What’s the relation of dietary protein to lean mass?
How does dietary protein relate to lean mass – mainly muscle – in the absence of resistance training or any other form of exercise? Can you increase muscle just through a change in diet? Some researchers decided to find out: Increased Fat-Free Body Mass and No Adverse Effects on Blood Lipid Concentrations 4 Weeks after Additional Meat Consumption in Comparison with an Exclusion of Meat in the Diet of Young Healthy Women. In this study, the researchers divided a number of young women into two groups: one with additional meat in the diet, the other with no meat at all. The study lasted four weeks. In that time, the additional meat group gained .7 kg – about 1.5 lbs. – of lean mass, and the no meat group lost about the same in lean mass.
The meat group ate an additional 270 calories a day but gained no fat. They also ate about 2.25 grams of protein per kg bodyweight, which is a large amount, well into bodybuilders’ territory. The no-meat group consumed about 1.15 g/kg protein daily. So all of the additional calories of the meat group were either burned or turned into muscle, or possibly other lean mass, such as bone.
The current opinion of exercise physiology is that about 1.8 grams of protein per kilogram of bodyweight maxes out the amount of muscle protein synthesis possible, anything above that being superfluous and burned off. The meat group in this study was well above that, but we don’t know whether they didn’t need that much, 1.8 g/kg being adequate, or whether they used all that excess protein.
Can even more protein be beneficial?
But is there any evidence that more protein than 1.8 g/kg can be beneficial? In fact there is, if one is trying to lose weight by restricting calories. In Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation, the authors state that bodybuilders getting ready for competition by restricting calories really need to up the protein content of their diet to avoid losing muscle. It appears that well over 2 g/kg a day are necessary in this particular circumstance. In this case, the higher protein didn’t put on muscle, but prevented bodybuilders who were trying to get shredded from losing muscle.
If you’re dieting to lose weight, a much higher protein intake appears to be beneficial, since it will help preserve muscle, which you do not want to lose.
The gross inadequacy of U.S. government guidelines for protein
I found one aspect of the first-linked study on young women rather ominous, and that is that on an intake of 1.15 g/kg a day of protein, they lost lean mass. Yet at the same time the RDA, Recommended Dietary Allowance, for protein is only 0.8 grams per kilogram bodyweight, or about 56 grams a day for a 70 kg man. If young women lost lean mass on a diet that provided more protein than that, obviously something is wrong. What’s wrong is the RDA for protein, which ought to be much higher. In The underappreciated role of muscle in health and disease, the author suggests that up to 1.8 g/kg bodyweight would be much healthier, as it’s been shown that the RDA cannot maintain lean mass in older people. Or probably younger, as we’ve just seen.
If you already eat a diet relatively high in protein, featuring some animal protein at each meal, you may not be able to increase lean mass much by eating more protein. On the other hand, if you follow U.S. guidelines, you should stop that, increase your protein, gain some lean mass, and become healthier, whether you are a strength athlete or not.