The July 2010 issue of Current Opinion in Clinical Nutrition and Metabolic Care features a review of research on high protein diets and weight loss.
Co-author Donald K Layman (who will sound familiar from this post on dietary guidelines), concludes that protein intake can protect against lean muscle loss during weight loss.
He and coauthor Suzanne Devkota draw three conclusions:
1. Protein's ability to protect muscle is due, in part, to branched-chain amino acid leucine, which has been "characterized as a unique signal regulator of muscle protein synthesis."
2. When 2.5g of leucine was consumed, lean muscle was protected and fat loss was promoted.
3. Protein intake, especially as distributed throughout breakfast and lunch, can help preserve this metabolic pattern of muscle preservation and fat loss.
Earlier this year I reported on a Japanese study that found that isoleucine, another branched-chain amino acid, prevented a large percentage (45%) of fat accumulation in mice. Taken together with Layman's observations about leucine's ability to preserve muscle and promote fat loss, and you have a strong case for at least one of the mechanisms behind protein's amazing effects on body composition.
By the way, take a moment to check out the graph from the published clinical study on Aminogen and look at the increases of both leucine and isoleucine with Aminogen. The idea that adding Aminogen to whey protein enhances the building muscle/losing fat effects of protein is not new, and may be attributable to several mechanisms, including the leucine/isoleucine effects.
We know, for example, that not getting enough protein can trigger overeating, and conversely, getting healthy amounts of protein reduces your appetite, especially when compared to other macronutrients like carbohydrates and fat. Additionally, preserving your lean muscle through diet and exercise improves other measures of metabolic health like insulin sensitivity, which makes your body more efficient at handling food - and that's something we can probably all appreciate!
