Objective: The present study investigated the influence of exercise-specific motivation and volition on weight loss maintenance following an intensive lifestyle intervention (ILI).

Method: The study participants were 164 individuals with obesity (body mass index [BMI] > 30 kg/m²) that participated in an ILI. Participants' exercise-specific volition and motivation were assessed before and after the intervention as well as 3 and 12 months after completion. Volition was measured with the Volition in Exercise Questionnaire and motivation was measured with the context translated Sport Motivation Scale.

Results: Mixed model analysis revealed that when adjusting for gender, age, and education, the 6 volitional scales and intrinsic motivation predicted BMI across the 4 time points, whereas 6 volitional scales and 2 extrinsic regulation scales showed a time interaction. Backward elimination multiple mixed model analysis revealed that Volitional Inhibition - Postponing Training and Volitional Facilitation - Self- Confidence predicted BMI development, whereas Volitional Inhibition - Unrelated Thoughts, Identified Regulation, and Introjected Regulation showed a time interaction above and beyond the other scales.

Conclusion: Exercise-specific volition and motivation influence weight loss maintenance following an ILI. Volitional self-confidence and the tendency to postpone training are of importance above and beyond the previously identified predictor of autonomous exercise motivation. Results of the study also indicate that extrinsic motivation can be either facilitating or counterproductive depending on the level of self-determination.