INFLUENCE OF FAT INTAKE AND CALORIC RESTRICTION ON BONE IN AGING MALE-RATS

Caloric and fat intake may have important skeletal consequences. To ev aluate this possibility, skeletal effects of adult-onset caloric restr iction (CR) at differing fat intakes were assessed in male Lobund-Wist ar rats. At age 17 months, two groups of animals received an anti-obes ity diet, restricted approximate to 35% from individual ad libitum bas eline calorie consumption, and two groups received a diet approximate to 50% restricted. Dietary fat concentrations were 5, 15, 15, and 25% by weight, respectively. At ages 20, 24, 28, 30 and 32 months, ex vivo femoral bone densitometry and serum biochemical analyses were perform ed. Body weight (BW) decreased with time on CR in each group (p < .005 ), declining faster at the more severe restriction (p = .001). Femoral bone mineral contents (BMC) were also reduced. After adjusting for bo ne area and BW differences among groups, the only significant differen ce was a reduction in distal femur BMC in the 25% fat group subjected to more severe CR (p = .02). No differences were observed in serum par athryoid hormone, calcium, phosphorus, or creatinine. Femoral bone los s occurred with CR. This was entirely accounted for by reduction in BW . Higher dietary fat content did not affect BW in CR animals, but did result in lower distal femur BMC.