For Americans, Age 55 to 75, Bone Mass Gains Track Gains in Overall Fitness

WEDNESDAY, June 8 (HealthDay News) -- Exercise helps maintain and, in some cases, improve bone mass in people ages 55 to 75, according to a new study that challenges the idea that fat-burning exercise harms bone health in this age group.

"Fat loss with exercise did not result in a loss of bone mass, a problem commonly seen when patients lose weight with diet alone," co-author and endocrinologist Dr. Suzanne Jan de Beur, an assistant professor at Johns Hopkins University, said in a statement.

The study of 104 men and women found that six months of aerobic exercise using a bicycle, treadmill or stepper, combined with weightlifting, resulted in better overall fitness and fat loss without significant change in bone mineral density.   
In fact, the study volunteers who exercised the hardest and had the greatest increases in aerobic fitness, muscle strength and muscle tissue showed bone mass increases of 1 percent to 2 percent, the researchers found.   

This is believed to be the first study to examine the impact of exercise independent of other factors, primarily diet, on bone mineral density and the risk of osteoporosis and fractures, the researchers said.  

"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. However, excess fat does have the benefit of maintaining bone mass," study lead investigator Kerry Stewart, professor of medicine and director of clinical exercise physiology and heart health programs at Johns Hopkins University School of Medicine and its Heart Institute, explained in a prepared statement.  

"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," she said.  

"Our results show that moderate-intensity exercise can increase fitness and reduce body fat, which are important for overall health, but gains in bone density were found only among those who achieved the greatest gains in fitness in six months," added de Beur, who specializes in bone health.  

She recommends that older people either exercise at a higher level of intensity or for longer than six months to achieve a substantial increase in bone density.  

The study appears in the June issue of the American Journal of Preventive Medicine.