This study explores the role of autonomous motivation in weight loss and weight-loss maintenance among severely obese patients participating in a 6-month, very-low-calorie weight-loss program. Using self-determination theory, the researchers hypothesized that autonomous motivation—driven by internal values and personal goals—would lead to greater weight loss and better long-term maintenance compared to controlled motivation, which is driven by external pressures or rewards. The study involved 128 participants, with follow-up assessments at 23 months. Participants who had more autonomous motivation for weight loss were more likely to attend program meetings regularly, lose more weight during the program, and maintain weight loss at the 23-month follow-up. Autonomous motivation was predicted by individual differences in autonomy orientation (as measured by the General Causality Orientations Scale) and by the perceived autonomy supportiveness of the health-care staff (as measured by the Health Care Climate Questionnaire). The study found that autonomous motivation was a significant predictor of weight loss and maintenance, while the health locus of control (HLOC) did not show significant predictive power for weight loss or maintenance. The results support the idea that internal, self-directed motivation is more effective for long-term weight loss success than external or controlled motivation. The study also highlights the importance of the interpersonal climate created by health-care staff in fostering autonomous motivation among patients. The findings suggest that weight-loss programs should focus on promoting autonomous motivation through supportive, autonomy-supportive environments. This approach can enhance patient engagement, weight loss, and long-term maintenance of weight loss. The study underscores the importance of understanding and fostering intrinsic motivation in weight-loss interventions.This study explores the role of autonomous motivation in weight loss and weight-loss maintenance among severely obese patients participating in a 6-month, very-low-calorie weight-loss program. Using self-determination theory, the researchers hypothesized that autonomous motivation—driven by internal values and personal goals—would lead to greater weight loss and better long-term maintenance compared to controlled motivation, which is driven by external pressures or rewards. The study involved 128 participants, with follow-up assessments at 23 months. Participants who had more autonomous motivation for weight loss were more likely to attend program meetings regularly, lose more weight during the program, and maintain weight loss at the 23-month follow-up. Autonomous motivation was predicted by individual differences in autonomy orientation (as measured by the General Causality Orientations Scale) and by the perceived autonomy supportiveness of the health-care staff (as measured by the Health Care Climate Questionnaire). The study found that autonomous motivation was a significant predictor of weight loss and maintenance, while the health locus of control (HLOC) did not show significant predictive power for weight loss or maintenance. The results support the idea that internal, self-directed motivation is more effective for long-term weight loss success than external or controlled motivation. The study also highlights the importance of the interpersonal climate created by health-care staff in fostering autonomous motivation among patients. The findings suggest that weight-loss programs should focus on promoting autonomous motivation through supportive, autonomy-supportive environments. This approach can enhance patient engagement, weight loss, and long-term maintenance of weight loss. The study underscores the importance of understanding and fostering intrinsic motivation in weight-loss interventions.