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In light of the well-documented health benefits of physical activity and the fact that the majority of adult men and women are inactive, promoting regular physical activity is a public health priority. This chapter reviews current research findings regarding the determinants of exercise behavior. It also discusses the implications of this knowledge for individual and public health recommendations and intervention strategies for promoting physical activity. The discussion is predicated on the belief that physical activity is a complex, dynamic process. During their lives, individuals typically move through various phases of exercise participation that are determined by diverse factors. This chapter discusses physical activity determinants in two broad categories: individual characteristics, including motivations, self-efficacy, exercise history, skills, and other health behaviors; and environmental characteristics such as access, cost, and time barriers and social and cultural supports.

Background Gastric bypass has profound effects on glycemic control in adults with type 2 diabetes mellitus. The goal of this study was to examine the long-term rates and clinical predictors of diabetes remission and relapse among patients undergoing gastric bypass. Methods We conducted a retrospective cohort study of adults with uncontrolled or medication-controlled type 2 diabetes who underwent gastric bypass from 1995 to 2008 in three integrated health care delivery systems in the United States. Remission and relapse events were defined by diabetes medication use and clinical laboratory measures of glycemic control. Results We identified 4,434 adults with uncontrolled or medication-controlled type 2 diabetes who had gastric bypass. Overall, 68.2% (95% CI: 66%, 70%) experienced an initial complete diabetes remission within five years after surgery. Among these, 35.1% (95% CI: 32%, 38%) redeveloped diabetes within five years. The median duration of remission was 8.3 years. Significant predictors of complete remission and relapse were poor preoperative glycemic control, insulin use, and longer diabetes duration. Weight trajectories after surgery were significantly different for never remitters, relapsers, and durable remitters (p=0.03). Conclusions Gastric bypass surgery is associated with durable remission of type 2 diabetes in many but not all severely obese diabetic adults, and about one-third experience a relapse within five years of initial remission. More research is needed to understand the mechanisms of diabetes relapse, the optimal timing of surgery in effecting a durable remission, and the relationship between remission duration and incident microvascular and macrovascular events.

The management of many health disorders often entails a sequential, individualized approach whereby treatment is adapted and readapted over time in response to the specific needs and evolving status of the individual. Adaptive interventions provide one way to operationalize the strategies (e.g., continue, augment, switch, step-down) leading to individualized sequences of treatment. Often, a wide variety of critical questions must be answered when developing a highquality adaptive intervention. Yet, there is often insufficient empirical evidence or theoretical basis to address these questions. The Sequential Multiple Assignment Randomized Trial (SMART)-a type of research design-was developed explicitly for the purpose of building optimal adaptive interventions by providing answers to such questions. Despite increasing popularity, SMARTs remain relatively new to intervention scientists. This manuscript provides an introduction to adaptive interventions and SMARTs. We discuss SMART design considerations, including common primary and secondary aims. For illustration, we discuss the development of an adaptive intervention for optimizing weight loss among adult individuals who are overweight. KEYWORDS