More than half of U.S. children will be obese at age 35, according to a study published in the New England Journal of Medicine.
Researchers used data from five nationally representative studies with repeated height and weight measures of 41,567 children and adults, with an average of 4.3 measurements taken per person. They then simulated growth trajectories across the life course based on predictive curves developed by the Centers for Disease Control and Prevention (CDC). Secular trends in weight gain were also taken into account.
Led by Zachary J. Ward, MPH, the researchers reported 57.3 percent of today’s youth will be obese at age 35.
“Although a broad range of public health and clinical efforts appear to have stabilized early childhood obesity rates, in this study we estimated that among children between the ages of 2 and 19 years in 2016, more than half (57.3%) will be obese by the age of 35 years,” they wrote. “However, the majority of these children were not currently obese; about half of the total prevalence of obesity began in childhood, and adult-onset obesity by 35 years of age accounted for the rest.”
Body mass index (BMI) categories were calculated based on CDC standards, with obesity defined as 30 kilograms per square meter in adults. Severe obesity was defined as BMI of 35 or higher in adults and 120 percent or more of the 95th percentile in same-aged children. Severe obesity affects 4.5 million children in the U.S., a proportion of 6 percent, according to the authors.
In Ward et al.’s model, the relative risk of adult obesity increased with age. Compared to non-obese children, obese 2-year-olds demonstrated a 30 percent increased risk of having obesity at 35, while obese 19-year-olds had double the risk of adult obesity. Severely obese 19-year-olds were 3.1 times more likely to be obese at age 35.
“The persistence of elevated risk is striking: a 2-year-old who is obese is more likely to be obese at 35 years of age than an overweight 19-year-old,” Ward and colleagues wrote. “Thus, our findings highlight the importance of promoting a healthy weight throughout childhood and adulthood.”
Black and Hispanic children were most likely to become obese in the simulation model, consistent with current trends and previous research. The researchers noted “significant” racial disparities in the prevalence of obesity were already present by the age of 2.
Ward et al. said their model had lower relative risks for developing obesity than previous studies because they factored in “secular trends of an increasing risk of obesity in the reference group of children who were underweight or of normal weight.”
“We found that only those children with a current healthy weight have less than a 50% chance of becoming obese by the age of 35 years,” they wrote. “For children with severe obesity, the risk of adult obesity is particularly high.”
The simulation model relied on the assumption that, on average, people with similar trajectories in height and weight over a given period of their lives would continue to grow similarly in the future. In addition, the assumption that secular trends will continue may have influenced results, Ward and colleagues noted.