More Muscle Means A Faster Metabolism
Many experts assume that the our metabolism – the chemical reactions that happen in living organisms to maintain life – increases very little from resistance training. Some fitness experts argue that building more muscle increases it as little as 1-5 calories per pound of muscle built.
While this seems to be a reasonable estimate for each pound of muscle you have, these experts neglect to consider the totality of the trained muscle and how this affects metabolic rate. Research indicates that resistance exercise or weight lifting gives your metabolic rate a serious boost – a lot more than just a few calories for the added muscle.
Dr. Wayne Westcott, an icon in the fitness industry and a good friend, has written an excellent article explaining how what and why this is. I hope this article will encourage you all to hit the weight room twice weekly.
Here you go:
In his book LifeFit, America’s leading epidemiologist, Ralph Paffenbarger, M.D., makes the following statement regarding the effects of muscle gain and metabolic change: “Indeed, when you replace 10 pounds of fat with 10 pounds of muscle, your weight remains the same, but you can expect to expend 500 or more additional kilocalories each day at rest.”3 In other words, Paffenbarger ascribes the resting metabolic requirement for 1 pound of muscle at 50 calories per day.
In her book Ultimate Fitness, author Gina Kolata quotes world-renowned exercise physiologist Claude Bouchard as saying, “Skeletal muscle burns about 13 calories per kilogram of body weight over 24 hours when a person is at rest.2” In other words, Bouchard ascribes the resting metabolic requirement for 1 pound of muscle at less than 6 calories per day.
He supports his opinion by saying that a man who weighs about 155 pounds has about 62 pounds of skeletal muscle, which accounts for approximately 22% of his resting metabolism (1,600 calories resting metabolism x 22% used by muscles = 352 calories used by muscles ÷ 62 pounds of muscle = 5.7 calories per pound by muscle per day at rest).
By simply adding as little as 3 lbs. of “trained muscle,” one can burn an additional 115 calories a day while at rest. Bouchard therefore states that, “Weight lifting has virtually no effect on resting metabolism.”
Revisiting The Classic Research
Although Bouchard’s mathematical calculations seem to make sense, they definitely do not line up with the classic research studies on this topic. In 1994, two well-conceived and well-conducted research studies examined the effects of strength training on muscle development and resting metabolic rate.
One study was conducted by Campbell and his research associates at Tufts University1,and the other study was conducted by Pratley and his research associates at the University of Maryland5.
At Tufts University, the subjects performed progressive resistance exercise three days a week for 12 weeks. Each training session consisted of four standard strength exercises, each of which was performed for three sets of eight to 12 repetitions.
After three months of training, the subjects, on average, added 3.1 pounds of lean (muscle) weight and lost 4.0 pounds of fat weight. As a result, their resting metabolic rate increased by 6.8 %, or approximately 105 calories per day. At face value, this finding would indicate that 1 pound of muscle uses about 35 calories per day at rest (105 calories per day ÷ 3 pounds of muscle = 35 calories per day per pound of muscle).
At the University of Maryland, the subjects performed progressive resistance exercise three days a week for 16 weeks. Each training session consisted of 14 standard strength exercises, most of which were performed for one set of 10 to 15 repetitions.
After four months of training, the subjects, on average, added 3.5 pounds of lean (muscle) weight and lost 4.2 pounds of fat weight. As a result, their resting metabolic rate increased by 7.7%, or approximately 120 calories per day. At face value, this finding would indicate that 1 pound of muscle uses about 34 calories per day at rest (120 calories per day ÷ 3.5 pounds of muscle = 34 calories per day per pound of muscle).
It is interesting to note that, in both of these studies, the same strength-training program that increased lean (muscle) weight by about 3 pounds, likewise increased resting metabolic rate by about 7%.
It is also interesting to note that, in both of these studies, the strength-training programs responsible for these impressive results were relatively basic and brief. The Tufts University subjects performed just 12 sets of exercise per session (three sets of four exercises), and the University of Maryland subjects completed 17 sets of exercise per session (one set of 11 exercises and two sets of three exercises).
These represent essentially 30-minute workouts that are manageable both time-wise and energy-wise for most adults. It is nothing short of remarkable that such modest investments in strength exercise can produce such profound physical outcomes.
Although a few studies on this topic have not noted increases in muscle mass and resting metabolic rate as a result of strength training, these have involved relatively large reductions in caloric intake.
When calories are significantly restricted, the body assumes a starvation/survival mode, and does not respond in the same manner as when the appropriate amount of calories are consumed. Essentially, all studies that do not involve low-calorie diets show significant increases in muscle mass and resting metabolic rate after 10 weeks or more of sensible strength training.
Added Muscle Vs. Trained Muscle
At face value, the results of these studies indicate that 1 pound of new muscle uses about 35 calories a day at rest. However, this is undoubtedly a high estimate, since it assumes that the only training-induced change is the addition of new muscle tissue, which is entirely responsible for the metabolic increase. I submit that all of the skeletal muscle affected by the strength-training program experiences an increase in protein turnover.
In other words, I suggest that all of the trained muscle tissue has a higher resting metabolic rate than it had prior to the exercise program. Of course, I can’t state how many additional calories each pound of trained skeletal muscle uses, but it may be on the order of 1.5 calories per pound of muscle tissue. Let’s go back to Bouchard’s example and do some calculations to see if this makes sense.
If a 155-pound man with a resting metabolic rate of 1,600 calories per day has approximately 62 pounds of skeletal muscle, and each pound uses 5.7 calories per day at rest, then the contribution to his resting metabolism is about 353 calories (62 pounds of muscle x 5.7 calories per pound = 353 calories).
However, if the strength-training program adds 3 pounds of muscle tissue for a total of 65 pounds of skeletal muscle, and if each pound of trained muscle now uses 7.2 calories per day at rest (a 1.5 calorie increase), then the new contribution to his resting metabolism is about 468 calories (65 pounds of muscle x 7.2 calories per pound = 468 calories).
This represents about 115 additional calories expended each day at rest (353 calories to 468 calories = 115 calories), which increases his resting metabolic rate by approximately 7 % (1,600 calories per day x 7 % = 112 more calories). This metabolic increase is consistent with the research findings by both Campbell, et al., and Pratley, et al.
Comparisons of Research Studies:
Campbell, et al. Tufts University
4 exercises, 3 sets
3 times per week 12 weeks
Change in lean mass +3.1 lbs.
Change in RMR +6.8%
Pratley, et al. University of Maryland
14 exercises, 1 set/2 sets;
3 times per week for 16 weeks
Chane in lean mass +3.5 lbs.
Change in RMR +7.7%
I am, therefore, suggesting that a standard three-month strength-training program may produce the following effects in previously sedentary adults:
*Increase lean (muscle) weight by about 3 pounds.
*Increase daily resting metabolic rate in all of the trained muscle by about 1.5 calories per pound (from 5.7 calories per pound to 7.2 calories per pound).
*Increase overall resting metabolism by about 7%.
It makes sense that muscle tissue subjected to regular strength training has a higher metabolic rate than untrained muscle tissue. Our research indicates that regular strength training elicits an increased rate of muscle protein synthesis,4 which should elevate tissue energy usage throughout the day. In other words, strength exercise appears to have an elevating effect on muscle tissue metabolism (e.g., 1.5 calories per pound of muscle per day), and this relatively small increase multiplied by all of the trained skeletal muscle leads to a significantly higher resting metabolic rate.
This explanation appears to be more reasonable than assuming that new muscle tissue uses 35 calories per pound per day, or that trained skeletal muscle still uses only 5.7 calories per pound per day.
Strength Training Increases RMR
Based on the classic research studies conducted at Tufts University and the University of Maryland, standard programs of progressive resistance exercise can increase lean (muscle) weight by 3.0 to 3.5 pounds and resting metabolic rate by 6.8 to 7.7 % after three to four months of regular training, respectively. It is postulated that the increased resting metabolism results from a small increase in energy usage by all of the strength-trained skeletal muscle.
If this is an accurate assumption, strength-trained muscle may use approximately 1.5 more calories per pound per day than untrained muscle (7.2 vs 5.7 calories per pound per day). Such an adaptation could account for the approximately 7 to 8 % elevation in resting metabolism observed in the reported research studies.
Strength training does have a significant elevating effect on resting metabolic rate and is, therefore, a highly beneficial exercise for increasing daily calorie usage and enhancing fat loss. It would appear that the metabolic increase occurs in all of the strength-trained muscle tissue, and that the additional energy usage may be about 1.5 calories per pound of muscle per day.
Campbell, W., M. Crim, V. Young and W. Evans. Increased energy requirements and changes in body composition with resistance training in older adults. American Journal of Clinical Nutrition 60: 167-175, 1994.
Kolata, G. Ultimate Fitness: The quest for truth about exercise and health. Farrar, Straus and Giroux: New York, N.Y., 2003.
Paffenbarger, R., and E. Olsen. Lifefit: An Effective Exercise Program for Optimal Health and A Longer Life. Human Kinetics: Champaign, Ill., 1996.
Pikosky, M., A. Faigenbaum, W. Westcott and N. Rodriguez. Effects of resistance training on protein utilization in healthy children. Medicine and Science in Sports and Exercise 34 (5): 820-827, 2002.
Pratley, R., B. Nicklas, M. Rubin, J. Miller, A. Smith, M. Smith, B. Hurley and A. Goldberg. Strength training increases resting metabolic rate and norepinephrine levels in healthy 50- to 65-year-old men. Journal of Applied Physiology 76: 133-137, 1994.
I hope you enjoyed this article by Dr. Westcott. Now, get thee to the gym and hit those weights.
Lift slowly. Lift heavy (for you). Lift infrequently (twice a week or once every 5 days).
And remember, don’t try – DO!