Helping overweight women become more active: Need support and motivational regulations for different forms of physical activity

ObjectivesThis study analyzed mechanisms by which a one-year obesity treatment intervention based on self-determination theory (SDT) influenced physical activity level and whether motivational predictors differed for structured vs. lifestyle forms of physical activity.DesignRandomized controlled trial lasting 1-year.MethodPre-menopausal overweight and obese women (n = 239; 37.6 ± 7.1 y; 31.5 ± 4.1 kg/m2) participated in a group intervention designed to increase physical activity and motivation, following SDT. Partial least squares (PLS) latent variable modeling was used to test a cross-sectional multiple-level mediation model comprising experimentally-manipulated contextual need support, perceived need satisfaction, and motivational regulations for two distinct forms of physical activity.ResultsThe structural model explained a large amount of variance (62%) for intrinsic motivation, and moderate amounts of variance (16–25%) for the remaining regulations and exercise behaviors. Moderate and vigorous exercise was positively influenced by intrinsic motivation (p < .001) whereas lifestyle physical activity was not significantly predicted by motivational regulations. Behavioral regulations were influenced by perceived autonomy and perceived competence and both needs were affected by contextual support from treatment climate (p < .001).ConclusionsResults provide support for using the SDT framework to understand physical activity motivational processes in the context of weight management. Results also highlight structured and lifestyle physical activity as being promoted by different processes as a result of the intervention: more direct effects on lifestyle physical activity and indirect effects on structured exercise, mediated by intrinsic motivation.