The Hopkins team showed, in a study to be published in the June issue of the American Journal of Preventive Medicine, that after six months of aerobic exercise on a treadmill, bicycle or stepper, plus weightlifting, subjects experienced better overall fitness and fat loss without much change in bone mineral density. A more detailed analysis revealed slight gains in bone mass, of 1 percent to 2 percent, for those who exercised hardest and showed the greatest increases in aerobic fitness, muscle strength and muscle tissue.
The Hopkins study is believed to be the first to evaluate the effects of exercise independently from other factors, primarily diet, on bone mineral density, a strong gauge of bone health, against the risk of osteoporosis and bone fracture. Indeed, the researchers believe that more intense exercise may demonstrate significantly increased bone mass.
"Older people are very concerned about how best to reduce their body fat as a means of preventing other health problems, such as heart disease and diabetes," says lead study investigator and exercise physiologist Kerry Stewart, Ed.D., a professor of medicine and director of clinical exercise physiology and heart health programs at The Johns Hopkins University School of Medicine and its Heart Institute. "However, excess fat does have the benefit of maintaining bone mass. But fat loss through diet alone can lead to loss of bone, worsening the body's natural bone loss due to aging, a major risk factor for bone fractures."
According to Stewart, most existing studies about the effects of exercise on bone had several limitations to their findings. Many enrolled only wome
Contact: David March
Johns Hopkins Medical Institutions