We all know the simple fact that weight gain occurs when an individual’s energy intake exceeds his energy expenditure – that is, when more calories come in than go out. But what many don’t know is that during early childhood, almost half of our bodies’ energy is used by the brain.
Co-authors Christopher Kuzawa of Northwestern University and Clancy Blair of New York University School of Medicine published a paper in the journal Proceedings of the National Academy of Sciences (PNAS) titled:
“A hypothesis linking the energy demand of the brain to obesity risk,” that proposed that different energy needs for brain development among children could have an impact on the energy expenditure and weight gain patterns.
“We all know that how much energy our bodies burn is an important influence on weight gain,” said Kuzawa, professor of anthropology in the Weinberg College of Arts and Sciences and a faculty fellow with the Institute for Policy Research at Northwestern.
“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.”
Could school programs help?
The authors say that programs meant to stimulate brain development – like the preschool program Head Start – could possibly influence the brain’s pattern of energy use, but this is still not completely known.
“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.”
All of this began in 2014 when Kuzawa and his colleagues found in a study that five-year-olds’ brains consume a lifetime peak of two-thirds of the body’s resting energy expenditure – almost half of the total expenditure. They found that the times during early childhood that showed weight loss were also times of increased brain energy expenditure. The less energy is needed for brain development as children grow and become adolescents, the easier it is for them to gain weight.
“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.