Why are some people able to change their behavior, while others are not? This is a very important question, especially when it comes to health. We are increasingly coming to appreciate the importance of lifestyle and behavioral factors in influencing health outcomes. On this episode, I discuss theories of behavior change and the factors researchers have found are most important in driving health behavior. I discuss some popular psychological theories that have successfully been applied to health behavior. These theories include: The Health Belief Model, The Theory of Reasoned Action, The Theory of Planned Behavior, The Transtheoretical Model of Change, Social Cognitive Theory, and Ecological theories. Together, these theories form a broad picture of which psychosocial forces most impact people’s health behaviors, including their ability to change and adopt healthier habits.