Bone responses to body weight and moderate treadmill exercising in growing male obese (fa/fa) and lean Zucker rats.

OBJECTIVE To evaluate if exercise in a young growing model of obesity would be able to reduce adiposity without adversely affecting bone. METHODS Obese (fa/fa) and lean (Fa/Fa) male Zucker rats were randomly assigned (n=8-9 rats/group) to no exercise or to a moderate treadmill exercise regimen consisting of a speed of 20 m/min for approximately 1 h, 5 d/wk for 9 wks. Bone morphometry, total bone ash, and bone strength by three-point bending test were determined in the femur and the tibia. Serum alkaline phosphatase was determined using calorimetric enzyme assays. Serum osteocalcin, deoxypyridinoline (DPD), and pyridinoline (PYD) crosslinks were measured using enzyme immunoassays. Various blood chemistry measurements were determined including: serum glucose, insulin, and leptin. RESULTS Growing obese (fa/fa) Zucker rats have long bone ash comparable to lean Zucker rats, although bone size is reduced. Moderate treadmill running successfully reduced body weight without increasing muscle mass, but did not attenuate the reduction in bone growth or promote greater bone mass and strength in obese Zucker rats. CONCLUSIONS Moderate treadmill running for 9 wks successfully reduced the body weight of obese Zucker rats by 7.5% without negatively affecting bone.