.

http://content.nejm.org/cgi/content/full/360/9/859

[Ian Melroy]

While this is interesting, it seems like it would have been more informative with a wider range of macronutrient ratios. 10% carbs for instance or perhaps 50-60% fat. They really tested a pretty moderate range overall. It seems odd that they tested "high protein", but not "low carb".

Also, keeping a hight fat diet down to 8% saturated fat and 150mg cholesterol/1000cal seems unrealistic.

Overall though, it does make a pretty good argument for calories in - calories out reasoning as far as moderate macronutrient ratios are concerned.

-ian