Are mandatory aerobics classes in your future? "When anyone dies at an early age from a preventable cause in New York City, it's my fault," New York City Health Commissioner Thomas Frieden declared recently (Financial Times registration required). In his campaign to make sure that no New Yorker dies before his or her time, Frieden has adopted an expansive notion of public health. Historically, public health has focused on protecting people from the risks of communicable diseases. Thus public health officials have been empowered to mandate vaccinations, require the chlorination of water, order that milk be pasteurized, and quarantine sick...