Little is known about the health benefits that may be obtained by breaking prolonged periods in a seated position, especially during postprandial periods. We hypothesized that reduced sitting time magnifies the positive effects of a lifestyle based reduction of body fat, as well as reducing metabolic risk factors for overweight and obese women. Middle-aged women (n=45, aged 46.8 ± 6.5 yrs) participated in a 12-week lifestyle intervention, consisting of combined exercise and behavior modification. Based on their average time spent engaged in sedentary behaviors (i.e., sitting and lying) during postprandial periods, participants were retrospectively classified as the least sedentary group (LSG) moderately sedentary group (MSG) and highly sedentary group (HSG). Two-way RMANOVA showed significant group-by-time interactions for body composition. Following the intervention, improvements in body weight, body mass index, percentage body fat, and waist circumference were greatest in the LSG, followed by those in the MSG and HSG. Similar group-by-time interactions were associated with several metabolic risk factors. Improvements in HDL-C, fasting blood glucose and insulin levels, HOMA-IR, and the prevalence of metabolic syndrome were observed to be greatest in the LSG, followed by those of the MSG and HSG. Our findings suggest that breaking prolonged sitting time should be encouraged in order to augment the health benefits of exercise training for the treatment of obesity-related metabolic risk factors in middle-aged women.