There are some incredible claims out there about how valuable muscle pounds are to you. After all, we’ve been claiming for years that muscle “burns calories around the clock just to maintain itself, even while you are asleep.”
The New York Times recently published an article by Adam Zickerman, author of Power of 10: The Once-a-Week Slow Motion Fitness Revolution, “three extra pounds of lean muscle burns about 10,000 extra calories a month.”
Zickerman also says that three extra pounds of muscle “burns as many calories as running 25 miles a week, or doing 25 aerobic workouts a month without leaving your couch.” The idea is that for every pound of new muscle, your body will burn an extra 60 calories per day. Add five pounds of new muscle and you will automatically burn an additional 31 pounds of fat in a year… or so the theory goes.
When you gain muscle, your resting metabolic rate (the number of calories your body burns at rest) does go up. But, this increase is a lot less than the 50-100 calorie figure you’ll often see written.
There have been several studies tracking changes in muscle mass and metabolism. At initial glance, some of these studies appear to suggest that the metabolic rate of muscle is somewhere in the region of 50-100 calories per pound. But when you take a closer look, you’ll see that it’s not that simple.
Our Deltatrac Analysis Engine is designed to extract this information from our Boot clients. The results are consistent with several published studies, among them, an 18-week study of 26 sedentary men published in the Journal of Applied Physiology. During the first eight weeks, the men gained roughly 2.8 pounds of fat-free mass. The average daily metabolic rate increased by 263 calories per day, or 94 calories per pound. However, we can’t assume that this figure represents the metabolic rate of muscle.
First, the daily metabolic rate includes the energy cost of typical daily physical activity. We can’t presume that the increase in calorie expenditure was because of the extra muscle alone.
Second, from week 8 to week 18, the men gained another 1.8 pounds of fat-free mass. If muscle had such a big impact on metabolism, we’d expect to see another rise in the men’s metabolic rate, 169 calories per day to be exact, but this didn’t happen, nor was there any change at all in sleeping metabolic rate during the study.
In another trial published in the Journal of Clinical Endocrinology and Metabolism, women who trained with weights three days a week for six months gained 2.9 pounds of fat-free mass. In that time, resting metabolic rates increased by an average of 60 calories per day, or 20.7 calories per pound.
Unfortunately, our studies show that even this is an overestimate of the metabolic rate of all muscle.
There are other factors that cause increases in metabolism. The control group in this study did no exercise, yet their resting metabolic rate increased by 31 calories per day. One major cause that researchers are eager to test further is the impact of the nervous system on metabolism.
It’s also important to remember that fat generates metabolism as well. For years, science underestimated the workload fat tissue brings to bear on the human body. It secretes proteins that can, by themselves, affect your metabolism. According to general estimates, fat has a daily metabolic rate of two calories per pound per day, with muscle clocking in at just six calories per pound. Our findings support this fat-metabolism metric, but we can be far more specific with respect to the muscle metabolism metric. Deltatrac divides the population into eight body types. For instance, we can tell you that if you are the Body type defined in Deltatrac as Olivia, then you will likely have a muscle metabolism of 4 calories per pound. On the other hand, if you are the Body type defined in Deltatrac as Victor, then you will likely have a muscle metabolism of 16 calories per pound! That’s a huge range. Keep in mind that the Victors in our world are a rare breed while the Olivias are everywhere. When you weight the averages to account for volume differences, the broader findings are about right.
So be careful when you subject yourself to the findings of scientific studies. Even though it seems reasonable to trust the results handed down by studies that are diligent in their effort to include a cross section of all body types, it is precisely that dimension that diminishes it usefulness.