There exists enormous variation in estimates of the lifetime cost of obesity by race. In order to justify policy measures to reduce obesity rates nationally, we must first discern the cost of doing nothing, so this question remains imperative and unresolved. Although several researchers have sought to quantify obesity’s true cost stratified by race, none have produced a race-specific age-related weight gain curve, a vital component in producing an accurate estimate. This paper employs a Markov model of BMI category state changes separately for black and white males and females from ages 18 to 75 applied to updated estimates of obesity’s costs and effect on mortality to quantify the median lifetime cost of obesity at age 18. It finds lower lifetime costs than previously, due largely to the staggering gain in weight among normal weight individuals, particularly among black males, that occurs in early adulthood.