The worldwide association between television viewing and obesity in children and adolescents: cross sectional study

Abstract

Background: Studies exploring the effect of television viewing on obesity throughout childhood are conflicting. Most studies have been confined to single high-income countries. Our aim was to examine the association between television viewing habits and Body Mass Index (BMI) in adolescents and children in a multicentre worldwide sample.

Methods: In the International Study of Asthma and Allergies in Children Phase Three, adolescents aged between 12 and 15 years completed questionnaires which included questions on television viewing habits, height and weight. Parents/guardians of children aged between 5 and 8 years completed the same questionnaire on behalf of their children. The questionnaire asked "During a normal week, how many hours a day (24 hours) do you (does your child) watch television?" Responses were categorised as; "short" (<1 hour), "moderate" (1 to ≤3 hours), "long" (3 to ≤5 hours) and "prolonged" (>5 hours).

Findings: 207,672 adolescents from 37 countries and 77,003 children from 18 countries provided data. Daily television viewing in excess of one hour was reported in 89% of adolescents and 79% of children. Compared with adolescents in the short viewing group, those in the moderate, long and prolonged groups had BMIs that were 0.14 kg/m(2), 0.21 kg/m(2), 0.30 kg/m(2) and 0.08 kg/m(2), 0.16 kg/m(2) and 0.17 kg/m(2) larger for females and males respectively (both P<0.001). Compared with children in the short viewing group, those in the moderate, long and prolonged groups had BMIs that were 0.24 kg/m(2), 0.34 kg/m(2), 0.36 kg/m(2) and 0.19 kg/m(2), 0.32 kg/m(2) and 0.36 kg/m(2) larger for females and males respectively (both P<0.001).

Interpretation: Increased television viewing hours were positively associated with BMI in both adolescents and children with an apparent dose response effect. These findings extend the evidence that television viewing contributes to increased BMI in childhood.

Figure 1. Flow of subjects through study. Panel A shows the flow of adolescents and Panel B shows the flow of children.

Figure 2. Daily television viewing of subjects by country presented as percent in long and prolonged categories.

Panel A shows adolescent television viewing and Panel B shows television viewing of children.

Figure 3. BMI of subjects by country presented as percent of subjects in overweight and obese categories.

Panel A shows the BMI of adolescents and Panel B shows the BMI of children.

Figure 4. Association between average daily television viewing hours and subject BMI by centre.

The difference in BMI (Kg/m²) between subjects with long and prolonged viewing hours and those with short and moderate viewing hours in each country by centre (positive difference represents an association of higher viewing time with higher BMI). Panel A shows the association in adolescents and Panel B shows the association in children. For each country the proportion of subjects who view television for more than three hours per day on average (long and prolonged categories combined) is shown in parentheses. Those centres with reported height and weights are shown with filled in circles, and those centres that measured heights and weights are shown with hollowed circles.