Mediators of weight loss and weight loss maintenance in middle-aged women

Abstract

Long-term behavioral self-regulation is the hallmark of successful weight control. We tested mediators of weight loss and weight loss maintenance in middle-aged women who participated in a randomized controlled 12-month weight management intervention. Overweight and obese women (N = 225, BMI = 31.3 4.1kg/m 2) were randomly assigned to a control or a 1-year group intervention designed to promote autonomous self-regulation of body weight. Key exercise, eating behavior, and body image variables were assessed before and after the program, and tested as mediators of weight loss (12 months, 86% retention) and weight loss maintenance (24 months, 81% retention). Multiple mediation was employed and an intention-to-treat analysis conducted. Treatment effects were observed for all putative mediators (Effect size: 0.32-0.79, P <0.01 vs. controls). Weight change was 7.3 5.9% (12-month) and 5.5 5.0% (24-month) in the intervention group and 1.7 5.0% and 2.2 7.5% in controls. Change in most psychosocial variables was associated with 12-month weight change, but only flexible cognitive restraint (P <0.01), disinhibition (P <0.05), exercise self-efficacy (P 0.001), exercise intrinsic motivation (P <0.01), and body dissatisfaction (P 0.05) predicted 24-month weight change. Lower emotional eating, increased flexible cognitive restraint, and fewer exercise barriers mediated 12-month weight loss (R 2 = 0.31, P< 0.001; effect ratio: 0.37), but only flexible restraint and exercise self-efficacy mediated 24-month weight loss (R 2 = 0.17, P< 0.001; effect ratio: 0.89). This is the first study to evaluate self-regulation mediators of weight loss and 2-year weight loss maintenance, in a large sample of overweight women. Results show that lowering emotional eating and adopting a flexible dietary restraint pattern are critical for sustained weight loss. For long-term success, interventions must also be effective in promoting exercise intrinsic motivation and self-efficacy. © 2009 The Obesity Society.