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18.12.2009

Dieting bodybuilders retain muscle with high protein foods

When you reduce your daily energy intake to 60 percent of what you burn, you don't necessarily have to lose muscle mass. If you increase your protein intake your muscles will stay as they are, write sports scientists from the University of Birmingham in England in an article that will appear soon in Medicine & Science in Sports & Exercise.

If we disregard the experience of tens of thousands of athletes for a moment, and just look at the scientific literature, we don't know much at all about weight loss in power athletes on a high protein diet. Most of the studies that have been done have involved overweight people. They not only lose more kilograms on a protein-rich diet, they also retain more kilograms of muscle mass. Do strength athletes also react as well to a protein-rich weight loss diet? This was the question to which the researchers sought an answer.

Study
The Brits put 20 bodybuilders aged between 18 and 40 on a two-week long strict diet. The athletes consumed 40 percent less energy than they burned each day. Before going on the diet the athletes' diet consisted of 15 percent protein. Per kilogram bodyweight they consumed about 1.6 g protein per day.

One group of bodybuilders just reduced what they ate. As a result, their protein intake fell to 1 g protein/kg/day. The other group not only ate less, but replaced fats and carbohydrates with protein. Their diet therefore consisted of 35 percent protein and their daily protein intake rose to 2.3 g/kg. The test subjects got their extra protein from shakes.

Results
The figure below shows that the raised protein intake almost completely blocked muscle mass breakdown. The high-protein group only lost body fat.

The protein diet had no effect on the subjects' 1RM on the bench presses. The test subjects on the protein diet managed a few more reps at 60 percent of the weight at which they could still just manage one more rep.

Explanation
The researchers think that the amino acids in proteins have a direct anabolic effect on the muscles, and that this is the main way a protein-rich diet helps retain muscle tissue. What a protein-rich diet also does is maintain levels of anabolic hormones. In the bodybuilders who just reduced their intake, the level of free testosterone fell by 26 percent. In the bodybuilders who lost weight on a protein-diet, testosterone only decreased by 7 percent.

Conclusion
"The practical implication of these results is that the protein content of a hypoenergetic diet may play a crucial role", the Brits conclude. "Athletes aiming for body weight reduction while maintaining lean body mass may be advised to keep protein intake high."

Source:
Med Sci Sports Exerc. 2009 Nov 13. [Epub ahead of print].

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