title: 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 +/- 4.1 kg/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.
authors.affiliation: Department of Exercise and Health, Faculty of Human Kinetics, Technical University of Lisbon, Lisbon, Portugal. pteixeira@fmh.utl.pt
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Teixeira
authors.forename: Marlene N
authors.initials: MN
authors.lastname: Silva
authors.forename: Sílvia R
authors.initials: SR
authors.lastname: Coutinho
authors.forename: António L
authors.initials: AL
authors.lastname: Palmeira
authors.forename: Jutta
authors.initials: J
authors.lastname: Mata
authors.forename: Paulo N
authors.initials: PN
authors.lastname: Vieira
authors.forename: Eliana V
authors.initials: EV
authors.lastname: Carraça
authors.forename: Teresa C
authors.initials: TC
authors.lastname: Santos
authors.forename: Luís B
authors.initials: LB
authors.lastname: Sardinha
mesh_terms: D000328:Adult; D001828:Body Image; D004644:Emotions; D015444:Exercise; D005247:Feeding Behavior / Q000523:psychology*; D005260:Female; D006801:Humans; D057194:Intention to Treat Analysis; D008875:Middle Aged; D009042:Motivation; D009765:Obesity / Q000523:psychology* / Q000628:therapy; D050177:Overweight / Q000523:psychology* / Q000628:therapy; D020377:Self Efficacy; D012927:Social Control, Informal; D016896:Treatment Outcome; D015431:Weight Loss