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Less Physical Activity in Children Adds Pounds and Inches

A new study found that children who participated in less physical activity were heavier and taller than their more active peers. The study was conducted by Hunter College post-doctoral research fellow Samuel Urlacher and Karen Kramer of the University of Utah.

Humans spend energy on a number of critical life tasks, including physical activity and growth. When caloric intake is limited, metabolic competition for calories can lead to tradeoffs between growth and physical activity. But when children cut back on physical activity, the competition is less, leaving their bodies free to grow more. At least that is the theory.

The new study, published in Scientific Reports, was the first of its kind to prove the theory in humans.

The researchers used a rare set of data of a Mayan farming community in Mexico. The data spanned 20 years, during which the community experienced early economic development, which led to more time in school for children, less physical labor, and less time in physical play. When the study began, the community had no electricity, running water, mechanized farming, or permanent school.

“We recently recognized that the kids are much larger now than before, so we began to wonder if energy savings from reduced physical activity was being redirected to promote greater growth,” says Urlacher.

When they compared Mayan children in 1992 to children in the same community in 2012, they found the children were far less active in the 2012 cohort. This reduction resulted in less energy expenditure — an average of 402 and 238 calories (kcal) a day less for males and females, respectively.

As a result, the children in 2012 were on average 2.9 inches (7 percent) taller, 6.6 pounds (17 percent) heavier, and had skinfold measures of subcutaneous body fat that were 19 percent greater than those of children in 1992. The differences could not be explained by diet as there was minimal dietary changes in the community.

“This finding has implications for understanding the factors causing the global rise in obesity,” says Urlacher. “More research is needed, but our results suggest that ongoing changes in early life physical activity, in addition to changes in diet, may play a critical role promoting poor metabolic health in the developing world.”

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Explore This Work
Evidence for energetic tradeoffs between physical activity and childhood growth across the nutritional transition
Scientific Reports, 2018

Work By
Samuel Urlacher (post-doctoral research fellow, anthropology) | Profile

Colleges and Schools
Hunter College

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