Abstract MP50: The Development of Severe Obesity in Urban Girls

Abstract

Introduction: Despite rising prevalence of youth-onset severe obesity, its development is poorly understood. Hypothesis: Girls who are severely obese in early adolescence will show more rapid growth between ages 7-10 and 11-14 compared with those who have normal BMI in early adolescence. The two groups’ BMI trajectories will diverge in late childhood. Methods: To estimate the prevalence and incidence of youth-onset severe obesity (BMI >99 th percentile-for-age) and compare weight development between girls with severe obesity and those with healthy BMI. We examined data from participants in an accelerated longitudinal cohort study of urban girls from a single US city (n=2206; 51% African American). Data were collected annually from 2003-2004 (when participants were aged 7-10) to 2008-2009. Girls were excluded who became pregnant (n=143) or provided no weight data (n=102) in those six years. Prevalence data calculations were compared using the standard severe obesity definition as well as an alternative definition (120% of the 95 th BMI-percentile-for-age). We used unconditional latent growth curve models (LGCM) to compare the BMI development of girls who were severely obese at age 12-15 with those who had normal BMI at age 12-15. Results: Severe obesity prevalence was 4.5% at age 7-10 and 6.3% (3.6% of white girls and 8.2% of African American girls; p<0.001) at age 12-15. Incident severe obesity was 0% to 1.9% annually. The alternative definition of severe obesity yielded slightly higher prevalence estimates (6.2% at age 7-10 and 9.5% age 12-15). When we compared 12-15 year-old girls with severe obesity versus healthy BMI, average body weight was already distinct 5 years earlier [16.5 kg (SD 2.2) versus 27.0 kg (SD 4.7)].The difference in average BMI between the two groups widened with each sample year. Unconditional latent growth curve models between ages 7-10 and 11-14 indicated an average increase of 0.59 kg/m 2 annually in the healthy BMI group and 2.32 kg/m 2 annually in the severe obesity group. Conclusions: Severe obesity was relatively common in urban girls, particularly African American girls, by age 7-10. Girls with severe obesity showed a nearly 4-fold rate of BMI change over 5 years, compared to girls with healthy BMI. Girls with early adolescent severe obesity already showed significantly higher BMI by age 7-10. Prevention is essential prior to age 7, with emphasis on minority populations.