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Q: I read in some magazines that the more muscles I build the higher my resting metabolic rate, but I also read in other magazines that this increase in muscle mass does little for my metabolic rate. I’m confused. Can you clear it up?
A: Many of us have been told that building muscles can increase resting metabolic rate, which helps burn more calories while we’re simply lying around, and so armed with barbells, dumbbells and fancy machines we’ve been pumping away for every body part we can name and even those we can’t.
We feed our muscles the right proportion of carbohydrates, protein and fats, and every pound of muscle that we gain requires at least a couple of months of hard work. The average male is lucky to gain eight pounds of muscles in a year – that is, if he weight trains four or five days a week on a split program, eats six meals per day, consumes a large number of calories, supplements with adequate proteins, recovers thoroughly, and lives a relatively stress-free lifestyle conducive to building muscles. The average female, with a far lower level of the anabolic hormone testosterone as compared to that of the average male, is lucky to build even half the amount of muscles achieved by her human counterpart.
And yet we place such a holy emphasis on muscle mass as the savior of our fragile svelte from the forbidden excess. Can a few extra pounds of muscle really help fight off fat and save us from obesity? The increase in resting metabolic rate from additional muscle mass is still unquantifiable, but what’s more interesting is that there is no conclusive evidence that additional muscle mass can even raise metabolic rate. This is a fundamental area that scientists have examined for a long time – it certainly is not a novel concept – and yet no clear answer can be produced. Intuitively, though, we would think that a person with more muscles burn more calories at rest, however the relationship between muscle mass and metabolism is complicated and still not fully understood, and a claim that increasing muscle mass produces a higher resting metabolic rate is premature and likely to be wishful.
So, emerging from the clash between science and intuition, we can assume that adding muscle mass might at best burn a few more calories a day – so few that we might consider it a transient love affair with hope, rather than practicality. Because what if we bust our butts for two months to gain that pound of muscle yet decide to eat that moist caramel-drizzled chocolate cake that pairs so well with a glass of port on Saturday night? Of course, birthday celebration comes to us just once a year, but we’ll probably “celebrate” endless of other occasions throughout the year for the rest of our lives. After all, most of us just want to live a normal life, which (if we’re fortunate) often presents us the wonderful opportunities to taste the delectable foods that we were put on earth to enjoy. Should we then build a hundred pounds of muscle mass to combat the caloric intake? How much muscle can we reasonably build? How much do we want? How much is even healthy? How much muscle can even rev up our resting metabolic rate? According to the science, we will have to walk around like gorillas, if we want our resting metabolic rate to have a remote chance at burning off that chocolate cake.
Let’s look at what the research says, or doesn’t say, about exercise and metabolism.
Resting metabolic rate, the energy required to keep you alive even while you’re just lying still, accounts for approximately 60% to 75% of total daily energy expenditure. The thermic effect of feeding, the energy required to digest and absorb food, accounts for about 5% to 10%. Finally, the energy required in physical activity, the thermic effect of activity, comprises approximately 20% to 30% of daily energy expenditure.
As we can see, resting metabolic rate is the largest component in daily caloric expenditure, so that an increase in this area can result in a favorable shift in energy consumption, possibly directing weight loss.
Studies of exercising subjects indicate a short-term elevation of metabolic rate in response to a single exercise bout – generally termed the excess post-exercise oxygen consumption, or EPOC. This EPOC appears to have two phases, one lasting less than 2 hours, and the second lasting up to 48 hours. The long-held belief that chronic resistance exercise can elevate resting metabolic rate through increased muscle mass probably emerged from studies that suggest this effect; however, many other studies fail to find the same thing. Data concerning long-term effects of exercise on resting metabolic rate are potentially confounded by studies not leaving sufficient time after the last exercise bout for the termination of the EPOC – in other words, the findings of a higher metabolic rate can simply be a result of the EPOC still in effect from the last exercise session, and misinterpreted as an increase in resting metabolic rate. Additionally, many other studies suggest that the increase in metabolic rate is likely a result of an acute effect of a single bout of exercise, and less likely from chronic adaptation of exercise (Speakman, 2003; Bullough, 1995; Sale, 1995).
This should not be taken to mean that muscle mass is unimportant. Its existence is the very blessing that keeps us moving. Without it we become less physically active, which means we burn fewer calories. Its strength, power and endurance allow us to move with vitality, work with purpose, fidget with attention, and dance with grace (or not). And it can very well be that any increase in caloric expenditure outside of the gym is a reflection of us moving more as a result of our muscles becoming stronger.
Whether muscle mass can increase resting metabolic rate enough to meet the practical purpose of weight loss is still unknown, but it is a fact that exercise exerts a thermic effect that lasts for hours beyond the bout. For those of us who want to improve body composition, we should continue to move as often as we can, and with as much intensity as we’re able to, because we must remember that the thermic effect of activity comprises 20% to 30% of our daily calorie expenditure. This, therefore, is the area that we should focus on and push hard in the gym, and then sit back and enjoy the EPOC – that state of increased calorie burning – that spills over to the next 48 hours of our lives outside the gym.
To push this thermic effect of activity, we should chose exercises that are whole-body and intensive, such as squats, Deadlifts, Olympic-style lifts, sprinting and jumping. Not only do these exercises allow us to stoke the metabolic furnace, they also make us more athletic people, so that we tend to move better and with more vitality in everything we do. That is what revs up the metabolic rate!
For a list of references, or if you have questions regarding this article, please email me at Johnny@focusedtrainers.com — Johnny Nguyen
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