Revision with unchanged content. Obesity is an epidemic that is particularly prevalent amongst aging Ameri?cans. The economic literature concerning this phenomenon is blossoming, but largely focuses on its causes. This work examines the issue from a dif?ferent direction. First, a Bayesian model is developed to determine how aging Americans use obesity related health information, and if their response differs from the non-obese. Second, a behavioural model is employed to see if the same health information elicits a behavioural response in the form of weight loss. This is the first behavioural response model to determine the existence and magnitude of BMI defined behavioural changes after exposure to new personal obesity related risk information. This book is addressed to researchers in economics, sociology, demographics and profes?sionals in the medical arena.