News reports from the past few years stating that the United States had “turned a corner” on childhood obesity may have been a bit too jubilant, suggests a new study.

An analysis of long-term trends for 2- to 19-year-olds shows that obesity has not decreased for any age group. In fact, many subgroups saw a rise in obesity.

Duke University researchers examined changes in body weight status from 1999 to 2016 for children ages 2 to 19 years using data from the National Health and Nutrition Examination Survey (NHANES).

They found that childhood obesity has increased since 1999, with recent spikes in class 1 obesity among children ages 2 to 5, and in the overweight category among females ages 16 to 19.

In the latest data for 2015–2016, obesity also increased with age, rising from 26 percent among 2- to 5-year-olds, to 41 percent for 16- to 19-year-olds.

The study was published today in Pediatrics.

The Centers for Disease Control and Prevention (CDC) now recommends dividing obesity into three classes based on body-mass index (BMI). The highest category, class 3, is sometimes called “extreme” or “severe” obesity.

Obesity increases the risk of diabetes, heart disease, stroke, arthritis, and even some cancers. Children who have obesity are at higher risk of having obesity as adults.

Researchers also found significant health disparities among certain racial and ethnic groups.

Hispanic females saw the most striking increase in obesity between 1999 and 2016. Hispanic males also had large increases in overweight and class 2 obesity during that time.

Hispanic and African American children had the highest rates of obesity for any racial or ethnic group in 2015–2016. This divide was worse for class 3 obesity — Hispanic and African American children had rates three to four times higher than white children.

Asian American children had the lowest rates of obesity during the most recent period.

One strength of the data is that NHANES uses actual height and weight measurements to calculate BMI.

But the survey doesn’t follow the same students over time, so researchers can’t say that specific children are developing obesity. Still, they believe that the data is representative of childhood obesity across the country.

The researchers and other researchers also caution against looking at only the most recent changes because it can take several years for a trend to be clearly visible.

“Maybe we should wait a little bit longer before making a strong conclusion,” said Xiaozhong Wen, PhD, an assistant professor of biological sciences in the Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo, who was not involved in the study.

Wen pointed out that obesity rates for both boys and girls move up and down between some data cycles. But the overall trend from 1999 to 2016 was toward higher rates of obesity.

Targeting childhood obesity earlier

Obesity is a complex disease with many factors driving it, including poor diet, lack of physical activity, sleep deprivation, and environmental factors during pregnancy and childhood.

Some programs have focused on reducing obesity among school-age children, such as by promoting greater physical activity during and after school, restricting sugar-sweetened beverages in schools, and redesigning school menus.

More research, though, shows that what happens early in a child’s life can affect their risk of having obesity later on. This opens the way for earlier interventions.

In one study, Wen and his colleagues found that infants whose mothers smoked cigarettes while pregnant are at risk of greater weight gain during the first two years of life.

“Right now, I am trying to use smoking cessation during pregnancy as one strategy to reduce rapid infant weight gain and later childhood obesity,” said Wen.

That study was published last year in the Journal of Pediatric Psychology.

Even the foods children eat as infants may affect their eating habits later on — and their risk of obesity.

Wen said that a child’s first year is critical for the development of taste preferences and the establishment of eating habits.

Exposing infants to vegetables more often may help them like these foods when they are older. This can make later health programs more successful.

“You can change the school menu, but a lot of kids don’t like vegetables because they have already developed their taste preferences,” said Wen. “It’s harder to alter them when the kids are older. So adding vegetables to the menu will just make them unhappy.”

Wen thinks that more attention also needs to be paid to choosing the right programs for widespread adoption.

“Some good research studies cannot be put into the real world. But some interventions that exist in policies may not be evidence-based,” said Wen. “We need to mesh these two things — policy should be based on good research evidence.”

In spite of the challenges, he thinks we have the tools we need to reverse the obesity trend among children.

“It’s not an easy job,” said Wen. “I think if we work together, we should be able to find a solution — soon, I hope.”