A recent study published in the New England Journal of Medicine examined how different percentages of fat, protein and carbohydrate affect weight loss in individuals consuming the same numbers of calories. In the study, 811 overweight adults were randomly assigned to one of four diets: high fat and high protein, high fat and average protein, low fat and high protein, or low fat and average protein. Each diet totaled at least 1,200 calories and fell within the guidelines for cardiovascular health. The dieters were encouraged to exercise at least 90 minutes a day, in addition to being offered individual counseling every eight weeks and group counseling several times a month.
After six months, the participants had lost about 13 pounds, which amounted to 7% of total body weight. However, they began to regain slowly after about 12 months, which suggests that the participants found it difficult to restrict themselves to the prescribed regimen. After two years, 80% of the participants were able to complete the study and researchers found no significant difference in weight loss among the four different groups. Participants maintained an average weight loss of 8.8 pounds.
Researchers concluded that the calorie reduction was the most important factor in successful weight loss, with the proportions of fat and protein playing a less important role. A particularly interesting outcome of the study was that participants who missed fewer counseling sessions had better results, suggesting that social support is a key component to a healthy diet.