This chapter reviews a growing body of international research that documents a puzzling pattern of gender differences in health and considers the limitations of current explanations. Such limitations derive from a failure to capture the complexity of men's and women's lives because much of the research focuses either on differences in their social and economic status or biology. We argue that an integrated model is needed to enable researchers to understand more fully the health connections between gendered lives and physiological processes. We elaborate the framework of constrained choice (CC) as one approach to address this conundrum. Constrained choice provides an innovative multilevel model for examining how the social environment differentially shapes men's and women's agency and health-related opportunities and choices. We provide examples of studies in the United States and Qatar that employ the framework and highlight ways in which it can be used more effectively in future research.