November 29, 2017
Over half of today's children in the United States will be obese at the age of 35 if existing trends continue, despite the fact that currently, less than 20% of them are obese, a new simulated growth trajectory model indicates.
"Right now, about 17% of children between the ages of 2 and 19 have obesity," lead author of the new research, Zachary Ward, MPH, Harvard TH Chan School of Public Health, Boston, Massachusetts, explained in an email to Medscape Medical News.
"But we project that the majority of them — 57% — will have obesity when they turn 35," he added.
In fact, only those children with a current healthy weight have less than a 50% chance of becoming obese by the age of 35 years, the researchers say in their paper, published in the November 30 issue of the New England Journal of Medicine.
And perhaps not surprisingly, early development of obesity predicted obesity in adulthood, especially for children who were severely obese.
"Our findings highlight the importance of prevention efforts for all children as they grow up and of providing early interventions for children with obesity to minimize their risk of serious illness in the future," Dr Ward noted in a statement from his institution.
Obesity Is a Trajectory That Is Difficult to Change
In the United States, obesity has declined recently among children between the ages of 2 and 5 years and has stabilized among those between the ages of 6 and 11 years of age but continues to rise among adolescents and adults, say Dr Ward and colleagues.
And although the obesity epidemic has been well characterized at a population level, less is known about the individual-level risk of adult obesity for a given child on the basis of current weight and age, they explain.
For their estimates, the researchers pooled five nationally representative data sets involving 41,567 children and adults who had repeated measures of height and weight over time, and they developed a simulation model to predict individual growth trajectories. They then created 1000 virtual populations of 1 million children through the age of 19 years that were representative of the 2016 US population and projected their trajectories in height and weight up to the age of 35 years.
"Among obese children, we found that the probability that they will still be obese at the age of 35 years increased with age," they report — that risk being almost 75% at the age of 35 if children are obese at the age of 2 and over 88% if they are obese at the age of 19.
Excess weight gained during childhood can therefore put children on a trajectory that is difficult to change, the authors say.
And this is particularly true when it comes to those with severe obesity — a condition that currently affects 4.5 million children in the United States. This was defined as 120% or more of the 95th percentile in children or BMI 35 mg/kg² or greater in adults.
At age 2, these children have only a one in five chance of not having obesity at age 35; at age 5, that chance drops to just one in 10.
Maintaining Healthy Weight Throughout Childhood Cuts Risk of Adult Obesity
In contrast, children who are not obese at the age of 2 have a lower risk of becoming obese by the time they reach 35, provided they maintain a healthy weight through to the age of 19.
For example, if children are not obese at the age of 2, they have a 57.8% probability of being obese at the age of 35, but if they are still at a healthy weight at the age of 19, that risk drops down to 44.4%, the researchers point out.
But despite these figures, "we also found that the majority of obese 35-year-olds were not obese as children," the authors say.
In other words, approximately half of the prevalence of obesity seen in adulthood begins in childhood, while the remainder is explained by adult-onset obesity.
"It is critically important to implement policies and programs to prevent excess weight gain, starting at an early age," stressed senior author Steven Gortmaker, PhD, also of the Harvard TH Chan School of Public Health.
The research was supported in part by grants from the JPB Foundation, the Robert Wood Johnson Foundation, the Donald and Sue Pritzker Nutrition and Fitness Initiative, and the Centers for Disease Control and Prevention, including the Nutrition and Obesity Policy Research and Evaluation Network. The authors had no relevant financial relationships.
SOURCE: Medscape, November 29, 2017. N Engl J Med. 2017;377:2145-2153.