Changes in Body Composition with Aging

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Aging Muscle and Fat

As a man ages, he loses muscle mass, typically about 0.5- 1.0% per year after the age of 40.1 These loses may seem very small, but by the age of 50 these losses add up to roughly a 5-10% loss in muscle mass. Additionally, this loss in muscle mass is typically accompanied by an increase in fat mass, especially abdominal fat.

The term for the age-related decline in muscle mass is sacropenia. According to one study, approximately one in every two men over the age of 60 suffer from moderate sacropenia.2 Sacropenia causes a decrease in metabolism and a loss in functional strength.

 


 
What Effects Does Losing Muscle Mass Have?
Body Changes

This loss in muscle mass does two things. First, it lowers your resting metabolism so you burn fewer calories throughout the day. This decrease in resting metabolism makes it even more difficult to avoid putting on excess fat. Second, your muscle strength decreases which can lead to functional disability.

What Effects Does Gaining Fat Mass Have?

An increase in fat, especially, abdominal fat induces insulin resistance, leading eventually to diabetes mellitus, atherosclerosis, and an increased risk of cardiovascular disease. An increase in fat mass also suppresses both testosterone and growth hormone secretion, which may exarcerbate age-related declines in these vital hormones.

 

How to Minimize Changes in Body Composition Associated with Aging

  • Resistance Exercise – Resistance exercise maintains or increases lean muscle mass and. As a result, it maintains or increases resting metabolism, preventing increases in unwanted fat mass. In fact, resistance training is the most effective way to prevent the muscle mass and strength losses that accompany aging.
  • Aerobic Exercise – Aerobic exercise also maintains or increases lean body mass, though, not to the same extent as resistance training. Aerobic exercise typically burns more calories than resistance exercise of the same intensity during exercise, helping prevent increases in fat mass associated with aging.
  • Testosterone Replacement Therapy – For men with low testosterone, testosterone replacement therapy can produce a moderate increase in muscle mass and moderate decrease in fat mass. Nevertheless, testosterone replacement therapy will not make up for poor diet, lack of exercise, and a generally unhealthy lifestyle.

 

1. Lunenfield B, Gooren LJG, Morales A, Morley JE. Textbook of Men’s Health and Aging. 2nd ed. London, UK 2007.
2. Janssen I, Heymsfield SB, Ross R. Low relative skeletal muscle mass (sarcopenia) in older persons is associated with functional impairment and physical disability. J Am Geriatr Soc. May 2002; 50 (5): 889-896.