Annual incidence and prevalence of obesity in childhood and young adulthood based on a 30-year longitudinal population-based cohort study in Korea: the Kangwha study

Purpose: Childhood obesity is a major global issue that causes a variety of health problems and high social costs. Many previous studies have investigated childhood obesity using cross-sectional data, but few longitudinal cohort studies have been performed, especially in the Korean population. Methods: We analyzed the incidence and prevalence of obesity and overweight in a Korean prospective cohort study of children that were followed-up from age 7 to age 36. The study eventually recruited a total of 1216 participants, with 16 follow-up surveys over 30 years (1986–2017). Results: The annual incidence of obesity showed a small peak (2.1%) at age 13 when the cohort entered middle school, but a rapid increase (6.4%) when participants reached the age of 20. The prevalence of obesity and overweight at age 8 was 0.8% and 0.9%, respectively, and increased rapidly from age 12 (obesity 2.2%, overweight 4.6%), reaching 9.5% and 15.9%, respectively, at age 20. The prevalence of obesity and overweight was consistently higher in girls than in boys during the childhood period, but this trend reversed in adulthood. Conclusions: Incidence and prevalence of obesity and overweight increased markedly after the final grades of elementary school in females, but after adolescence in males.