National childhood obesity rates rose from the 1970s into the early 2000s and have grown much more slowly since then. We recently spoke with Diane Schazenbach, director of the Institute for Policy Research at Northwestern University, about new research she and colleagues published using various federal data sets to examine some of the long-term trends in obesity rates. Below is a brief interview about the research.
How Childhood Obesity Rates Have Changed Over Time
In the big picture, what does your research show about how obesity rates have changed over the last few decades?
Overall, the rate of childhood obesity has more than tripled over the last four decades—rising from 5 percent in 1978 to 18.5 percent in 2016. Of course, that is an alarming trend! In response, resources have poured into addressing childhood obesity, through public health efforts, reforms to school policies and nutrition assistance programs, and more. What we find is that there is a sharp break in trend—a leveling off—starting in 2003. These days, the prevalence of childhood obesity is still rising, but at a much slower rate than it used to.
To put this in concrete terms, from 1978 to 2003, the childhood obesity rate grew by about 1 percentage point every 2 and a half years. Since 2003, it’s closer to 1 percentage point per decade. More work to bring down childhood obesity rates is needed, for sure, but there is some good news here!
From 1978 to 2003, the childhood obesity rate grew by about 1 percentage point every 2 and a half years. Since 2003, it’s closer to 1 percentage point per decade.
For many years, Black and Hispanic youth have had higher obesity rates than White or Asian youth. How have those differences been changing over time?
That’s right. In 2016, 26 percent of Hispanic children had obesity, compared to 22 percent of Black children and 14 percent of White children. We find that obesity rates among white children have remained steady since 2002 and are no longer increasing. Black and Hispanic children, on the other hand, have not seen the same progress and their obesity rates are continuing to increase. As a result, the gaps in obesity rates have been increasing between groups. For what it’s worth, unfortunately our national data, the National Health and Nutrition Examination Survey, do not include a large enough sample for us to reliably analyze obesity among Asian children.
One pattern we noticed that was surprising was that a lot of this increasing gap between Black and Hispanic children on the one hand and White children on the other hand happens by the time children are age 5. After that point, all groups experience increases in obesity at about the same rate. This suggests that we need to be aiming more of our efforts to address obesity at younger children, and think about the food and activity environments they face in preschools, child care, and in their homes.
You also examined how rates differ between males and females. What did you see there?
The overall trends show that boys and girls have similar rates of obesity, and have experienced the same patterns of gains over time. In fact, we had to argue to keep the results by gender in the research, because reviewers did not think the results were interesting! We pushed back, saying that the lack of difference is itself an interesting finding!
How about how obesity rates change as children get older?
We found some pretty striking patterns as children get older. In particular, we find that a birth cohort’s obesity rate increases steadily from age 2 through about age 10, but that it levels out after that, so that obesity rates stay steady from ages 10 through 18. Of course, this pattern may differ for individual children—that is, in their teenage years some kids hit a growth spurt and see their BMI fall while others see theirs increase. But overall, as a group, we find that kids who were born in a certain year have about the same obesity rates at ages 11, 14 and 17.
There are many people and organizations – nonprofits, foundations, policymakers, businesses, schools, and others – working to help children grow up at a healthy weight. How should they use your new research to inform their strategies?
First, I’d want to point out that the slowing down of the rate of increase in obesity that started around 2003 is real progress, and is likely due to the efforts that these groups have put into helping children grow up at a healthy weight. It’s always difficult to prove this statistically beyond a doubt, but I’d say it is more likely than not that these efforts helped out. If the upward trend in obesity had not been slowed, today childhood obesity rates would be 10 percentage points higher than they actually are.
We probably want to direct additional resources at promoting healthy weights in younger children, especially in preschool years and extending through elementary school years.
But there is more work to be done, and I think we uncover a few important facts that should help inform this work going forward. We probably want to direct additional resources at promoting healthy weights in younger children, especially in preschool years and extending through elementary school years. I’d be quick to caution that we should not slow down our efforts at other ages, but instead we should think about new investments in younger children. Second, we need to keep working at finding successful strategies especially for Black and Hispanic children, where we have seen less progress.