Television and Childhood Obesity

Introduction

Childhood obesity has more than tripled in the past 30 years. Although causes are multi-factorial, television viewing has been consistently associated cross-sectionally, longitudinally, and in intervention studies to childhood obesity. The mediators explaining these relationships include increased calorie intake and poorer dietary quality, and to a lesser extent, reduced physical activity. Sophisticated marketing of high fat, high sugar, high calorie foods and beverages is increasingly being targeted to children and adolescents (Gortmaker et al, pp. 356-362).

These advertisements have been shown to affect children's preferences, requests, and short-term consumption of foods and beverages. Foods eaten as snacks or as meals while viewing television tend to be higher in fat and calories, and are less likely to include fruits, vegetables or dairy products, which are also the foods least likely to be advertised. Surveys find that television sets in children's bedrooms have been increasing, so that now some 50% to 70% of youth have a bedroom television set. They view more hours of television than those without a television in the bedroom and their viewing is underestimated and often not monitored by parents. Classroom curricula and focused parental efforts to reduce and limit children's television viewing can lead to decreased viewing, which in some cases has been associated with decreased obesity. Efforts to separate snacking or eating while watching television may also be beneficial.

Television viewing and obesity

More than 20 years ago, Dietz and Gortmaker identified an association between the amount of time spent watching television and obesity among children aged 12-17 years. In a large cross-sectional study of teenagers, they demonstrated a dose-response relationship, with a 2% increase in the prevalence of obesity for each additional hour per day of television viewing (Dietz and Gortmaker, pp. 807-812). Among preschool children, Dennison and colleagues also noted a cross-sectional association between the amount of time spent watching television and the prevalence of obesity. Each additional hour per week of television viewing was associated with a 6% increase in the prevalence of obesity. A number of additional cross-sectional studies support a link between television viewing and increased risk of becoming overweight. One large national study estimated that as much as 60% of obesity incidence among children and adolescents could be attributed to excess television viewing. A prospective study of children followed from preschool through age 11 years found that body fatness increased with increasing hours of television viewing. Sedentary behavior and high fat diets appeared to strengthen the effect; thus those children who were already at increased risk were affected disproportionately (Gortmaker et al, pp. 356-362). Excess TV viewing prospectively increased the risk of overweight among a group of girls followed from 7-11 years of age. Girls who viewed more than 2 h per day of television were nearly 5 times as likely to become overweight by age 11 than girls who viewed fewer hours (Dietz, pp. 807-812).

Television in the bedroom

A number of studies have found that children with a television set in their bedrooms watch more hours per ...