The effects of dietary-induced obesity on the biomechanical properties of femora in male rats

OBJECTIVE: To assess the effects of diet-induced obesity (DIO), on the biomechanical and biochemical properties of the femur in mature male rats. DESIGN AND SUBJECTS: Two groups of male rats were studied. The DIO experimental group was fed a high caloric diet and a 31% sucrose solution as drinking fluid for a month, whereas the control group was fed lab chow and tap water. MEASUREMENT: Body weight; body water; lean body mass; femoral length; average cortical thickness; outer anteroposterior diameter; outer mediolateral diameter; cortex area; moment of inertia; cortical and cancellous bone hydration; tendon and muscle hydration; ash content of cortical and cancellous bone; ultimate load; deflection at ultimate load; ultimate strength; stiffness; elastic modulus and energy absorption capacity. RESULTS: 'Gainers' (final body weight in excess of three standard error of mean of the controls) were 19.1% heavier, with higher body fat, whereas body water, lean body mass, hydration of cancellous bone and ash content of cortical bone were lower, when compared to controls. Rats that failed to gain weight, despite the high caloric diet, were termed 'resisters' (weight gain less than three standard error of mean of the controls). Ultimate load, deflection at ultimate load and femoral energy absorption capacity were significantly higher in the experimental group when compared to the controls. However, no differences were found among the groups with respect to ultimate stress and stiffness. CONCLUSION: The weight gain produced by DIO may lead to bone adaptation and improved biomechanics.