The contributions of weight loss and increased physical fitness to improvements in health-related quality of life

The relative contribution of obesity versus poor fitness to adverse health outcomes and diminished quality of life remains an area of controversy. Indeed, some researchers contend that poor cardiorespiratory fitness represents a greater threat to health and health-related quality of life than excess body weight. We addressed this issue by providing 298 obese 50–75 year-old women with a six-month lifestyle intervention that incorporated a low-calorie eating pattern coupled with an aerobic exercise program consisting of 30 min/day of brisk walking. The results showed that weight loss exhibited a significant individual contribution to improvements in seven of the nine domains of quality of life assessed by the Medical Outcomes Study Short Form (SF-36). With the exception of physical functioning, however, physical fitness did not significantly contribute to improvements beyond the effects weight loss. Moreover, weight loss functioned as a full mediator of the association between increases in physical fitness and improvements in general health, vitality, and change in health relative to the previous year. Collectively, these findings suggest that for treatment-seeking obese individuals, weight loss rather than increased fitness contributes significantly to improvements in health-related quality of life.