Baseline dynamics of an obesity epidemic. (A) Time-dependent and (B) age-dependent epidemiological trajectories are shown. A. The time evolution of the numbers of never-obese, obese and ex-obese individuals. As time goes by, the prevalence of obesity converges to an equilibrium level. B. Age-specific risk of obesity in a stationary state. The vertical axis represents the risk (or probability) of age a at birth (and thus, it should be noted that the proportions do not sum up to 1 due to natural mortality).