When children gain excess weight, the culprit is more likely to be eating too much than moving too little, according to a fascinating new study of children in Ecuador published in Oxford Journal of Nutrition. 

The in-depth study found that rural children, who run, play and forage for hours, are leaner and more active than their urban counterparts. But, they do not burn more calories day-to-day, a surprising finding.

The findings also raise questions about the interplay of physical activity and metabolism and might explain why exercise helps so little with weight loss, not only in children but for the rest of us, too.

The Oxford Journal of Nutrition

About the research

The study compared the lifestyles, diets and body compositions of Amazonian children who live in rural, foraging communities with those of other Indigenous children living in nearby towns, and the results shed light on possibly explaining the rising rates of obesity in both children and adults worldwide.

Inactivity vs overeating. Which is the main cause of obesity?

The issue of childhood obesity is of pressing global interest, since the numbers keeps rising, including in communities where it once was uncommon. Researchers point to a common theme – increasing childhood inactivity and junk food diets as drivers of youthful weight gain.

But which of these two might be contributing more to the weight gain – Inactivity or overeating ??

That question drew the interest of Sam Urlacher, an assistant professor of anthropology at Baylor University in Waco, Texas, who for some time has been working in and studying the Shuar people, an Indigenous population in Amazonian Ecuador.

The traditional Shuar live primarily by foraging, hunting, fishing and subsistence farming. Their days are hard and physically demanding, and their diets are heavy on bananas, plantains and similar natural starches. Their bodies are slight and the Shuar, especially the children are rarely overweight.

But are their wiry frames a result mostly of their active lives, Dr. Urlacher wondered?

Despite leading a very active lifestyle the hunter gatherers of Hadza tribe in Tanzania burned the same number of calories as more sedentary westerners – a prioneering study by Herman Pontzer

As a postgraduate student, Dr. Urlacher had worked with Herman Pontzer, an associate professor of evolutionary anthropology at Duke University, whose research focuses on how evolution may have shaped our metabolisms and vice versa.

In Dr. Pontzer’s pioneering research with the Hadza, a tribe of hunter-gatherers in Tanzania, he found that, although the tribespeople moved frequently during the day, hunting, digging, dragging, carrying and cooking, they burned about the same number of total calories daily as much-more-sedentary Westerners.

What does this mean?

Dr. Pontzer concluded that, during evolution, we humans must have developed an innate, unconscious ability to reallocate our body’s energy usage. If we burn lots of calories with physical activity for example, we burn fewer with some other biological system.

The result is that our average daily energy expenditure remains within a narrow band of total calories burnt which is helpful for avoiding starvation among active hunter-gatherers, but disheartening for those of us in the modern world who’s lifestyle is less active.

That’s why we find that more exercise does not equate to much of any weight loss, because the body is only willing to dispense of enough calories that it feels it needs to. (Dr. Pontzer’s published a new book on this topic titled, “Burn”).

Comparing the Shuar children in rural area vs children in urban areas

Dr. Urlacher used the research of Dr. Pontzer to compare two populations – the Shuar who lived a rural life vs those in urban areas in the Western countries such as United States and Britain.

In a 2019 study, he precisely measured energy expenditure in some of the young Shuar and compared the total number of calories they burned with data about the daily calories burned by sedentary and much heavier children in the United States and Britain.

And the totals matched. Although the young Shuar were far more active, they did not burn more calories over all.

Comparing rural Shuar to urban Shuar

Dr. Urlacher went even further for the newest study, which was published in The Journal of Nutrition. This time to make the data even more specific, in this study he and his colleagues gained permission from Shuar families, both rural and relatively urban, to precisely measure the body compositions and energy expenditure of 77 of their children between the ages of 4 and 12, while also tracking their activities with accelerometers and gathering data about what they ate.

Some Shuar families had moved to a nearby market town. Their children regularly attended school and ate purchased foods but remained Shuar.

The urban Shuar children proved to be considerably heavier than their rural counterparts. About a third were overweight by World Health Organization criteria. None of the rural children were. The urban kids also generally were more sedentary. But all of the children, rural or urban, active or not, burned about the same number of calories every day.

How is that possible? What differed most were their diets.

The children in the market town ate far more meat and dairy products along with new types of starches like white rice, and highly processed foods such as candy compared to the rural children.

In general, urban kids ate more food and in a more-modern way than the rural children, and it was this diet, Dr. Urlacher and his colleagues concluded that contributed most to their higher weight.

The results show that how much children eat and the types of foods they eat influences their body weight more than how much they move, Dr. Urlacher says. This is a different approach to how we look at curbing the obesity epidemic spreading all over the world today.

“Exercise is still very important for children, for all sorts of reasons, but diet is equally important to deal with childhood obesity.” ” Dr. Urlacher

What does all this mean?

As important as exercise is, eating natural foods heavy on vegetables, legumes, nuts, seeds and whole grains is what helps maintain a healthy weight.

We can exercise for hours to shed those pounds but the body will eventually only expend calories upto a certain point before saying “Nope, I need those calories for other functions.”

Think of it like a math formula. If we ate 2000 calories more than we need, expecting exercise to burn those calories off would require working out for hours and that too at a very high intensity, and eventually our bodies will resist the calorie burn at a certain point.

Want to lose those extra holiday pounds? Of course start exercising as muscle mass burns more calories, but to lose the excess weight we have to curb how much we eat.

Here’s the good news! If we eat vegetables, legumes, nuts and whole grains we can feel satiated and don’t have to go hungry to shed those extra pounds.

Source: The Journal of Nutrition Oxford Academia