Individuals with severe obesity (body mass index [BMI] ≥40) encounter serious and potentially life-threatening complications, including diabetes, hypertension, hyperlipidemia, asthma, and arthritis,¹ and substantial reductions in life expectancy.² Repeated cross-sectional and self-reported data suggest that severe obesity prevalence has increased substantially over the past few decades,^3-7 potentially increasing at a faster rate than moderate obesity.⁶ In 2000, an estimated 2.2% of adults,³ or 4.8 million individuals, were severely obese,^8,9 with a disproportionately higher prevalence in women and racial/ethnic minorities.^3,4,7 Yet, few national studies track individuals over time to understand the progression of obesity to severe obesity.

No longitudinal analyses using national data have evaluated the increase in obesity from adolescence into early adulthood. We examined obesity incidence, persistence, and reversal in a nationally representative cohort of US teens followed into their early 30s, using measured height and weight data, in individuals enrolled in wave II (1996; 12–21 years), wave III (2001; 17–26 years), and wave IV (2008 early release data; 24–32 years) of the National Longitudinal Study of Adolescent Health (N = 8,675). Obesity was defined as a BMI ≥95th percentile of the 2000 Centers for Disease Control/National Center for Health Statistics growth charts or ≥30 kg/m² for individuals <20 years and ≥30 kg/m² in individuals ≥20 years. In 1996, 13.3% of adolescents were obese. By 2008, obesity prevalence increased to 36.1%, and was highest among non‐Hispanic black females (54.8%). Ninety percent of the obese adolescents remained obese in 2008. While annual obesity incidence did not decline in the total sample across the two study intervals (2.3% per year 1996–2001 vs. 2.2% per year 2001–2008), rates among white females declined (2.7 to 1.9% per year) and were highest among non‐Hispanic black and Hispanic females (3.8 and 2.7% per year, 1996–2001 vs. 3.0 and 2.6% per year, 2002–2008, respectively). Obesity prevalence doubled from adolescence to the early 20s, and doubled again from the early to late 20s or early 30s, with strong tracking from adolescence into adulthood. This trend is likely to continue owing to high rates of pediatric obesity. Effective preventive and treatment efforts are critically needed.

No nationally representative longitudinal data have been analyzed to evaluate the incidence of obesity in the transition between adolescence and adulthood. The objective was to examine dynamic patterns of change in obesity among white, black, Hispanic, and Asian US teens as they transitioned to young adulthood. We used nationally representative, longitudinally measured height and weight data collected from US adolescents enrolled in wave II (1996; ages 13-20 y) and wave III (2001; 19-26 y) of the National Longitudinal Study of Adolescent Health (n = 9795). Obesity incidence was defined on the basis of International Obesity Task Force (IOTF) cutoffs (wave II), which link childhood body mass index (BMI) centiles to adult cutoffs (BMI > or = 30; wave III), for comparability between adolescence and adulthood. In addition, the more commonly used cutoff of BMI > or = 95th percentile for age- and sex-specific cutoffs from the 2000 Centers for Disease Control and Prevention growth charts for adolescents (wave II) were compared with adult cutoffs (BMI > or = 30; wave III). On the basis of the IOTF cutoffs, obesity incidence over the 5-y study period was 12.7%; 9.4% of the population remained obese and 1.6% shifted from obese to nonobese. Obesity incidence was especially high in non-Hispanic black (18.4%) females relative to white females. The prevalence of obesity increased from 10.9% in wave II to 22.1% in wave III, and extreme obesity was 4.3% at wave III on the basis of a BMI > or = 40. During a 5-y transitional period between adolescence and young adulthood, the proportion of adolescents becoming and remaining obese into adulthood was very high. This upward trend is likely to continue. Effective preventive and treatment efforts are critically needed.