Children and adolescents who consistently watch television for 2 hours or more a day are at an increased risk of being overweight

Children and adolescents who consistently watch television for 2 hours or more a day are at an increased risk of being overweight, to smoke, and to have high cholesterol concentrations in early adulthood—substantial risk factors for long-term health problems in later life—conclude authors of a study from New Zealand in this week’s issue of THE LANCET.

Previous research has identified associations between television viewing and poor health outcomes such as high cholesterol and obesity; no longitudinal study has assessed these effects into adulthood. Robert Hancox (University of Otago, New Zealand) and colleagues studied around 1000 children born in Dunedin, New Zealand, in 1972–73 who were followed up at numerous intervals to age 26 years. During this time parents (for children aged 5–11 years) and adolescents (aged 13 years and over) provided details of the duration of weekly television viewing. Body-mass index (BMI), blood pressure, cholesterol concentration, and cardiovascular fitness was assessed at 26 years of age.

A clear association was found between extensive television viewing (more than 2 hours a day) among children and adolescents and increased BMI, raised cholesterol, greater proportion of smoking, and poor cardiovascular fitness at age 26 years; no association was found between television viewing and blood pressure. These associations remained after adjustment for potential confounding factors such as childhood socioeconomic status, BMI at age 5 years, parental BMI, parental smoking, and physical activity at age 15 years. The investigators estimate that among all 26-year-olds, 17% of overweight, 15% of raised blood cholesterol, 17% of smoking, and 15% of poor fitness can be attributed to watching television for more than 2 hours a day during childhood and adolescence.

Dr Hancox comments: “Although the adult health indicators that we have found to be associated with child and adolescent television viewing are unlikely to result in clinical health problems by the age of 26 years, they are well established risk factors for cardiovascular illness and death later in life. Our results suggest that excessive television viewing in young people is likely to have far-reaching consequences for adult health. We concur with the American Academy of Pediatrics that parents should limit children’s viewing to 1–2 hours per day; in fact, data suggest that less than 1 hour a day would be even better. Although parents might find this difficult to maintain, lifestyle modifications in adulthood to reverse overweight, poor fitness, high blood cholesterol, and smoking are also notoriously difficult to achieve. Parents will need support and encouragement at an individual, community, and societal level. Adults are likely to obtain health benefits themselves if they lead by example and turn off the television. We believe that reducing television viewing should become a population health priority”.

In an accompanying commentary (p 226), David Ludwig (Harvard Medical School, Boston, USA) concludes: “…the data presented by Hancox and colleagues strengthen the case for a ban on food advertisements aimed at children. The argument for action is based not only on strong scientific evidence, but also on common sense. In an era when childhood obesity has reached crisis proportions, the commercial food industry has no business telling toddlers to consume fast food, soft drinks, and high-calorie low-quality snacks, all products linked to excessive weight gain. Indeed, the American Academy of Pediatrics has stated that advertising directed to young children is inherently deceptive and exploitative. A precedent for restrictions on the marketing of products deemed harmful to children already exists—tobacco. Clearly, obesity is a complex condition with numerous genetic, environmental, and psychosocial contributing factors. However, the multifactorial nature of the problem should not be an excuse for inaction. Measures to limit television viewing in childhood and ban food advertisements aimed at children are warranted, before another generation is programmed to become obese.”