Prevalance of morbid obesity and metabolic syndrome in U.S. adolescents and very young adults

Purpose The WHO body mass index (BMI) classes were developed primarily on an older adult population and may not adequately reflect increases in metabolic risk for a younger population. The purpose of this analysis was to estimate the numbers of adolescents and very young adults within adult obesity classes and to assess metabolic risk by obesity class and age in 5-year increments. Methods We used SUDAAN and data from NHANES 1999–2002 to estimate the prevalence in the United States of adolescents (ages 13–17) and very young adults (ages 18–22) who fell into adult WHO obesity classes I (BMI 30–34.9), II (35–39.9) and III (>40, also called morbid obesity). We used the Adult Treatment Plan III criteria to define individuals as having metabolic syndrome if they had at least three of the following: impaired fasting glucose, abdominal obesity, high triglycerides, low HDL or hypertension. Results We estimate that 190,185 or 1% of U.S. adolescents and 552,547 or 3% of very young adults are in adult obesity class III. An additional 590,495 (6%) adolescents and 775,903 (4%) very young adults are in adult obesity class II. While the entire NHANES 1999–2002 population shows the expected increase in the prevalence of metabolic syndrome as obesity and age increase (p < 0.0001) this dose response is not evident in adolescents and very young adults (classes II and III), all of whom had virtually identical risks of adult metabolic syndrome (42%–44%). This equates to 2.1 million individuals between the ages of 13 and 22 years old who already have adult metabolic syndrome. Conclusion Over four million U.S. adolescents and very young adults have an obesity level that significantly increases their risk of morbidity and mortality from metabolic syndrome. The risk of metabolic syndrome in these young people is equal to that of the population aged 58 to 62 and higher than any normal weight group including those over 68 years old.