Without some serious changes, the majority of U.S. children may be obese by the time they reach age 35, according to a new study.

Researchers from the Harvard T.H. Chan School of Public Health used data from the CDC and five longitudinal studies, accounting for 41,567 children and adults in all, to map out height and weight trajectories for a population of 1 million aging kids. They ran 1,000 different simulations to reach a prediction.

Based on those projections, which were published Wednesday in the New England Journal of Medicine, the researchers estimate that 57% of children who are currently between ages 2 and 19 will be obese by the age of 35, if current trends continue. Today, about 38% of American adults age 20 and older have obesity.

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“On current trends, obesity is going to be a problem for most kids as they grow older,” says Zach Ward, the study’s lead author and a PhD candidate in health policy at the Harvard T.H. Chan School of Public Health. “We really need to start thinking about really scaling up prevention efforts.”

The researchers also found that while childhood obesity is a risk factor for adult obesity, plenty of normal-weight children are still at risk of developing obesity later on. In fact, the team found that the majority of obese 35-year-olds were not obese as children.

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The study suggests that curtailing childhood obesity could have a large impact on public health, particularly given the evidence that weight issues during adolescence tend to stick around into adulthood.

“Just because a child is at a healthy weight, that’s certainly a good thing, but we need to ensure that they maintain a healthy weight as they grow older,” Ward says. “It also points to the importance of early interventions”—such as school nutrition programs, reducing the consumption of sugar-sweetened beverages and limiting screen time—”for children who already have obesity.”

Write to Jamie Ducharme at jamie.ducharme@time.com.