Frequent weight loss may weaken men's bones

NEW YORK (Reuters Health) - Weight cycling in adulthood may lead to fragile bones later in life, according to a new study of 4,601 men followed for 28 years.

The more frequently men slimmed down and regained weight between the ages of 25 and 50, the more likely they were to suffer a fractured forearm after age 50, Dr. Anne Johanne Sogaard of the Norwegian Institute of Public Health in Oslo and colleagues found.

Weight cycling could increase skeletal fragility by causing microscopic damage to bone structure, or it could also boost men's fall risk by weakening muscles, Sogaard noted in emailed comments to Reuters Health.

Sogaard and her team had previously found that among the group of men initially examined in 1972-1973 and then later in 2000, those who had lost weight more frequently, and lost more weight with each slimming bout, were more likely to develop metabolic syndrome and diabetes.

In the current study, in the American Journal of Epidemiology, the researchers investigated whether weight cycling was related to the risk of forearm fracture, "an early and sensitive marker of male skeletal fragility."

Among men who reported no weight loss episodes before age 50, about 17-18 percent suffered forearm fractures. The rate was 35-43 percent among men who had lost weight four or more times, depending to some extent on the amount lost.

After accounting for other factors, losing weight four or more times before the age of 50 nearly tripled the risk of forearm fracture after 50.

People who want to make sure their bones stay strong when they lose weight should always be sure to exercise as well as diet, Sogaard said. "We know that weight-bearing activities, weight-training and exercise with varied loadings (e.g. squash, badminton, tennis) are favorable for muscles (and) balance, as well as bones."

Also, Sogaard noted, people who lose weight and then regain it often wind up weighing more than they did before they started trying to slim down. "If you want to lose weight, the crucial thing is to be serious (and) realistic regarding how much, and determined to change life-style," she said -- not just jump on a casual diet.

SOURCE: American Journal of Epidemiology, April 15, 2008.