Weight loss contributes to BMD decline

Hormone therapy did not provide complete protection; weight loss could contribute to osteoporotic fracture.

Modest weight loss of approximately 10 pounds caused a reduction in bone mineral density in postmenopausal women. This reduction occurred despite weight-bearing exercise, and hormone therapies provided incomplete protection, Wendee Gozansky, MD, MPH, assistant professor of medicine in the division of geriatrics at the University of Colorado Health Sciences Center, told Orthopedics Today.

"It presents a conflict because we want women to lose weight to improve their cardiovascular risk profile, but we don't want to be putting them at risk for osteoporotic fracture," Gozansky said. "Because exercise per se has beneficial effects on BMD, diet-induced weight loss may have an even greater negative impact on bone."

Gozansky and colleagues observed the effects of weight loss and hormone treatment among 94 postmenopausal women. Their results were recently published in The Journal of Clinical Endocrinology & Metabolism.

Supervised exercise training

Sixty-eight women participated in a six-month weight-loss program that included primarily supervised exercise training and one-week periods of reduced calorie intake in the first, third and fifth months. Volunteers were allowed to choose the method of endurance exercise, such as walking or cycling. During the first few weeks researchers gradually increased exercise session duration and intensity with the goal to increase energy expenditure by approximately 400 kcal per day.

Another 26 women were placed in a weight stability arm.

No differences were reported between the two groups in age, age of menopause, previous hormone therapy use, dietary calcium intake, and calcium supplement use. Women who were recruited into the weight loss arm weighed more, had more fat mass, more fat-free mass, and higher BMD.

Using the World Health Organization Criteria, researchers identified 22 women in the weight-loss group and 12 women in the weight-stable group who were osteopenic, and six women in the weight-loss group and five women in the weight-stable group who were osteoporic.

"We need to pay a bit more attention to this. Nearly half of the women in this study had low BMD despite being overweight to obese. Although being underweight is a known risk factor for osteoporosis, being overweight does not guarentee protection," Gozansky said.

Drug treatment

All volunteers were further assigned to placebo (n=29), raloxifene (Evista, Eli Lilly and Company; n=32), or estrogen hormone therapy (n=33).

After the six-month study period, women in the exercise group lost a mean of 4.1 kg compared to a gain of 0.8 kg in the weight-stable group.

In the weight-loss group, BMD was reduced by 1.5% in the placebo group, 0.5% in the raloxifene group and increased by 1.1% in the hormone therapy group.

By contrast, in the weight-stable group, BMD decreased by 0.6% in the placebo group and increased by 0.9% in the raloxifene group and 3% in the hormone therapy group.

For more information:
Gozansky WS, Van Pelt RE, Jankowski CM, et al. Protection of bone mass by estrogens and raloxifene during exercise-induced weight loss. J Clin Endocrinol Metab. 2005;90:52-59.