Effects of dietary fat levels and feeding durations on musculoskeletal health in female rats

Objectives: This study evaluates the effects of dietary fat levels and feeding durations on body composition, bone properties, and endocrine factors in female rats. Methods: Forty-eight 3-month-old female rats were assigned into a 2 (low-fat diet vs. high-fat diet) × 2 (4-month vs. 8-month feeding duration) factorial design. The body composition, bone matrix and microstructure, and endocrine factors were examined. Results: Compared to the low-fat diet, the high-fat diet (i) increased the % fat mass, femoral mineral density, trabecular and cortical formation and erosion, osteoblast and osteoclast numbers, insulin-like growth factor-I, and leptin and (ii) decreased the % fat-free mass, bone strength, and trabecular and cortical bone volume and thickness. Relative to the 4-month feeding duration, the 8-month feeding duration (i) increased the femoral mineral density, trabecular separation, formation and erosion, endocortical formation rate, and osteoclast number and (ii) decreased the trabecular bone volume, thickness, and number, osteoblast number, and adiponectin. Interactions between dietary fat level and feeding duration were observed in bone strength, trabecular thickness and formation rate, as well as cortical bone volume and mineral apposition rate. Conclusions: Both dietary fat level and feeding duration affect the bone mass and microstructure in female rats, possibly through the modulation of body composition and endocrine factors.