Childhood Obesity: Prediction and Prevention

Abstract

Source: Cunningham SA, Kramer MR, Narayan KMV. Incidence of childhood obesity in the United States. N Engl J Med. 2014; 370(5): 403– 411; doi: 10.1056/NEJMoa1309753Investigators from Emory University sought to determine the incidence of obesity in children by evaluating data from the Early Childhood Longitudinal Study (ECLS). For the ECLS, in 1998–1999 a cohort of kindergarten children were enrolled who were considered to be representative of all kindergarten children in the United States for that school year. ECLS data included measurements of height and weight at 7 time points from kindergarten to the end of eighth grade (age 5–14 years). Additional ECLS data collected included sex, race or ethnic group, socioeconomic status, and birth weight. Using ECLS data, investigators calculated each child’s BMI and used the Centers for Disease Control and Prevention definitions for overweight (BMI 85 to <95%) and obese (BMI ≥95%).1,2 Children already obese at the time of study entry were excluded. The annual incidence of obesity was defined as a new case of obesity in a child not previously obese per year.Of the 7,738 children in the cohort, 12.4% were obese at the start of kindergarten; therefore, 6,807 were included in the analysis. The mean age was 5.6 years at entry in ECLS and 14.1 years at completion. The annual incidence of obesity was 5.4% during the kindergarten year, but decreased to 1.9% per year for boys and 1.4% per year for girls for the period from fifth to eighth grade.Among the 14.9% of kindergartners who were overweight at kindergarten entry, 31.8% became obese by age 14 compared to 7.8% of those who were of normal weight in kindergarten. A total of 45% of the incident obesity between ages 5 and 14 years occurred among this group of overweight kindergartners. A birth weight of >4 kg was associated with a 5.1-fold increased risk of becoming obese among overweight kindergartners compared to normal weight kindergartners with high birth weights. Among overweight children, high socioeconomic status and non-Hispanic white and black race/ethnicities were associated with a 5.0-, 4.4-, and 4.3-fold increased risk, respectively, of becoming obese.The investigators conclude that a substantial component of childhood obesity is established by age 5 years.Dr Fechner has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.Obesity has become a major health concern in the United States with associated morbidity and mortality. While the prevalence of obesity is well known, few studies have examined the incidence of obesity in school-aged children. This study determines the incidence of obesity in school-aged children and identifies those at greatest risk: babies who are large at birth and children who are overweight when they begin kindergarten.An important omission of this study is those kindergartners who are already obese when they enter kindergarten. Based on weight trajectories, the investigators estimated that those in kindergarten who were at 95% and 99% for BMI had a 47% and 72% probability, respectively, of still being obese at the completion of eighth grade. By excluding obese kindergartners, however, the investigators could not capture those who improved to being overweight and then later again became obese, meeting the criteria for a new case of obesity.This study provides strong data to support the hypothesis that early intervention is needed to prevent obesity. Childhood is an opportune time to teach children good eating habits and the value of exercise. Screen time, whether it is TV or computers, should be monitored. Schools, too, play an important role as they often provide 1 to 2 meals per day plus snacks for young children. Recess and physical education should be part of a child’s daily school life, as should after-school activities. As physicians, it is important for us to review growth charts with parents so that children who are gaining weight inappropriately can be identified and changes made to their lifestyle before they become overweight or obese.An editorial appearing with this article concurred that it is necessary to improve prevention efforts for those children with BMIs ≥85%.3 While clinical interventions are important, larger cost-effective policy and programmatic changes are needed. A Cochrane review of interventions for preventing obesity in children4 performed a meta-analysis of 37 studies involving 27,946 children and found evidence to support obesity prevention programs in children. However, which interventions are most beneficial still needs to be determined. While waiting for these future studies, incorporating healthy lifestyle changes into pediatric well child care visits should continue, especially in those children <5 years.