This report provides a critical analysis of obesity through the lens of health psychology and behavior change principles. It begins with an introduction that outlines the scope of the report, focusing on a scenario involving obesity within a lower-income family in the United States. The report then applies the biopsychosocial model to understand the multifaceted nature of obesity, considering biological, psychological, and social factors. It explores health psychology theories, particularly the Health Belief Model and Social Cognitive Theory, to explain health behavior change. The report identifies and explores potential interventions, including brief interventions and motivational interviewing, and discusses contextual, environmental, and political factors impacting health behaviors and sustainability. The report concludes by discussing the strengths and limitations of the interventions, providing a comprehensive overview of the topic.