Exercise-induced weight loss does not lead to declines in bone mineral density at fracture-relevant sites after 12 months, but weight through calorie restriction does, according to a randomized, controlled trial of 48 adults.
Regional BMD at the total hip and at the intertrochanter decreased significantly more with calorie restriction than they did without in a control group. BMD did not change significantly with exercise, compared with controls, study investigators reported.
The researchers randomized 48 nonobese but mostly overweight adults aged 50–60 years to three groups. The 19 subjects in the calorie restriction group decreased energy intake by 16% during the first 3 months and by 20% during the subsequent 9 months. The 19 subjects in the exercise group decreased overall energy intake by the same amount through exercise; they exercised a mean of 5.8 times per week for 62.5 minutes per session. The most common modes of exercise were walking and/or jogging, followed by elliptical training and cycling.
The remaining 10 participants did not change their diet or exercise habits, wrote Dr. Dennis T. Villareal of Washington University, St. Louis, and colleagues (Arch. Intern. Med. 2006;166:2502–10).
Overall, in the calorie restriction group, BMD decreased 2.2% at the lumbar spine, 2.2% in the total hip, and 2.1% in the intertrochanter.
Markers of bone turnover increased significantly in both the calorie-restriction and exercise groups.
Relative reductions in body weight after 1 year were similar with calorie restriction (10.7%) and with exercise (8.4%), whereas the control group did not lose weight (1.2%).
These findings indicate that exercise was associated with weight loss but not loss of BMD, whereas weight loss due to calorie restriction was significantly associated with changes in hip BMD.
The most practical approach to weight loss is a combined regimen of calorie restriction and exercise, the researchers noted.