OBJECTIVE To test whether TV use has both concurrent effects on body mass index (BMI) at the time of survey interviews and long-term, enduring effects via the promotion of future levels of TV use. METHODS Two waves of survey data from the Panel Study of Income Dynamics were used to test relationships between TV use and BMI among a nationally representative sample of children and their parents (n = 1,421). Path analysis was used to model effects of childhood (1997) levels of TV use and BMI on the same variables 14 years later (2011). RESULTS Path analysis showed childhood TV use was associated positively with childhood BMI (β = 0.08, P < 0.05), and young adult TV use was related positively to young adult BMI (β = 0.10, P < 0.01). Heavy childhood TV use also persisted into young adulthood (β = 0.15, P < 0.001), indirectly increasing young adult BMI (β = 0.02, P < 0.05). CONCLUSIONS Heavy childhood TV users tend to become heavy young adult users. The continuation of TV behavior from childhood to young adulthood independently increases BMI.