Researchers at the Harvard School of Public Health and Pennington Biomedical Research Center of the Louisiana State University System did a comparison of overweight participants assigned to four different diets over a two-year period showed that reducing calories achieved weight loss regardless of which of the three nutrients was emphasized.
Low-fat, average protein: 20 percent of calories from fat, 15 percent of calories from protein, 65 percent of calories from carbohydrate.
- Low-fat, high-protein: 20 percent fat, 25 percent protein, 55 percent carbohydrate.
- High-fat, average protein: 40 percent fat, 15 percent protein, 45 percent carbohydrate.
- High-fat, high-protein: 40 percent fat, 25 percent protein, 35 percent carbohydrate.
Each participant received a diet prescription that encouraged a 750-calorie reduction per day. However, none ate less than 1,200 total calories per day. Participants were asked to do 90 minutes of moderate exercise each week.
The main finding was that diets with varying emphases on carbohydrate, fat and protein levels all achieved clinically meaningful weight loss and maintenance of weight loss over a two-year period.