Effects of high‐fat diet and treadmill running on bone marrow fat and bone properties in young male mice

We investigated the effects of a high-fat diet (HFD) and treadmill running on bone marrow fat (BMF) and bone properties in mice. Four-week-old male mice (n = 6/group) were assigned to four groups: standard diet (STD) or HFD (60% kcal from fat), under sedentary or exercise conditions. Mice performed treadmill running (6-18 m/min, 30 min/day, 5 days/week) for 16 weeks. At 20 weeks, body weight, adipose tissue mass, bone mineral density (BMD), bone strength, histomorphometry, and bone turnover markers were assessed. HFD significantly increased body weight and adipose tissue mass, whereas exercise attenuated HFD-induced weight gain. Absolute BMD was unaffected by diet but lower in exercised mice. Weight-adjusted BMD was lower in HFD-fed mice and higher in exercised mice. BMF was elevated by HFD and was not reduced by exercise. The resorption marker was increased by HFD and was not attenuated by exercise, whereas the formation marker was elevated only in exercised mice. The ratio of bone resorption to bone formation markers was higher in HFD-fed mice. No significant diet × exercise interactions were observed for turnover markers. In conclusion, HFD during growth increases BMF, whereas treadmill running attenuates HFD-induced weight gain but does not prevent increases in BMF.