Effects of Weight Loss on Bone Mineral Density in Rats

Objective: To evaluate the effects of weight loss on bone mineral density (BMD). Methods: Eight-week-old female rats were divided into 4 groups: Those in Group A received a restricted diet for 4 weeks; those in Group B received a restricted diet and were treated with estrogen; those in Group C were castrated; and those in Group D underwent sham operations. The rat's body weight (BW) and vaginal smears were checked, and their femoral BMD was measured. Results: The BW and BMD at 12 weeks were lower in Groups A and B than in Groups C and D; thereafter, however, these values increased for Groups A and B, but were still lower than those in Group D even at 20 weeks. In Group C, the BMD did not decrease, but it was significantly lower than that in Group D at 16 and 20 weeks. Group A showed continuous diestrus 2 weeks after dietary restriction began, but recovered to a 4-day cycle 2 weeks after the initiation of free food consumption. Conclusion: Weight loss had a greater effect on BMD than hypoestrogenism.