Extended Theory of Planned Behavior on Eating and Physical Activity.

The evidence for Theory of Planned Behavior (TPB) on explaining weight-reduction behaviors (healthy eating [HE] and physical activity [PA]) is inconsistent. Meanwhile, research has acknowledged that the role of weight-related self-stigma may influence HE and PA engagement. We proposed and evaluated an extended TPB model incorporating weight-related self-stigma. Through convenience sampling, we assessed the TPB factors of university students with overweight (65 men and 39 women). The students completed several questionnaires assessing subjective norms (from normative beliefs), attitudes, perceived behavioral control (from control beliefs), and behavioral intentions (on HE and PA). They also responded to questions regarding their weight-related self-stigma, HE (measured using a questionnaire on maladaptive eating behaviors), and PA. The extended TPB partially explained HE and PA behaviors: weight-related self-stigma was significantly and directly associated with both HE (β = 0.27; p = .001) and PA (β = -0.30; p = .006). Perceived behavioral control was only indirectly associated with PA through intention. Behavioral intention was significantly associated with PA (β = 0.26; p = .044), but not with HE (β = -0.001; p = .99). Our findings partially support the extended TPB; however, our findings should be interpreted with caution because of the poor generalizability caused by our convenience sampling method.