In a new study just published in the New England Journal of Medicine, Dr. S.A. Cunningham of Emory University and colleagues reported that later incidence (new cases) of obesity is greater for children who are overweight as early as kindergarten. Gina Kolata also covered this research in The New York Times.
The data they analyzed came from the Early Childhood Longitudinal Study, run by the Department of Education, which followed over 9,000 children who started kindergarten in the fall of 1998 (average age was about 5 1/2 years) until 2007 when they were approximately 14 years old. Children were also examined at ages 6, 7, 9, 11 and 14 years of age, at which times their heights and weights were measured. If a child’s BMI was greater than the 85th percentile for their age and sex, he or she was considered overweight, and those whose BMIs topped the 95th percentile were considered obese. The study population was chosen to be nationally representative.
The investigators calculated the prevalence of obesity in each age group as the proportion who were obese, and the incidence of obesity as the occurrence of a new case of obesity in a child who had not been obese at an earlier age. There were approximately 6800 children who were not obese in kindergarten, and thus were at risk for newly established obesity.
At the beginning of the study, 12 percent of the children were already obese, and 15 percent were overweight, and thus were considered to be at risk for incident obesity. By the final measurements at age 14, approximately 21 percent were obese, and 17 percent were overweight.
Of the new obesity cases that occurred between kindergarten and eighth grade, 45 percent were among the 15 percent who were overweight initially. On an annual basis, the incidence of obesity among those children was 20 percent, compared to 2 percent among kids who had entered kindergarten at a normal BMI. Overall, the risk of becoming obese was four-fold greater for children who had been overweight kindergartners compared to those who had been of normal weight.
In addition to the overall results, the researchers also found that the incidence of obesity tracked with socioeconomic status, with those in the highest income bracket being the least likely to become obese. Furthermore, high birthweight children were more likely to become obese than other children.
In their discussion, the authors speculate “obesity-prevention efforts that are focused on children who are overweight by the age of 5 years may be a way to target the children who are most susceptible to becoming obese during later childhood and adolescence.” Since it has been shown in numerous studies that obese adolescents often become obese adults, reducing the occurrence of obesity in young children may well be helpful in avoiding the progression to later obesity and concomitant negative health effects.
ACSH’s Dr. Ruth Kava pointed out “Among some groups, a well-padded baby or toddler is considered healthy, but these data suggest that this may not really be true. Pediatricians and other healthcare providers should become cognizant of the risk of early overweight and advise parents accordingly.”