Economic Contextual Factors and Child Body Mass Index

This policy paper is from a series published by the National Bureau of Economic Research on obesity in the United States. The authors examined the relationship between children’s weight and fast food and fruit and vegetable prices, and children’s weight and availability of fast-food restaurants, full-service restaurants, supermarkets, grocery stores and convenience stores. Data from the Child Development Supplement of the Panel Study of Income Dynamics were combined with external food prices and density of outlets by zip code. Obesity in children has tripled in the United States in the past three decades, and by 2006 reached 12.4 percent, 17.0 percent and 17.6 percent among children aged 2–5, 6–11, and 12–19 years, respectively.

The authors found that higher prices of fruits and vegetables had a statistically significant positive effect on children’s BMI: a one-dollar increase in the price of fruit and vegetables was associated with a 20.28 percentage point increase in BMI percentile. Effects were highest among children of low-socioeconomic status (SES). The price of fast food was negatively associated with children’s BMI in the cross-sectional model, but the association did not reach statistical significance. Similarly, availability of different types of food outlets was not generally significantly associated with children’s BMI, although greater availability of supermarkets had a small, but statistically significant, negative effect on the weight of low-SES children.

These results indicate that subsidies of healthier foods targeted directly to consumers—rather than through federal programs such as Food Stamps, the Women, Infant and Children Nutrition Program, the Child and Adult Care Food Program, and the National School Lunch and Breakfast Program—may have beneficial results. Further research on pilot programs that subsidize healthy foods, and studies that examine the relationship between food taxes and energy intake and weight outcomes, will be helpful in devising pricing policies aimed at curbing the obesity crisis among children and adolescents in the United States.

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