We provide comparable evidence on the patterns and trends in obesity across the Atlantic and analyse whether there are economic rationales for public intervention to control obesity. We take into account equity issues as well as efficiency considerations, which are organized around three categories of market failures: productive inefficiencies, lack of information or rationality and health insurance externalities. We also calculate the long term financial consequences of current US and European obesity trends, and conclude with a brief review of current policies to reduce and prevent excessive body weight both in Europe and the US.