Training Research Update
There’s no doubting the fact that the more muscle you build the easier it is to get lean.
More Muscle = Less Fat
No, I’m not saying that everyone with a lot of muscle mass is shredded. However, if the same person gains 20 pounds of muscle, it is generally easier for them to get lean than before they built that extra muscle. For decades it was assumed that this was due to the fact that muscle burns more calories than an equivalent amount of body fat. And while that is true, the difference is not significant enough to really make a huge difference in fat loss.
While there are many reasons why more muscle means less fat, one plausible mechanisms has to do with the hormone leptin.
Leptin is a hormone released by fat cells that increases metabolic rate and decreases hunger. So you burn more calories yet consume fewer. Most people would assume that the leaner you get the more leptin you would release. Yet a recent 12-week study from Spain combining weight lifting and aerobic exercise found that as you lose body fat your leptin levels decrease. This seems counterintuitive, or at least counterproductive to continued fat loss. However, an earlier study from the same Spanish researchers shows why muscle growth is so important for continued fat loss. And it also shows why combining weight lifting with cardio is the best way to keep fat loss going as compared to cardio alone.
The Spanish researchers reported that in the dominant arm of male pro tennis players, which had 15% more muscle mass than the opposite arm, they also had higher levels of leptin receptors.
Having more leptin receptors means that bigger muscles would have a higher sensitivity to leptin. This means that you likely would get a bigger spike in metabolic rate despite having lower levels of leptin. And this may be one of the reasons why building bigger muscles can make getting leaner all the easier. It also highlights the fact that the best way to lose body fat and to continue losing body fat over the long term is with a program that combines weight training and cardio. I can’t tell you how many times people contact me and ask, “If I want to focus on fat loss should I just do cardio and then lift weights after I lose the fat, or is it OK to also lift weights while trying to lose fat?” My answer is of course that you definitely want to do both for the best fat loss. And this research shows one reason why lifting weights and doing cardio is superior for fat loss than just doing cardio alone. Since cardio doesn’t build muscle, but will decrease body fat, it may lower leptin levels, but without an increase in muscle size, may not increase leptin sensitivity enough to offset the lower leptin levels.
Olmedillas, H., et al. Training, leptin receptors and SOCS3 in human muscle. Int J Sports Med. 32(5):319-26.
Olmedillas, H., et al. Muscle hypertrophy and increased expression of leptin receptors in the musculus triceps brachii of the dominant arm in professional tennis players. Eur J Appl Physiol. 2010 Mar;108(4):749-58.