LAUSR

Abstract Objective This study examines the associations between pre-to post-intervention changes in motivation and physical activity (PA) levels of bariatric patients involved in a 6-month postoperative PA program based on self-determination theory (SDT). We also explore the extent to which patients’ perception of autonomy support and basic psychological need satisfaction during the program were associated with changes in their motivation to exercise. Method Forty patients were assigned to a motivational PA intervention (MPAI-G) or to a control group (CG). Both groups completed questionnaires assessing the variables of interest and wore GT3X accelerometers before surgery and after the program. Results Thirty-two participants (78.1% female) completed all measures and were included in the present analyses. CG showed greater increases in integrated (d = −1.60, 95% CI [-2.40, - 0.81]) and identified regulation (d = −0.75, 95% CI [-1.47, −0.03]) than MPAI-G. However, the MPAI-G experienced increases in introjected regulation (d = 1.95, 95% CI [1.11, 2.79]) and greater decreases in external regulation (d = −1.00, 95% CI [-1.74, −0.27]) than CG, which were associated with decreases in sedentary activity and increases in light and total PA. Oppositely to the CG, amotivation also decreased in the MPAI-G (d = −2.98, 95% CI [-3.98, −1.97]) and it was related to increases in light and total PA. Changes in exercise motivation were associated with perceived autonomy support and basic psychological need satisfaction during the program. Conclusion The SDT-based PA program gave rise to greater changes in controlled forms of motivation and amotivation than in autonomous motivation in post-bariatric surgery patients.