When a person’s food intake exceeds their energy expenditure, they gain weight. To put it simply, weight gain occurs when calories taken in exceed the amount of calories taken out. But we all sort of knew that already, didn’t we? Well here is another fact: nearly half of the body’s energy is used by the brain during early childhood. And that’s where the children’s weight gain phenomenon lies.
A recent research, published in the journal Proceedings of the National Academy of Sciences (PNAS), states a hypothesis “linking the energy demand of the brain to obesity risk.” Co-authors Christopher Kuzawa of Northwestern University and Clancy Blair of New York University School of Medicine suggest that variation in the energy needs of brain development across kids - in terms of the timing, intensity and duration of energy use - could influence patterns of energy expenditure and weight gain.
"We all know that how much energy our bodies burn is an important influence on weight gain," said Kuzawa. "When kids are 5, their brains use almost half of their bodies' energy. And yet, we have no idea how much the brain's energy expenditure varies between kids. This is a huge hole in our understanding of energy expenditure."
"A major aim of our paper is to bring attention to this gap in understanding and to encourage researchers to measure the brain's energy use in future studies of child development, especially those focused on understanding weight gain and obesity risk,” added the professor of anthropology in the Weinberg College of Arts and Sciences and a faculty fellow with the Institute for Policy Research at Northwestern.
The study found that preschool programmes designed to stimulate brain development through enrichment, may also influence the brain's pattern of energy use. "We believe it plausible that increased energy expenditure by the brain could be an unanticipated benefit to early child development programs, which, of course, have many other demonstrated benefits," Kuzawa said. "That would be a great win-win."
The hypothesis was inspired by a 2014 study conducted by Kuzawa and his colleagues. The research showed that the brain consumes a lifetime peak of two-thirds of the body's resting energy expenditure, and almost half of total expenditure, when kids are five years old. That study also revealed that ages when the brain's energy needs increase during early childhood are also ages of declining weight gain.
"This finding helped confirm a long-standing hypothesis in anthropology that human children evolved a much slower rate of childhood growth compared to other mammals and primates in part because their brains required more energy to develop," Kuzawa said.