A recent study published in the American Journal of Clinical Nutrition by a group from the University of Maastricht in the Netherlands discusses an interesting concept called the Protein Leverage Hypothesis, which suggests that the body more closely regulates protein intake than total energy intake. If this is so, it may explain why high protein diets seem to be more effective in promoting weight loss than diets that call for an across-the-board decrease in all of the energy nutrients (carbohydrate; fat; and protein).
To-date, this concept has been extensively tested in various animal models, but not a lot of human data exist to support or refute the hypothesis. In short, the researchers in this study provided diets consisting of 5%, 15% or 30% calories from protein to 40 human subjects over a 12 day period. The added protein in the higher protein groups was swapped at the expense of dietary carbohydrate, so that all of the diets contained an equal amount of calories.
The researchers found that the subjects consumed less when the percentage of protein in the diet was greatest, suggesting that protein intake is regulated at a more constant level than that of carbohydrate or fat. This may have something to do with the satiating effects of protein, though other factors may be at play as well. In any case, these results are at least suggestive of the idea that a higher protein diet may aid in weight loss and obesity prevention. Although the subjects in the present study did not lose a significant amount of weight with one diet versus another, the relatively short time period of the study may have had something to do with that.
There is no doubt that longer term research of this nature is required to support or refute the Protein Leverage Hypothesis. Nevertheless, the results of this study provide food-for-thought that a higher protein diet has advantages over a higher carbohydrate/fat diet with respect to weight maintenance and weight loss.