By Caitlin Mason, Ph.D.

Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.
Dr. Mason is a postdoctoral research fellow at the Fred Hutchinson Cancer Research Center in Seattle, WA. With a background in epidemiology, her research focuses primarily on understanding the mechanisms that link nutrition, exercise, and body composition to chronic disease risk, including cancer.

This commentary presents Dr. Mason’s views associated with a research article she and her colleagues published in the April, 2013 issue of ACSM’s Medicine and Science in Sports and Exercise® (MSSE).

Lifestyle changes leading to modest weight loss of 5-10% are generally sufficient to yield significant improvements in a variety of chronic disease risk factors and are widely recommended. During weight loss, however, a higher ratio of muscle-to-fat mass is lost in older compared to younger adults. Thus, the potential for muscle loss is sometimes a deterrent to prescribed weight loss for overweight and obese older adults, particularly those with or at risk of sarcopenia.

Sarcopenia is the age-related loss of skeletal muscle mass that is associated with a heightened risk of disability. Approximately 30% of individuals over 60 years of age and as many as 50% of people over 80 years are at increased risk of mobility limitations, frailty, falls and fractures due to sarcopenia. Sarcopenic obesity, a term describing the presence of both obesity and low muscle mass, poses an even greater risk of disability. Although muscle loss is an inevitable consequence of aging, considerable differences exist between individuals. Some research has suggested that vitamin D may play a role in sarcopenia. For example, blood levels of vitamin D have been positively associated with muscle mass, muscle strength and physical performance, while improvements in physical functioning and reduced risk of falls have been demonstrated in older adults after vitamin D supplementation.

In our recent study published in MSSE, we investigated whether blood levels of vitamin D influenced the loss of total and appendicular (arms and legs) lean mass in 439 overweight and obese women 50-75 years of age who were undergoing 12 months of either: i) dietary caloric restriction (goal: 10% weight loss), ii) aerobic exercise (goal: 45 minutes/day, 5 days/week of moderate-to-vigorous activity), iii) a combination of diet and exercise, or iv) no lifestyle change.

Although higher levels of blood vitamin D were associated with greater muscle mass at the start of the study, higher vitamin D levels did not protect against the loss of lean mass during weight loss. However, we showed that when added to a dietary weight loss program, regular aerobic exercise can help preserve lean mass while still achieving significant and meaningful weight loss and improvements in metabolic risk factors. Thus, regular moderate-to-vigorous aerobic activity should be considered a viable strategy to counteract the potentially negative effects of weight loss interventions among older adults.

While resistance exercise is typically considered the best approach for preserving muscle mass with aging, its ability to promote weight loss, especially in older women, has not been shown. Future studies should investigate whether the addition of resistance training, and at what dose, may offer additional benefits for preserving both muscle mass and muscle function during weight loss.

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