Published in the Journal of Nutrition, the study looked at how the consumption of different sources of proteins – soy or whey – during a 14-day hypoenergetic diet of 2750 kcal per day affected protein synthesis in the rod-like structures called the myofibrillar and lipolysis, the process whereby the body breaks down fat.
The researchers gave 40 overweight or obese volunteers aged 35-65 years with a body mass index of 28–50 kg/m2 twice-daily supplements of either isolated whey (27 g/supplement) or soy (26 g/supplement) or isoenergetic carbohydrate (25 g maltodextrin/supplement).
“The novel finding from this study was that twice-daily consumption of whey protein resulted in an attenuation of the postprandial decline in MPS [myofibrillar protein synthesis] during a short-term dietary hypoenergetic diet vs. twice-daily supplementation with soy protein or carbohydrate," the researchers from the McMaster University in Canada and University of Birmingham in the UK wrote.
Lipolysis was suppressed in all groups, but to a greater extent for those given the carbohydrate.
Professor Stuart Phillips, one of the McMaster University researchers behind the study, told NutraIngredients: “Including whey protein as part of a weight loss regimen can result in a reduced rate of the decline normally seen in muscle protein synthesis during an energy deficit. This could translate to preserving lean body mass in longer-term weight loss.”
Last year meta-analysis of 14 trials found whey protein as a supplement or in combination with resistance exercise, or as part of a weight-loss or weight-maintenance diet, may boost body composition for men and women
He said the results highlighted the importance of “high quality weight loss”, whereby loss of weight during low-calorie diets equated to the lowest possible ratio of lean body mass to fat mass.
This distinguished exactly what was being lost when dieting. This could be excess fat mass, particularly visceral adipose tissue, which contributes to inflammation in obesity and is linked to a greater risk of cardiovascular disease and type 2 diabetes.
However, it could also mean a loss of lean body mass, a large component of which is muscle mass and is a major contributor to the body’s resting energy expenditure, mobility and use of glucose.
“Our research team proposes that weight loss plans should aim to maximise retention of lean body mass and reduction of fat mass in order to achieve the greatest metabolic benefits.”
He said the research added to the body of evidence that suggested that the proportion of dietary protein as energy during weight loss should be increased in order to positively affect body composition by retaining muscle mass while losing fat. However it also shed light on the importance of the source of that protein.
Source: The Journal of Nutrition
Published online ahead of print, doi:10.3945/jn.114.200832
“Whey Protein Supplementation Preserves Postprandial Myofibrillar Protein Synthesis during Short-Term Energy Restriction in Overweight and Obese Adults”
Authors: A. J. Hector, G. R. Marcotte, T. A. Churchward-Venne, C. H. Murphy, L. Breen, M. von Allmen, S. K. Baker and S. M. Phillips