Essays on childhood obesity

This dissertation consists of three essays on childhood obesity. The first essay, “What Money Can Buy: Family Income and Childhood Obesity” investigates the relationship between family income and childhood obesity using the Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 (ECLS-K). In this essay I report three new findings. First, family income and childhood obesity are negatively correlated overall but among children from very low-income families they are positively correlated. Second, the negative association between family income and Body Mass Index (BMI) is especially strong and significant among high-BMI children. Third, the gap in obesity rates between children from low- and high-income families increases as children age. I further investigate potential factors that might contribute to a rapid increase in obesity rates among low-income children. I find that their faster weight gain, rather than their slower height growth, is a greater contributor to rapid BMI growth over time. On the other hand, I also find that faster weight gain by low-income children cannot be attributed to any single factor, such as participation in school meal programs, parental characteristics, or individual characteristics. The findings add to the current obesity debate by demonstrating that the key to curbing childhood obesity may lie in factors generating different obesity rates across income levels. In the second essay, “Does the Earned Income Tax Credit Increase Children’s Weight? The Impact of Policy-Driven Income on Childhood Obesity”, I exploit substantial increases in the Earned Income Tax Credit (EITC) to study how a policy-driven change in family income affects childhood obesity. In contrast to a widely accepted belief, I find that income has an adverse effect on children's weight. My difference-in-difference estimates indicate that the probability of being obese increased more among children whose families experienced a greater income shock. Moreover, instrumental variable estimates demonstrate that a $1,000 increase in policy-driven income leads to a 0.5-percentage point increase in obesity rates. The finding suggests that a non-health social safety net program such as the EITC could have unintended negative side effects. In the third essay, “The Impact of Maternal Employment on Children’s Adiposity: Evidence from the China’s Labor Policy Reform”, we provide new evidence on the effect of maternal employment on childhood adiposity using the longitudinal survey data from the China Health and Nutrition Survey (CHNS). Our main identification strategy relies on the 1995 legislative change to the labor regulations in China that reduced the number of working days from six to five days a week without changing workers’ wages. While maternal employment and childhood obesity in China exhibits the same positive association as in the US, our difference-in-difference estimate presents a different picture. Comparing children whose mothers are wage earners to those whose mothers are self-employed, we find that a reduction in maternal labor supply led to children’s weight gain. Such weight gain was beneficial for those who were previously underweight but harmful to those who became overweight. Further investigation reveals that the effect is stronger among children who are male, from low-socioeconomic households, and from urban areas