Abstract
Changing health-related behaviors requires two separate processes that involve motivation and volition, respectively. First, an intention to change is developed, in part on the basis of self-beliefs. Second, the change must be planned, initiated, and maintained, and relapses must be managed; self-regulation plays a critical role in these processes. Social-cognition models of health behavior change address these two processes. One such model, the health action process approach, is explicitly based on the assumption that two distinct phases need to be studied longitudinally, one phase that leads to a behavioral intention and another that leads to the actual behavior. Particular social-cognitive variables may play different roles in the two stages; perceived self-efficacy is the only predictor that seems to be equally important in the two phases.