The role of protein in weight management.

Several studies have shown that high protein meals and foods are more satiating than high carbohydrate or high fat meals when assessed by subjective ratings of satiety. Few of these studies were able to control for potentially confounding variables. Test meals differ widely in physical and sensory properties so it cannot be concluded that it is protein conferring these effects. When sensory properties are controlled up to 10-30% more calories are eaten at a subsequent meal with a high carbohydrate liquid meal than a high protein liquid meal with no difference in protein sources or BMI status. Weight loss studies examining the metabolic effects of isocaloric high protein energy restricted diets with high carbohydrate structured diets have not shown differences in kilojoule intake and weight loss despite expected satiety differences. Such studies do not allow the effects of increased satiety attributable to protein to be expressed as the dietary protocols have required all foods to be consumed. However, several longer term studies have noted improvements in body composition on a higher protein pattern despite similar weight loss. An interaction between protein intake and exercise on improved lean mass retention has also been observed. Studies comparing ad libitun high protein diets to high carbohydrate diets have usually shown greater weight loss on the high protein pattern and that enhanced satiety was the most important factor in the weight loss.