Objective: To investigate whether TV viewing more than recommended thresholds (<2 hours/day) in early childhood is associated with trajectories of overweight and obesity (OW/OB). Methods: Participants from the 1970 British Cohort Study with complete BMI data at age 10, 26-30, 34 and 42 years (n=4174; 2392 females) were selected and their BMI classified according to the International Obesity Task Force cut-points. Trajectories of OW/OB were categorised as: "never OW/OB", "mid-adulthood onset" (OW/OB at 42 years only), "early adulthood onset" (OW/OB from 26, 30, or 34 years), "always OW/OB", and "other". Of those selected participants, 3347 (1926 females) had information on TV viewing at 5 years and were included for analysis. Multinomial logistic regression was used to assess associations between excessive TV viewing (≥2 hours/day) and trajectories of OW/OB (outcome). Results: More boys watched TV for ≥2 hours/day at 5 years than girls (32.3% versus 28.3%; p=0.01). Excessive TV viewing significantly increased the risk of being always OW/OB both in males (relative risk ratio=2.52; 95% confidence interval: 1.50-4.24) and females (1.74; 1.16-2.61), and of early adulthood onset in females (1.39; 1.10-1.75), compared to never being OW/OB in unadjusted analyses (all p<0.01). The increased risk of being always OW/OB remained significant for males (2.45; 1.40-4.29; p=0.002) but not females (1.37; 0.89-2.12; p=0.15) when adjusted for childhood socioeconomic status, maternal education and maternal BMI in childhood. Conclusions: Excessive early childhood TV viewing is associated with unhealthy later weight trajectories and likely represents an important preventive opportunity that requires further study
