Yale's course on food, taught by psychologist Kelly Brownell, examines eating from three angles at once: the biology of appetite and metabolism, the psychology of taste and habit, and the political and economic forces that shape what ends up on a plate. This session, the third in the series, continues the course's project of treating food choice as a problem no single discipline can explain alone, moving between physiological mechanisms like hunger regulation and the industry and policy decisions that structure the modern food environment. Brownell lectures in a straightforward classroom format, building the case that obesity and diet-related illness are not simply failures of willpower but outcomes of systems designed around cheap calories and constant marketing. The lecture fits into a semester-long argument connecting individual eating behavior to public health policy.