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A new study showed how even extremely active children don’t burn many more calories than sedentary counterparts. Getty Images
  • A new study looking at children in the Amazon found that diet, not a lack of physical activity, may be behind childhood obesity increase.
  • The study found that children in the Amazon did not burn substantially more calories than their counterparts in developed urban countries.
  • Experts say parents can encourage children to eat a healthy varied diet and stay active.

The childhood obesity epidemic is often blamed on children being far less active than previous generations. But what if the problem is far more simple than that?

Researchers studied children in the U.S. and U.K., and compared them with the children of a hunter-gatherer tribe in the Amazon to discover differences in physical activity and the amount of calories they burned.

What they found was incredibly surprising.

Hunter-gatherer children don’t spend more calories in their everyday lives than children in the U.S., but they do spend calories differently.

Conventional wisdom says if we exercise more, we spend more total calories.

However, recent studies suggest that total daily energy expenditure is actually limited within a narrow range. The more you consistently exercise, the fewer calories are spent on other metabolic tasks. No extra calories will be burned past a certain point.

There had been no research done that directly tests this theory of energy use among children living in challenging environments — until now.

According to Samuel Urlacher, PhD, assistant professor of anthropology at Baylor University, the findings demonstrate that Amazonian children with physically active lifestyles and chronic immune challenges (like parasites) don’t actually burn more calories than sedentary children living in the U.S.

For the hunter-gather children, there may be other factors, such as infection rates, that contribute to their ability to gain weight. However, because obesity isn’t a health issue for this population, this new research raises the possibility that obesity in children may be more about what they’re eating than how much exercise they’re getting.

“You can’t just spend unlimited calories on growth, physical activity, and immune activity,” Dr. Urlacher told Healthline. “This is really what we set out to test for the first time with kids. We were actually able to measure, instead of just estimate, energy expenditure in populations that have to deal with chronic immunological challenges and high level physical activity.”

The study was published December 18 in Science Advances.

To investigate how children spend calories, Urlacher and team collected data from 44 children of an Amazonian people called the Shuar that were between the ages of 5 and 12. They compared that data to those of comparable children in the U.S. and the U.K.

To measure the children’s calorie use, researchers used gold-standard isotope-tracking and respirometry methods, the first time that either state-of-the-art approach has been used among children in a preagricultural population, according to the study authors.

This information was combined with data about physical activity, immune activity, nutritional status, and growth.

“We were interested in working with kids because a lot of the metabolic disease trajectories are set early in life during these plastic periods when metabolism is responding to the environment,” said Dr. Urlacher. “So we thought by investigating the energy regulation early in life, that will say something about growth and about the propensity for things like obesity and metabolic disease.”

The study found that Shuar children are about 25 percent more physically active than industrialized children. Researchers also found an approximately 20 percent higher resting metabolic rate than American or British children (mostly because they also have elevated immune system activity).

Yet, despite the differences in environment and lifestyle, the total number of calories that Shuar children burn every day isn’t very different from that of children in industrialized countries.

“The really surprising part for us was how robust the findings are. I think we set out expecting that maybe the Shuar aren’t expending as many calories as you’d expect, but maybe they’re still a little bit higher, and that’s not the case at all,” said Dr. Urlacher.

The researchers theorize that there are tradeoffs because of this limit to energy use that may often limit physical growth. This could help us better understand poor childhood growth and the associated increased risk for adult obesity and diseases like type 2 diabetes. A high degree of physical and immune activity may reduce energy available for growth, even when there’s more than enough food.

Obesity affects a significant number of children in the U.S.

According to the Centers for Disease Control and Prevention (CDC), almost 14 percent of children 2 to 5 years old, 18 percent of children 6 to 11, and 21 percent of children 12 to 19 have obesity. But this is just one study and it doesn’t mean that parents should give up on having kids be active in favor of a strict diet.

Lucie Silver, pediatric exercise physiologist in the Healthy Weight Center at Helen DeVos Children’s Hospital explained that kids should not be put on a strict low calorie diet the way adults may take on in order to lose weight.

“Well, kids’ bodies are a little bit different because they’re still growing, their metabolism and everything works differently than an adult who’s calorie restricting or counting,” said Silver. “It’s more important to focus on what is going into the body. Are the things they’re eating comprised of healthy foods that will help them grow?”

Silver pointed out that it is difficult to workout long enough and hard enough to counteract a diet high in fat and calories.

“It’s really hard to out-exercise a poor diet. We do need to be conscious of what kids are eating, because there’s a lot more that goes into that than just feeding them healthy,” Silver said.

Sandra Elizabeth Ford, MD, FAAP, and director of the DeKalb County Board of Health in Georgia, said as a pediatrician she understands the challenges of monitoring children’s diet.

“Particularly with adolescents, any attempt to even comment on either choice or quantity of food can be considered bullying or fat shaming,” said Ford. “What should be a simple discussion can escalate into a battle of wills, where your child will overeat or eat poorly simply out of spite.”

Dr. Ford emphasized that exercise still plays an important role in maintaining optimal health. “I always recommend parents increase physical activity rather than restrict food when there are concerns about a child’s weight.”

She explained that even a daily walk after dinner is more likely to achieve results than policing every bite of food on your child’s plate. Dr. Ford explained that obesity tends to be familial, so involving the entire family can ensure that physical activity becomes a lifestyle change rather than something that has to be endured.

“Even if weight is not a family-wide issue, physical activity has also been shown to reduce stress and contribute to overall well-being, so it’s a win for everyone!”

Exciting new research suggests there are limits to how many calories can be burned exercising.

According to researchers, there are limits to how many calories we can burn daily. Past that point, we take energy away from other bodily processes but don’t use up any extra.

Experts emphasize that physical activity is still an important part of a healthy lifestyle and should be combined with healthy food choices to optimize health.