Young Shuar differ from most Western children in so many ways, though, including their genetics, that interpreting that study’s findings was challenging, Dr. Urlacher knew. But he also was aware of a more-comparable group of children only a longish canoe ride away, among Shuar families that had moved to a nearby market town. Their children regularly attended school and ate purchased foods but remained Shuar.
So, for the newest study, which was published in January in The Journal of Nutrition, 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.
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.
What differed most were their diets. The children in the market town ate far more meat and dairy products than the rural children, along with new starches, like white rice, and highly processed foods, like candy. In general, they ate more and in a more-modern way than the rural children, and it was this diet, Dr. Urlacher and his colleagues conclude, that contributed most to their higher weight.
These findings should not romanticize the forager or hunter-gatherer lifestyle, Dr. Urlacher cautions. Rural, traditional Shuar children face frequent parasitic and other infections, as well as stunted growth, in large part because their bodies seem to shunt available calories to other vital functions and away from growing, Dr. Urlacher believes.
But the results do indicate that how much children eat influences their body weight more than how much they move, he says, an insight that should start to guide any efforts to confront childhood obesity.
“Exercise is still very important for children, for all sorts of reasons,” Dr. Urlacher says. “But keeping physical activity up may not be enough to deal with childhood obesity.”