Kids With Obesity More Likely To Have Cognitive Issues As Adults, 30-Year Study Finds

Obesity in children has been linked to a number of issues later in late life, such as diabetes, coronary artery disease, and fatty liver disease. But obesity in childhood doesn’t just affect physical health. A new study finds that both a child’s hip-waist ratio and physical fitness is linked to their cognitive abilities later in adult life.

“The really big takeaway message is how important it is to be physically active when people are young, in childhood,” says study author Michele Callisaya, Ph.D. from the National Centre for Healthy Ageing at Monash University in Melbourne. “And that's important, we now know from this study, for midlife brain health.” The findings suggest that schools and parents should promote physical activity as much as possible, she says.

Callisaya’s team started their research with 1,244 children in Australia in 1985, all of whom were between the ages of 7 and 15. They tested the participants on fitness parameters such as muscular endurance, power, and heart and lung performance — via a 1.6 kilometer run, pushups in 30 seconds, long jump, and a 50 meter sprint — as well as their waist sizes. Then, between 2017 and 2019, when most participants were between the ages of 39 and 50, they were tested online to assess their cognitive function, such as processing speed, attention, and memory.

In a study published in the Journal of Science and Medicine in Sport, the results show that there’s a link between childhood fitness and middle age cognitive ability. The kids who scored highest in the fitness test and who had the lowest waist-to-hip ratio in their youth performed better on the computer cognition tests later in life. The correlation remains strong even when factoring out many other factors of the participants’ life, such as their socioeconomic background, how well they performed in school, and habits such as smoking or drinking alcohol.

There could be two reasons for this association, Callisaya says. First, physical activity could have a direct effect on the brain, increasing blood flow. Physical activity could form new neurons, new connections, and new blood vessels, she says. Second, if children don’t exercise and have obesity, they're more likely to have high blood pressure, diabetes, and other health conditions that are known risk factors for dementia and poor brain health later on.

Although the new study shows a link between obesity in childhood and cognition as an adult, “it does not prove one causes the other, nor helps us understand the how,” says Florencia Halperin, M.D., an obesity researcher and the medical chief officer at Form Health, who was not involved in this research.

“Fitness, BMI, cognition…these are all multi-factorial aspects of health,” Halperin says. “They are determined by a very complex interaction between genetics, biology, environment, and many more factors.” Obesity could conceivably lead to declined cognition, she says. Or it could be that another underlying element tracks with both things — theoretically there could be a genetic pattern that affects both your cognition and your BMI.

The researchers did not assess cognitive levels in childhood though, so it’s also possible that people with lower adult cognition also had lower cognition levels as children.

The correlation the study found also isn’t as strong as it could be, says Krista Casazza, Ph.D., a nutrition scientist and the director of research at Florida Gulf Coast University, who was not involved in the study. The data from the research shows that the more fit you are as a child, the better your cognition as an adult. But it doesn’t as strongly support that the less fit you are, the less good your cognition is, Casazza notes.

“There's clearly a link between obesity, glucose control, obviously waist-hip ratio, the whole metabolic syndrome, and impaired cognition. It's likely a multitude of things,” Casazza says. A child who was overweight probably got bullied at school, especially in the ‘80s, she says, and that could have impacted their growth and development. And many lifestyle conditions were completely different 30 years ago; it’s not like comparing a child from today and how they’ll be in 2050.

“There's lots of tricky things that we can't measure,” Callisaya says. “But I think childhood fitness is still a good marker of someone's brain health later on. We can't say it's causal. But if it is a marker, then there needs to be a really complex look at why, and what we can do to help those kids become healthier.”