"When time watching television is taken into account, the number of hours of fast food advertising per week has no significant impact on overweight."
A number of population measures suggest that childhood overweight has increased since the early 1960s. In explaining this, researchers have tended to focus on environmental factors that affect energy intake and expenditure. When energy intake is greater than energy expenditure, children gain weight. More time spent watching television or computer screens is believed to result in less time spent in physical activity, which would decrease energy expenditure. Eating more food, or food that contains more calories, increases energy intake. Since the 1950s, fast food restaurants have offered convenient, reasonably priced, calorie dense food that tastes good. Their growing popularity has led some researchers to ask whether their existence contributes to childhood overweight.
In Fast-Food Restaurant Advertising on Television and its Influence on Childhood Obesity (NBER Working Paper No. 11879), Shin-Yi Chou, Inas Rashad, and Michael Grossman use data from an advertising tracking service and two surveys to estimate the effect of fast food advertising on the weight of individual children. They take into account the number of hours of advertising by fast food restaurants on local broadcast television, each child's age, race, gender, and the number of hours of television watched each week, household income, whether the child's mother is overweight, and her employment status. Also included are variables for the state in which the child lives, including the per capita number of fast-food and full-service restaurants, the inflation-adjusted price of legally sold cigarettes, the existence of smoking bans, and the inflation-adjusted price of food prepared at home and purchased from full service and fast-food restaurants.
When time watching television is taken into account, the number of hours of fast food advertising per week has no significant impact on overweight for either children aged 3-11 or teenagers aged 12-18. When time television watching is excluded, then "advertising messages seen significantly increase a child's probability of being overweight." The authors find that a half hour increase in advertising in a week increases the probability of being overweight by 1.6 percentage points for boys, and by 1.1 percentage points for girls aged 3-11. For teenagers, the probability of being overweight increases by 3.2 percentage points for girls and 0.6 percentage points for boys. In terms of body mass index (BMI), an additional half hour of advertising is estimated to increase a boy's body mass index by 2 percent and a girl's body mass by 1 percent.
For 3-11 year olds, BMI increases with age, but the probability of being overweight decreases. Hispanic boys and Black girls are more likely to be overweight. Children from higher income families are significantly less likely to be overweight. Mother's weight is a "strong predictor of a child's body mass index and the probability of being overweight." For teenagers, mother's weight is "strongly associated" with the probability of being overweight as is "being a black female."
The authors discuss several policy options for limiting fast food advertising including banning it and eliminating it as a tax-deductible business expense. Based on their results, eliminating deductibility would increase advertising costs by 54 percent and reduce the number of overweight children and adolescents by 5 and 3 percent respectively
-- Linda Gorman