Increased Muscle = Increased Resting Metabolic Rates = Weight Loss

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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:

Research Study	Strength Training Program	Training Frequency	Training Duration	Change Muscle Tissue	Change Resting Metabolism
Campbell, et al. Tufts University	4 exercises; 3 sets; 8-12 reps	3 times per week	12 weeks	+3.1 lbs.	+6.8%
Pratley, et al. University of Maryland	14 exercises; 1 set/2 sets; 10-15 reps	3 times per week	16 weeks	+3.5 lbs.	+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.

References

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.

About Wayne Westcott

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