A structured diet and exercise program promotes favorable changes in weight loss, body composition, and weight maintenance.

Background: A number of diet and exercise programs purport to help promote and maintain weight loss. However, few studies have compared the efficacy of different methods.

Objective: To determine whether adherence to a meal-replacement-based diet program (MRP) with encouragement to increase physical activity is as effective as following a more structured meal-plan-based diet and supervised exercise program (SDE) in sedentary obese women.

Design: Randomized comparative effectiveness trial.

Participants/setting: From July 2007 to October 2008, 90 obese and apparently healthy women completed a 10-week university-based weight loss trial while 77 women from this cohort also completed a 24-week weight maintenance phase.

Intervention: Participants were matched and randomized to participate in an MRP or SDE program.

Main Outcome Measures: Weight loss, health, and fitness-related data were assessed at 0 and 10 weeks on all subjects as well as at 14, 22, and 34 weeks on participants who completed the weight maintenance phase.

Statistical Analyses Performed: Data were analyzed by multivariate analysis of variance for repeated measures.

Results: During the 10-week weight loss phase, moderate and vigorous physical activity levels were significantly higher in the SDE group with no differences observed between groups in daily energy intake. The SDE group lost more weight (-3.1 ± 3.7 vs -1.6 ± 2.5 kg; P = 0.03); fat mass (-2.3 ± 3.5 vs -0.9 ± 1.6 kg; P = 0.02); centimeters from the hips (-4.6 ± 7 vs -0.2 ± 6 cm; P = 0.002) and waist (-2.9 ± 6 vs -0.6 ± 5 cm; P = 0.05); and, experienced a greater increase in peak aerobic capacity than participants in the MRP group. During the 24-week maintenance phase, participants in the SDE group maintained greater moderate and vigorous physical activity levels, weight loss, fat loss, and saw greater improvement in maximal aerobic capacity and strength.

Conclusions: In sedentary and obese women, an SDE-based program appears to be more efficacious in promoting and maintaining weight loss and improvements in markers of health and fitness compared to an MRP type program with encouragement to increase physical activity.