A new study adds to the body of evidence that whey protein is key for maintaining muscle during weight loss.

There’s a big difference between ‘good’ and ‘bad’ weight loss. The good kind, the kind we should all strive for, is losing the least amount of muscle in relation to body fat.

Getting enough protein is one of the keys to preventing muscle loss while dieting, but research shows protein may be lacking in a lot of weight loss diets, considering that on average the amount of weight loss most people have is about 30 percent from muscle.

A matter of hot debate has been whether the source of protein, be it animal or plant, could be an important factor in saving muscle while losing weight. Some of early research has shown, for example, that dairy proteins such as whey have been able to lead to greater fat loss while maintaining muscle.

Now a new randomised, double-blinded study has shown that whey protein supplementation can further help preserve more muscle compared to soy or carbohydrate (1). The study was published in December in the Journal of Nutrition by researchers from McMaster University in Ontario, Canada.

The 14-day weight-loss study randomised overweight or obese men and women to groups consuming prepackaged diets containing whey (27 grams), soy (26 grams), or carbohydrate (25 grams) twice daily. All of the groups lost some weight including from body fat and muscle with no significant differences.

However, the researchers found that the group that consumed whey showed greater muscle protein synthesis (MPS) compared to subjects consuming either soy or carbohydrate. Moreover, the carbohydrate group had less fat breakdown compared to the group consuming whey or soy.

In the conclusion, the study authors wrote, whey protein slowed the decline of MPS as a result of weight loss and could be an important factor in preserving muscle in long-term weight loss.

Lead researcher Stuart Phillips, Ph.D., has often noted the critical importance of maintaining muscle over time since it can play a role not only in resting metabolism, but also for supporting blood sugar control and overall mobility.

“Whey can be a useful protein because of its high content of branched-chain amino acids (namely leucine) that helps to promote muscle protein synthesis in comparison to other protein sources,” Phillips said.

The dose of whey needed to maximize muscle depends on age and amount of resistance training too.

For instance, in previous research conducted by Phillips and others, it was found that adults (20 to 65) and elderly men (65 and above) exhibited a differential response to varying amounts of whey protein after resistance training (2). For men under 65, whey protein in amounts of 20 grams at each meal was able to maximally stimulate muscle protein synthesis, whereas elderly individuals required double the dose, 35 to 40 grams, to obtain the same response.

The reason has to do with a blunted anabolic response to protein ingestion that occurs in people with age as they become more sedentary, which is why Phillips recommends getting some form of physical activity every day.

Regular resistance training of muscles in combination with obtaining quality sources of protein such as whey regularly is the key to maintaining muscle during weight loss, according to Phillips.


  1. Hector AJ, et al. Whey protein supplementation preserves postprandial myofibrillar protein synthesis during short-term energy restriction in overweight and obese adults. J Nutr. Doi: 10.3945/jn.114.200832
  2. Burd NA, et al. Greater stimulation of myofibrillar protein synthesis with ingestion of whey protein isolate v. micellar casein at rest and after resistance exercise in elderly men. Br J Nutr 1-5, 2012.