TEIXEIRA, PJ, SB GOING, LB HOUTKOOPER, EC CUSSLER, LL METCALFE, RM BLEW, LB SARDINHA, and TG LOHMAN. Med. Sci. Sports Exerc., Vol. 38, No. 1, pp. 179–188, 2006. This study investigated changes in psychosocial variables related to exercise, eating, and body image during a weight reduction program and evaluated their association with weight loss in middle-aged overweight and obese women up to 1 yr after intervention. The 136 participants (age, 48.1 4.4 yr; weight, 30.6 5.6 kg· m 2) who completed the 4-month lifestyle weight reduction program (86% retention), losing 6.2 4.6%(P 0.001) of their initial weight, were followed up for 12 additional months. Of these, 82% completed 16-month assessments (weight change, 5.5 7.7%, P 0.001). Psychosocial variables were assessed by validated instruments in standardized conditions at baseline and after the intervention (4 months). Compared with 4-month assessments, body weight did not change at 16 months (P 0.09). Changes in eating restraint, disinhibition, and hunger; exercise, self-efficacy, and intrinsic motivation; body shape concerns; and physical self-worth were associated with weight change at 4 months (P 0.001, except hunger, P 0.05). Baseline-adjusted 4-month scores in all psychosocial variables also predicted weight change from baseline to 16 months (P 0.01), except hunger (P 0.05). After controlling for 4-month weight change and other covariates, increases in exercise intrinsic motivation remained predictive of weight loss at 16 months (P 0.05). Multiple linear regression showed that eating variables were significant and independent correlates of short-term weight change, whereas changes in exercise variables were stronger predictors of longer term weight outcomes. Results highlight the importance of cognitive processes during weight control and support the notion that initial focus on diet is associated with short-term weight loss, while change in exercise-related motivational factors, with a special emphasis on intrinsic sources of motivation (eg, interest and enjoyment in exercise), play a more important role in longer term weight management.