Young Shuar is different from most Western children in many ways, although interpreting the results of this study, including their genetics, was challenging, Dr. Urlacher. But he was also aware of a comparable group of children only a long canoe ride away, among Shuar families who had moved to a nearby market town. Her children attended school regularly and ate groceries they bought, but remained Shuar.
For the latest study, published in the Journal of Nutrition in January, he and his colleagues received permission from rural and relatively urban Shuar families to assess the body composition and energy expenditure of 77 of their children between the ages of 4 and 12, while at the same time tracking their activities with accelerometers and collecting data on what they ate.
The urban Shuar children were found to be considerably heavier than their rural counterparts. About a third was overweight according to World Health Organization criteria. None of the rural children was. The urban children were also generally more sedentary. But all children, whether rural or urban, active or not, burned roughly the same number of calories every day.
What differed most was their diet. 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 more modernly than the rural children, and that diet, Dr. Urlacher and his colleagues contributed most to their higher weight.
These findings shouldn’t romanticize the lifestyle of choppers or hunters and gatherers, warns Dr. Urlacher. Rural, traditional Shuar children are exposed to frequent parasitic and other infections, as well as stunted growth, in large part because their bodies seem to keep the calories available for other vital functions and growth, believes Dr. Urlacher.
However, the results suggest that the way children eat affects their body weight more than how much they move.
“Exercise is still very important to children for all sorts of reasons,” says Dr. Urlacher. “But maintaining physical activity may not be enough to cope with childhood obesity.”