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Effects of Resistance Exercise on Lean Weight, Fat Weight, and Metabolism

In 1994, two landmark research studies demonstrated that resistance exercise increases resting energy requirements, resulting in concurrent lean weight gain and fat weight loss.2,6 Pratley and associates6 at the University of Maryland trained 13 men over age 50 with 1 set of 14 resistance machine exercises, 3 days a week, for a period of 16 weeks. On average, the program participants added 3.5 lbs of lean weight, lost 4.2 lbs of fat weight, and increased their resting metabolic rate by 7.7%.

That same year, Campbell and colleagues2 at Tufts University trained 12 men and women over age 55 with 3 sets of 4 resistance machine exercises, 3 days a week, for a period of 12 weeks. On average, the study subjects added 3.1 lbs of lean weight, lost 4.0 lbs of fat weight, and increased their resting metabolic rate by 6.8%.

In 2000, Hunter and co-researchers3 at the University of Alabama trained 15 men and women over age 60 with 2 sets of 10 resistance machine exercises, 3 days a week, for a period of 26 weeks. On average, these individuals experienced a 4.4-lb increase in lean weight, a 5.9-lb decrease in fat weight, and a 6.8% elevation in resting energy expenditure.

More recently, Westcott and colleagues10 examined the effects of combined resistance exercise and aerobic activity on lean weight and fat weight in more than 1,600 men and women between 21 and 80 years of age. The program participants performed 1 set of 10 resistance machine exercises and 20 minutes of walking or cycling, 2 or 3 days a week, for a period of 10 weeks. Subjects who trained twice a week added 3.1 lbs of lean weight and lost 3.2 lbs of fat weight. Subjects who trained 3 times a week added 3.1 lbs of lean weight and lost 4.4 lbs of fat weight.

The results of these studies indicated that through the first four months of strength training (with or without aerobic activity) lean weight increased at a rate of just under 0.3 lbs per week and fat weight decreased at a rate of just over 0.3 lbs per week, with an associated elevation in resting metabolic rate of approximately 7%. Most likely, the 7% increase in resting metabolic rate (equivalent to about 100 calories per day) played a major role in the fat weight reduction.

Under normal nutrition patterns, resistance training appears to increase resting metabolic rate and improve body composition, with concurrent lean weight gain and fat weight loss. The question then becomes, can resistance training prevent the lean weight loss, resting metabolic rate reduction, and subsequent weight regain associated with reduced calorie diet plans?1,4,5

A 2013 weight loss study8 combined a protein-rich, calorie-restricted diet plan (1,200 to 1,500 kcals/day for women; 1,500 to 1,800 kcals/day for men) with a basic exercise program (1 set of 9 resistance machine exercises and 15 minutes of aerobic activity). After 10 weeks of training, the 45 men and women (mean age 60 years) who completed the diet and exercise program averaged a 1.7-lb increase in lean weight and a 7.1-lb decrease in fat weight, for a 2.9-point improvement in percent body fat. Although these findings demonstrated concurrent lean weight gain and fat weight loss during a period of reduced calorie intake, the rate of lean weight gain was much lower than that attained in similar strength training programs without calorie reduction.2,6

Follow-up research conducted by Westcott and colleagues9 provided additional information on lean weight gain in adult weight loss participants. Similar to the previous study,8 37 men and women (mean age 56 years) followed a protein-rich, calorie-restricted diet plan (1,200 to 1,500 kcals/day for women; 1,500 to 1,800 kcals/day for men) and performed a basic exercise program (1 set of 9 resistance machine exercises and 20 minutes of aerobic activity). During the first 12 weeks, the study participants averaged a 0.8-lb increase in lean weight and a 7.0-lb decrease in fat weight, for a 2.6-point improvement in percent body fat. During the second 12 weeks of the same diet and exercise program the same subjects experienced a 2.9-lb increase in lean weight and a 7.1-lb decrease in fat weight, for a 3.1-point improvement in percent body fat. Although the program participants lost the same amount of fat weight during both 3-month training periods, they experienced significantly greater lean weight gain during the second 12-week session. Also, the latter session lean weight gain was similar to the lean weight increases reported in strength training studies that did not involve dietary changes.3,10

It seems that during the initial phase of reduced calorie diet plans, muscle-building processes proceed at a relatively slow rate. However, as the body adapts to lower food consumption, it appears that the rate of lean weight gain accelerates and is similar to that experienced during standard strength programs without caloric restriction.

Practical Application

Approximately 70% of American adults are attempting to lower their body weight by means of reduced-calorie diet plans.7 Unfortunately, about 25% of the weight lost through dieting alone is lean tissue,1 which results in resting metabolic rate reduction and subsequent return to pre-diet body weight.4,11 Research demonstrates that resistance exercise is effective for increasing lean weight and resting metabolic rate, and for decreasing fat weight.2,3,6 Studies also show that protein-rich, reduced-calorie diets combined with resistance exercise may result in concurrent fat weight loss and lean weight gain.8,9 Additionally, the rate of lean weight gain appears to increase as the body adapts to restricted food consumption.9 It is therefore suggested that individuals who attempt to lower their body weight through caloric reduction implement a protein-rich diet plan and perform regular resistance exercise to concurrently increase lean weight and decrease fat weight for improved body composition and weight management. 

Wayne L. Westcott, Ph.D., is a professor of Exercise Science at Quincy College in Quincy, MA. He is an active member of the New England Chapter of the American College of Sports Medicine and author of 28 books on strength training.

References

1. Ballor D, Poehlman E. Exercise training enhances fat-free mass preservation during diet-induced weight loss: a meta-analytic finding. Inter J Obes. 1994;18:35-40.

2. Campbell W W, Crim MC, Young VR, Evans WJ. Increased energy requirements and changes in body composition with resistance training in older adults. Am J Clin Nutr. 1994;60:167-175.

3. Hunter GR, Wetzstein CJ, Fields DA, et al. Resistance training increases total energy expenditure and free-living physical activity in older adults. J Appl Physiol. 2000; 89:977-984.

4. Mann T, Tomiyama AJ, Westling E, et al. Medicare's search for obesity treatments: diets are not the answer. Am Psychol. 2007;62(3):220-233.

5. Mettler S, Mitchell N, Tipton KD. Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc. 2010;42(2):326-337.

6. Pratley R, Nicklas B, Rubin M, et al. Strength training increases resting metabolic rate and norepinephrine levels in healthy 50- to 65-yr-old men. J Appl Physiol. 1994; 76(1):133-137.

7. Serdula MK, Mokdad AH, Williamson DF, et al. Prevalence of attempting weight loss and strategies for controlling weight. JAMA. 1999;282(14):1353-1358.

8. Westcott WL, Apovian CM, Puhala K, et al. Nutrition programs enhance exercise effects on body composition and resting blood pressure. Phys Sports Med. 2013;41(3):85-91.

9. Westcott WL, Colligan A, Puhala K, et al. Exercise and nutrition effects on body composition and blood measures in overweight adults. J Exerc Physiol. 2017;20(1):200-220.

10. Westcott WL, Winett RA, Annesi JJ, et al. Prescribing physical activity: applying the ACSM protocols for exercise type, intensity, and duration across 3 training frequencies. Phys Sports Med. 2009;2(37):51-58.

11. Wolfe I. The unappreciated role of muscle in health and disease. Am J Clin Nutr. 2006; 84:475-482.

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