Before I answer that question, I want to talk about what it takes to gain 10 lb. of muscle. Most muscle gain is the result of hypertrophy (increasing the size of the muscle fibres), not hyperplasia (increasing the number of muscle fibres). So when we gain 10 lb. of muscle, we have increased the size of our existing muscle fibres, not their number.
Okay. So what might it take to actually gain 10 lb. of muscle? There are always many factors to consider but for simplicity, let’s look at an example described in a study conducted by Staron et al. (1991)1. In this study, a number of college-aged women who had previously participated in strength training agreed to follow an exercise regimen to try to gain muscle:
· They exercised twice a week for five months, focusing on leg training (since legs present good opportunity for muscle growth). They did full squats, leg presses, and leg extensions.
· On the first training day each week, they performed two warm-up sets and three sets of six reps to failure. On the second training day each week, they performed two warm-up sets and three sets of 12 reps to failure. This is very heavy training.
· Note: They were NOT trying to lose weight at the same time.
The result? After five months, the women gained an average of 5 lb. of muscle. But it was a LOT of work to gain that 5 lb., AND they were feeding themselves appropriately to see gains (just as body builders eat more in the growth phase)–not dieting. But back to the question at hand. How many more calories would they burn each day as a result of adding that 5 lb. of muscle?
To figure that out, we need to know how many calories a pound of muscle burns. In a study conducted by Wang et al. (2010)2, researchers evaluated the specific metabolic rates of the major organs, including fat and skeletal muscle. They discovered that muscle burns 14 calories per kilogram.
So let’s do the calculation together. First, we convert the pounds to kilograms:
5 lb. of muscle ¸ 2.2 (conversion factor) = 2.3 kg of muscle
Next, we multiply the kilograms of muscle by 14 to determine the number of calories burned by that amount of muscle:
2.3 kg of muscle ´ 14 calories burned per kilogram of muscle = 32 calories
So the women in the Staron et al. study would burn 32 calories more per day by adding 5 lb. of muscle. Which means that muscle burns roughly 6 calories per pound:
32 calories ¸ 5 lb. of muscle = 6 calories per pound of muscle
Now here’s the curveball. Let’s take this information and apply it to the original question: Would you burn more calories each day if you lost 50 lb. of fat and gained 10 lb. of muscle?
We’ve determined that muscle burns roughly 6 calories per pound, but to answer the question, we still need to know how many calories fat burns per pound. I will tell you! Wang et al. determined that fat burns roughly 2 calories per pound. Now we have everything we need. So:
50 lb. of fat ´ (2 calories burned per lb.) burns 100 calories per day
LOSING 50 lb. of fat ´ (2 calories burned per lb.) burns 100 FEWER calories
GAINING 10 lb. of muscle ´ (6 calories burned per lb.) burns 60 MORE calories
When we do the final math, the net balance after losing 50 lb. of fat and gaining 10 lb. of muscle is 40 fewer calories burned per day. Even though muscle burns more calories pound for pound than fat does, gaining 10 lb. of muscle (+60 calories burned per day) does not cancel out the metabolic loss that losing 50 lb. of fat creates (a net balance of 40 fewer calories burned per day).
This illustrates why it can be so difficult to keep weight off once we’ve lost it. Typically, the amount of fat we lose compared to the amount of muscle we gain leaves us with a more efficient metabolism than we started with–which means we burn fewer calories, not more. Really?!? Yes–when we lose a lot of body fat, it actually REDUCES the number of calories we burn in a day.
And this is why lifestyle approaches such as enjoying physical activity, reducing stress, identifying habits, making simple changes in your environment, etc., are more likely to lead to sustainable weight loss than just restricting what you eat.
Don’t be fooled by fad-diet advertisements that suggest you will be able to burn more calories when the diet is complete. Let real science do the talking. If you need support with weight management, let us help. We know the science and we know lifestyle!
1. Staron, R.S., et al. “Strength and skeletal muscle adaptations in heavy-resistance-trained women after detraining and retraining.” Journal of Applied Physiology, February 1991; Vol. 70, No. 2, pp 631-640.
2. Wang, Z., et al. “Specific metabolic rates of major organs and tissues across adulthood: evaluation by mechanistic model of resting energy expenditure.” The American Journal of Clinical Nutrition, December 2010; Vol. 92, No. 6, pp 1,369-77.