20% Caloric Restriction did not Impact Bone Health nor Exercise-Induced Elevations in Bone Mass in Young Female Rats

The purpose of this study was to determine if a 6-week 20% caloric restrictive (CR) diet, with or without resistance training, would impact bone health in growing young female rats. Forty female rats (~ 5 wks old) were randomly divided into the following groups: baseline (n = 8), sedentary fed a normal diet (N, n = 8), sedentary fed a 20% CR diet (D, n = 8), resistance trained fed a normal diet (NT, n = 8), and resistance trained fed a 20% CR diet (DT, n = 8). The exercise groups were conditioned to climb a vertical ladder 4 consecutive times (per exercise session) with weights appended to their tail 3 days/wk for a total of 6 wks. Tibial bone mineral density (BMD) was assessed via dual-energy x-ray absorptiometry scans. After 6 wks, the body mass (mean ± SD) for CR fed groups (D = 232.6 ± 26.3 g & DT = 216.6 ± 17.9 g) were significantly lower than the normal fed groups (N = 266.1 ± 31.5 g & NT = 251.9 ± 23.4 g). Tibial BMD (in g/cm²) for the sedentary CR group (D = 0.184 ± 0.005) was not significantly different compared to the sedentary normal fed group (N = 0.184 ± 0.010). Resistance training resulted in an elevation in BMD (NT = 0.195 ± 0.011 & DT = 0.192 ± 0.004) compared to the sedentary groups). The results indicate that during the growth period in young female rats, a 20% CR diet did not impact tibia BMD, nor did CR alter the resistance training-induced elevation in BMD.