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STUDY: Muscle strength and the degree of abdominal obesity were directly related to BMD
JOURNAL: J Int Med 2002;252:000-000.
AUTHORS: Dr. Kerry J. Stewart
ABSTRACT: Although mild exercise has been shown to reduce the risk of heart disease, it does not appear to be osteoprotective, according to findings from a recent study.
COMMENTARY: Mild physical activity does not seem to be "sufficient to hold off or attenuate the age-related decline in bone with aging," said lead author Dr. Kerry J. Stewart, from Johns Hopkins University in Baltimore.
While mild activity and aerobic fitness did not affect bone mineral density (BMD), muscle strength and the degree of abdominal obesity were directly related to BMD, according to the report published in the Journal of Internal Medicine.
Although being fat may be good for bone density, gaining weight is not the answer because of the harmful effects of obesity on many other aspects of health.
Dr. Stewart's team studied the effects of mild physical activity in 38 men and 46 women, 55 to 75 years of age, with high normal blood pressure or mild hypertension. None of the participants exercised on a regular basis.
Neither overall aerobic fitness nor participation in mild physical activity had a significant effect on BMD, the researchers note. But muscle strength, as well as abdominal obesity, was associated with denser bones.
They found that being more fat and having stronger muscle, which is common in fatter people, along with hormone replacement therapy, had the most influence on bone. In particular, having more abdominal fat was most strongly linked to bone density.
Exactly how abdominal obesity may promote increases in BMD is unclear, but Dr. Stewart suggested that the hormone leptin may be involved. Leptin levels tend to be higher in obese people, he explained, and findings from animal studies indicate that leptin increases the activity of bone cells.