Molly Jacobs*
Objectives: Weight trends established in adolescence continue through adulthood. What causes the overweight onset? The first objective of this study is to determine factors that are important in BMI determination. The second objective is to determine if those same factors influence BMI growth. The final objective determines if biological and non-biological mothers impact BMI differently.
Design: Using a longitudinal panel, I determine those factors deterministic in BMI levels in 1997 and in 2011. Then I show the relative importance of household, geographic, environment and genetic factors in BMI growth. I disaggregate the important of maternal nurture and nature using two different model specifications–a pooled model with dummy variables and a disaggregated analysis separating household by the biological status of the maternal figure.
Setting: The National Longitudinal Survey of Youth 1997 consists of a nationally representative sample of approximately 9,000 youths. In Round 1 of the survey both the eligible youth and one of that youth’s parents are interviewed, then youths are interviewed annually.
Subjects: A panel of American age 12-17 in the first year of the panel and age 27 to 32 in the final year.
Results: Results suggest that those factors playing a significant role in BMI determination at the beginning of the panel are the same at the end. Maternal BMI, previous BMI level and age are deterministic. Lack of significance in the non-biological dummy and interaction term suggests that nurturing is more deterministic than genetics. However, when the sample is disaggregated by maternal status, the impact of non-biological mothers diminishes slightly particularly at older ages.
Conclusion: Analysis suggests large racial, ethnic and gender differences in BMI growth. Minorities have faster growth. The impact of maternal BMI on youth BMI growth is present, but the strength of the relationship varies by age and model specification.