This study quantifies age-specific and lifetime costs for overweight (BMI: 25-29.9), obese I (BMI: 30-34.9), and obese II/III (BMI: >35) adults separately by race/gender strata. We use these results to demonstrate why private sector firms are likely to underinvest in obesity prevention efforts. Not only does the existence of Medicare reduce the economic burden that obesity imposes on private payers, but, from the perspective of a 20-year-old obese adult, the short-term costs of obesity are small. This suggests that legislation that subsidizes wellness programs and/or mandates coverage for obesity treatments might make all firms better off. Ironically, Medicare has a greater incentive to prevent obesity because when an obese 65 year old enters the program, his/her costs are immediate and higher than costs for normal weight individuals.