A new study suggests whey protein is more effective than soy protein or carbohydrates at preserving muscle mass during a low-calorie diet.
Although consumers may embark on a weight loss diet with hopes of shedding a few pounds of fat, a common and less-desired outcome can often be the loss of muscle mass.
However, a new study1 suggests that whey protein may be more effective at preserving lean muscle mass during weight loss than soy protein or carbohydrate supplementation. Taken simultaneously with a reduced calorie diet, whey protein was found to preserve myofibrillar protein synthesis (MPS) to “a significantly greater degree than the other supplements,” according to a press release.
Losing hard-earned muscle may be every bodybuilder’s nightmare, but it can also have metabolic consequences, according to the study’s senior author, Stuart Philliips, PhD, Exercise Metabolism Research Group, McMaster University (Hamilton, Ontario).
“The greatest metabolic health benefits resulting from weight loss would be achieved with retention of muscle and a loss of fat,” said Phillips, in a press release.
The double-blind, randomized controlled trial included 40 overweight or obese participants aged 35-65. For 14 days, the participants all followed a controlled diet of pre-packaged meals based on a 750 daily calorie deficit. The participants were randomly assigned to receive twice-daily supplements of isolated whey protein, soy protein, or isoenergetic carbohydrate (maltodextrin). The supplements were figured into each participant’s daily energy allowance.
Participants were assessed before and after the weight-loss period with blood samples for plasma amino acid, insulin, glucose, and glycerol concentrations; muscle biopsies before and after meals; and body composition analyses by a DXA scan.
By the end of the 14-day trial period, all participants lost total body mass, fat mass, lean body mass, and trunk fat mass. Although MPS decreased in all groups, postprandial rates of MPS were reduced by just 9% in the whey group compared with 28% and 31% in the soy and carbohydrate groups, respectively. The researchers concluded that the reduced rate of MPS decline in the whey protein group “could translate to preserving lean body mass in longer-term weight loss.”
“Our results indicate whey would be effective at promoting the retention of muscle when people are trying to lose weight,” said Phillips.
Phillips also hypothesized that the significantly greater effect of whey protein on preserving MPS may be due to the different amino acid profiles of the supplements.
“A single amino acid from protein-known as leucine-may be the reason why certain proteins are more or less effective in stimulating MPS,” said Phillips. “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.”
1. Hector AJ et al. “Whey protein supplementation preserves postprandial myofibrillar protein synthesis during short-term energy restriction in overweight and obese adults.” Journal of Nutrition, vol. 145, no. 2 (February 2015): 246-252.
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