Sex differences in the effects of voluntary activity on sucrose-induced obesity

Sedentary, adult rats of both sexes fed Purina chow and a 32% sucrose solution overate, gained excess weight and had higher Lee Indexes of obesity than control animals fed only Purina chow. The magnitude of these effects was similar in the males and females. Animals of both sexes fed the sucrose diet showed a slower rate of weight loss during food deprivation than the chow controls. Access to an activity wheel led to a reduction in caloric intake and the elimination of obesity in male rats. In the chow fed male rats activity led to a smaller, transient suppression in caloric intake and a slightly lower level of body weight than the sedentary chow controls. Access to activity did not affect body weight in the female rats in either dietary condition. Rather, both active groups of female rats appeared to compensate for the energy cost of voluntary activity by a small increase in food consumption. Long-term exposure to activity was associated with more rapid weight loss during food deprivation in both males and females. These data reveal that high levels of activity and obesity can co-exist when normal female rats are fed a palatable diet but that activity eliminates this form of obesity in the male rat.