It's the body builder's holy grail: losing weight while still gaining muscle mass. Compared to that, losing weight alone is easy.

Smart athletes know that it's not even about the muscle strength or the aesthetics. Muscle increases the body's resting metabolic rate, which means that it continues to burn calories long after the workout is over. Higher muscular strength is also tied to reduced risks of cancer and cardiovascular disease.

In order to grow muscle mass, an athlete needs to develop a superior protein synthesis rate. That is, her body must synthesize more muscle that it loses. But to lose weight, it is necessary to have a calorie, or energy, deficit. This means you need to burn up more calories than you consume. However, this calorie deficit causes the body to adapt in various ways, one of which is particularly problematic in our discussion here: it creates a reduction in protein synthesis rates.

Knowing this, a typical weight loss program can seem a cruel joke. There is no clear and easy to lose the fat without also losing muscle mass. And to actually gain musculature while losing weight? Like I said, the holy grail.

Fortunately, a team of researchers at McMasters University in Hamilton, Canada, has stepped in to break it all down for us. The scientists recently concluded a month-long study, published in the the American Journal of Clinical Nutrition, in which 40 overweight men in their 20s followed a rigorous exercise program and followed a diet that consisted of 40% fewer calories than what they would normally require. The results should encourage you grail-seekers.

Half the men in the study followed a high-protein regimen (2.4 grams per kilogram of body weight) and the other half were placed on a lower, some might say “more normal” routine of protein consumption (1.2 grams per kilogram of body weight).

After 4 weeks, the higher-protein test group amassed 2.3 pounds of new muscle, and shed 10.5 pounds of fat. The lower protein crew kept their existing muscle mass and lost 8 pounds.

The University selected whey as the protein source, because it is the highest quality such source available. It contains all the essential amino acids your body needs to make protein.

Everyone in the study hit the gym 6 days a week for very closely monitored exercise. The workouts consisted of anaerobic training, like sprints and plyometrics, which traditionally burns fat in the shortest period of time. And both groups' calorie-intake was severely restricted, but otherwise identical.