Although scientists routinely debate how much protein we need to eat to optimize our muscle and strength gains, they don’t disagree on another point about athletes and protein. When you reduce total calories, carbohydrates, or both, it’s essential that you also increase your protein. Not doing that puts muscle in danger of being used for energy.
In practice, most athletes are well aware that they need to eat more protein while dieting. As usual, it takes a little time for science to catch up to long-standing athletic and bodybuilding practice.
An example is a new study that had 20 young, healthy weight-trained athletes as subjects. For the second week of the study the athletes ate 100 percent of their usual total calories while getting 15 percent of those calories as protein. For the next two weeks they got 60 percent of their normal calorie intake but with different protein allocations. One group continued to get 15 percent of total calories as protein, while the other group got 35 percent as protein. Specifically, the lower-protein group got one gram of protein per kilogram of bodyweight, while the high-protein group got 2.3 grams per kilogram of bodyweight. Thus, a 200-pound bodybuilder in the high-protein group would get 207 grams of protein daily, while one in the low-protein group would get only 90 grams. All the subjects used their normal training routines throughout the one-month study. Each week they also underwent tests to measure physical performance and blood levels of various hormones, glucose and fatty acids.
At the end of four weeks those on the lower-protein diet had significantly greater losses of lean mass, or muscle, than those in the higher-protein group, while there were no differences in measures of fat loss or performance. The high-protein subjects did have more urea in their bodies, which makes sense, as urea is the major nitrogen waste product of protein metabolism. Those in the higher-protein group also reported greater feelings of fatigue.
Most studies that examine higher-protein diets involve obese, out-of-shape subjects, but this one differed because the subjects were fit athletes. Surprisingly, data concerning athletes following high-protein diets are sparse. One study showed higher nitrogen retention by those who ate more protein while dieting. More recent studies have shown no effects of increased protein in helping to preserve muscle during a diet. Another showed that taking branched-chain amino acids didn’t help preserve muscle either. That latter result is particularly curious, as most scientists believe that one of the BCAAs, leucine, powerfully protects muscle under dieting conditions. There’s more than meets the eye in those negative findings, however.
For example, the study that found no protective effects when subjects got more protein while dieting used soy as the extra protein, and soy is known to increase protein breakdown. In addition, soy appears to be used more by internal organs than by muscle. In the new study described here, the protein all came from higher-quality animal sources, such as dairy, fish, chicken and meat, which contain more favorable patterns of amino acids than soy.
As for the study that found that BCAAs failed to protect muscle during a diet, it did not take into account that BCAAs alone can’t do that. You need to supply all the essential amino acids through complete-protein foods like the ones cited above. Taking BCAAs only at the expense of other essential aminos can create an amino acid imbalance and is unlikely to preserve muscle when you diet.
A high-protein diet can help maintain muscle in several ways. For one thing, it helps maintain anabolic hormones, such as insulin, testosterone and insulinlike growth factor 1. For another, the increased amino acids you get with the added protein tend to blunt the catabolic activity of the hormone cortisol. A higher-protein diet will also blunt the activity of myostatin, a protein that blocks muscle growth and that works with cortisol to degrade muscle tissue.
In previous studies a short-term calorie reduction didn’t seem to hurt performance. Similar findings have occurred in studies where carbohydrate intake was reduced in bodybuilders and other athletes.
The one negative effect that showed up in the higher-protein group involved the subjects’ feelings of fatigue. While the authors say that there is no explanation for it, especially as none of the tests showed any drops in performance, the study did involve a drop in total calories of 40 percent in one week. I’d say that kind of drop in fuel is bound to result in feelings of fatigue in most people.
The authors also suggest that protein intake should be calibrated to total calories, and the fact that the added protein did preserve muscle under such extreme conditions proves that getting more protein is an essential strategy if you want to keep your muscle when you’re on a diet. On the other hand, when you’re not on a diet, the authors suggest, one gram of protein per kilogram of bodyweight is sufficient.