Weight loss can mean bone loss for older women

By Amy Norton

NEW YORK (Reuters Health) - Losing weight around the time of menopause may accelerate the bone loss that women typically see as they age, a new study suggests.

The findings do not mean that overweight women shouldn't try to shed pounds, researchers caution. But they do suggest that middle-age or older women who lose weight need to pay extra attention to their bone health.

The study, published in the Journal of Clinical Endocrinology & Metabolism, involved 373 women ages 44 to 50. About half were randomly assigned to follow a low-fat diet and get regular exercise to prevent menopausal weight gain, or to lose pounds if they were already overweight.

The other half of the women maintained their usual lifestyle and served as a "control" group.

Over the next five years, women in the diet-and-exercise group lost a modest amount of weight, on average, while those in the comparison group typically gained weight.

However, the weight loss was accompanied by a statistically significant greater decline in bone density in the hip.

"Women need to keep in mind that when you lose weight, you probably will lose some bone mass," said study co-author Dr. Jane A. Cauley, a professor of epidemiology at the University of Pittsburgh Graduate School of Public Health.

"I would never want to discourage women, or men, from losing weight if they need to," Cauley said in an interview. "But I think the message should be, 'Be cautious about your bone health.'"

That, she noted, means getting a bone-density scan to gauge your bone health and risk of osteoporosis, as well as taking lifestyle measures to protect your bone mass. Women who change their diets to lose weight should take care to include enough calcium-rich foods -- like skim milk and yogurt -- and adequate vitamin D.

Experts recommend that adults older than 50 get 1,200 mg of calcium each day and up to 1,000 IU of vitamin D to protect their bone health.

Exercise can also help maintain bone mass, though the type of activity may be key. In the study, Cauley pointed out, the women who lost weight mainly used walking as their exercise; such low-impact, aerobic activity may not be enough to counter the bone loss that comes with losing weight, she explained.

Other studies have shown that the best bone-protecting activities are weight-bearing exercises that make the body work against gravity, like weight-lifting and climbing stairs. Cauley said she and her colleagues plan to study whether adding strength-training to women's exercise regimens helps lessen any bone loss as they shed pounds.

SOURCE: Journal of Clinical Endocrinology & Metabolism, October 2007.