The Journals of Gerontology Series A: Biological Sciences and Medical Sciences Advance Access published online on March 10, 2009
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, doi:10.1093/gerona/glp007
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Moderate Exercise Attenuates the Loss of Skeletal Muscle Mass That Occurs With Intentional Caloric Restriction–Induced Weight Loss in Older, Overweight to Obese Adults
Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh School of Medicine, Pennsylvania
Address correspondence to Bret H. Goodpaster, PhD, Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh School of Medicine, N810 Montefiore Hospital, 3459 Fifth Avenue, Pittsburgh, PA 15213. Email: bgood{at}pitt.edu
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Abstract |
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Background: Aging is associated with a loss of muscle mass and increased body fat. The effects of diet-induced weight loss on muscle mass in older adults are not clear.
Purpose: This study examined the effects of diet-induced weight loss, alone and in combination with moderate aerobic exercise, on skeletal muscle mass in older adults.
Methods: Twenty-nine overweight to obese (body mass index = 31.8 ± 3.3 kg/m2) older (67.2 ± 4.2 years) men (n = 13) and women (n = 16) completed a 4-month intervention consisting of diet-induced weight loss alone (WL; n = 11) or with exercise (WL/EX; n = 18). The WL intervention consisted of a low-fat, 500–1,000 kcal/d caloric restriction. The WL/EX intervention included the WL intervention with the addition of aerobic exercise, moderate-intensity walking, three to five times per week for 35–45 minutes per session. Whole-body dual-energy x-ray absorptiometry, thigh computed tomography (CT), and percutaneous muscle biopsy were performed to assess changes in skeletal muscle mass at the whole-body, regional, and cellular level, respectively.
Results: Mixed analysis of variance demonstrated that both groups had similar decreases in bodyweight (WL, –9.2% ± 1.0%; WL/EX, –9.1% ± 1.0%) and whole-body fat mass (WL, –16.5%, WL/EX, –20.7%). However, whole-body fat-free mass decreased significantly (p < .05) in WL (–4.3% ± 1.2%) but not in WL/EX (–1.1% ± 1.0%). Thigh muscle cross-sectional area by CT decreased in both groups (WL, –5.2% ± 1.1%; WL/EX, –3.0% ± 1.0%) and was not statistically different between groups. Type I muscle fiber area decreased in WL (–19.2% ± 7.9%, p = .01) but remained unchanged in WL/EX (3.4% ± 7.5%). Similar patterns were observed in type II fibers (WL, –16.6% ± 4.0%; WL/EX, –0.2% ± 6.5%).
Conclusion: Diet-induced weight loss significantly decreased muscle mass in older adults. However, the addition of moderate aerobic exercise to intentional weight loss attenuated the loss of muscle mass.
Keywords Weight loss; Aerobic exercise; Obese; Muscle
Received: June 15, 2008; Accepted: December 23, 2008