New research published in the February 2015 issue of the Journal of Nutrition shows twice-daily whey protein supplementation, as part of an energy-restricted diet, is better than soy protein or carbohydrate supplementation at preserving muscle protein synthesis (MPS) during weight loss in obese and overweight adults. 

The double-blind, randomized controlled trial included 40 overweight or obese participants who received supplements of whey protein, soy protein or carbohydrate as part of their reduced calorie diet. While it is normal to see a decline in MPS during a time of caloric restriction, the whey protein supplement preserved protein synthesis to a significantly greater degree than the other supplements. Specifically, MPS rate was only reduced by 9 percent in the whey group, in sharp contrast to a reduction of 28 percent seen in the soy supplement group and the 31 percent reduction in the carbohydrate supplement group.

Whey supplementation also led to significantly higher levels in plasma amino acid concentrations, including the branched-chain amino acid leucine, which has been shown to be a potent stimulator of muscle protein synthesis. “The greatest metabolic health benefits resulting from weight loss would be achieved with retention of muscle and a loss of fat,” said Stuart Phillips, PhD, FACSM, FACNii the study’s senior author. “Although higher protein diets have been shown to promote retention of muscle during weight loss, many protein sources are known to affect MPS differently. A single amino acid from protein—known as leucine—may be the reason why certain proteins are more or less effective in stimulating MPS. In our study, we showed that whey, but not soy, protein preserved the MPS response during weight loss. These results may not be surprising when one considers whey has more leucine than soy. Our results indicate whey would be effective at promoting the retention of muscle when people are trying to lose weight.”

Whey protein is a high-quality, complete protein naturally found in dairy. This means it is readily digested and absorbed by the body and contains all of the essential amino acids (protein “building blocks”) the body needs. Whey protein also is one of the best sources of the branched-chain amino acid leucine. Existing evidence at the cellular level (at least in adipocytes and muscle cells) suggest leucine — in addition to muscle synthesis stimulating properties — also may have a synergistic role in muscle and adipocyte cells because it inhibits adipocyte lipogenesis and stimulates lipolysis.iii,iv More data, however, is needed to confirm this in humans.

This research is one of several studies supported by the Whey Protein Research Consortium, an international partnership working together to support whey research. Other studies from the Consortium have shown that daily consumption of whey protein resulted in positive anthropometric changes compared to carbohydrates in free-living overweight and obese adultsv and that whey protein, either as a supplement combined with resistance exercise or as part of a weight-loss/weight-maintenance diet, may provide body composition benefits to both men and women.vi

“The Consortium’s work supports evidence-based scientific research into the muscle benefits of whey protein,” said Moises Torres-Gonzalez, PhD, a dairy proteins subject matter expert at the Whey Protein Research Consortium.vii “We continue to learn more about the value of whey protein as part of a diet or as a supplement in consumers experiencing different health conditions and across various ages and life stages. The growing body of validated science showcases the vital impact whey protein could have on muscle health.”

The study can be accessed here...