Does an infant’s body fat relate to cognitive and motor development?
Northeastern researchers are looking beyond weight and length to inform an infant’s neurological development.
As every parent knows, an infant’s early life is a series of milestones. From logging every development to regular checkups with the pediatrician to monitor body length, head circumference and weight.
Growth charts and other standard measures for infants of the same age are set by the World Health Organization (WHO) and are meant to track progress and offer guidance when intervention might be needed.
An infant who measures “larger, longer and bigger” on the WHO’s growth chart typically also tends to test high in cognition and motor function, said Lauren Raine, assistant professor and principal investigator of the Interdisciplinary Health, Body Composition and Neuroscience Lab at Northeastern University.
But what if the makeup of an infant’s weight — or the share of the type of tissues that comprise the weight — gives us better clues to how well they will perform in these tests, which could have lifelong implications? Northeastern researchers are studying the correlation. Currently in the data-collection phase, the research aims to understand how an infant’s makeup of fat mass and fat-free, or lean, mass play a role in cognition and motor development.
“Looking at weight and not body composition doesn’t tell us the entire story,” Raine said.
Body composition, explained Raine, includes various components in the body, including the percentage of body fat, as well as fat mass, lean body mass, muscle, bone and body water within the body, according to the National Institutes of Health.
Researchers and physicians use body mass index, or BMI, to estimate body composition based on weight and height, but that measure, along with weight, ”don’t actually tell us what type of tissue is driving this relationship,” Raine said. A greater percentage of a certain type of tissue in an infant could point to either better or worse cognition and motor development scores, she noted.
There are two main types of tissue that researchers like Raine pay attention to: Fat mass, or adipose tissue, and lean tissue such as bones, muscle and organs. An average healthy adult is made up of about 21% fat mass and 79% lean mass, she added. But infants go through a large swing in their body composition early in life, with about 10% fat mass at two weeks old up to 30% at six months old, before tapering off as they age, Raine said.
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Fat tissue is necessary for many things, including storing energy and providing insulation and organ protection. Too much of this type of tissue, in addition to being a risk factor for several health issues, has been connected to poor cognition in adults, said Charles Hillman, director of the Institute for Cognitive and Brain Health. Raine’s own research in children between the ages of 8 and 11 found that those with lower body fat and greater aerobic fitness have decreased symptoms of anxiety and depression.
To understand how body composition could affect infants’ cognition, Raine turned to a group of 40 healthy infants who were older than 32 weeks. Each infant in the study was tested using the Bayley Scales of Infant and Toddler Development, a widely-used tool to measure cognition — including memory, processing, executive function and attention — and motor skills, including rolling over, walking, dexterity and hand-eye coordination.
The infants’ performance on the Bayley Scales was compared to their body composition, which were measured using two types of standard, non-invasive machines that calculate body fat percentage, fat mass, and lean mass in minutes. One machine is meant for infants weighing under 8kg while the other is meant for anyone weighing more than that.
Raine presented her preliminary findings to a crowd of more than 150 people at the Institute for Cognitive and Brain Health’s Institute Day on Tuesday.
Raine is also working with Laurel Gabard-Durnam, developmental cognitive neuroscientist and director of the PINE Lab – which stands for Plasticity in Neurodevelopment and focuses on how experiences influences thoughts and behaviors in infants and adolescents – as well as with Emily Zimmerman, chair of Northeastern’s Department of Communication Sciences and Disorders. Their work is being supported by a Northeastern TIER grant, which offers funding for interdisciplinary research and faculty collaboration.
Raine’s initial findings suggest that an infant with more fat mass had worse cognitive and fine motor scores, and an infant with more fat-free mass had better performance in these two tests.
“This tells a very different story than the BMI. In fact, it kind of contradicts the BMI story, in that it’s not just, a larger baby does better on these tests. It’s a baby with more fat-free mass (that) does better on these tests,” she said.
Further, experts have begun to move away from placing a high emphasis on solely BMI for diagnosing obesity, pointing to its unreliability in measuring excess fat tissue.
More research needs to be done with a larger sample size to show significant trends related to gross motor skills, Raine said.
These findings could offer opportunities for early intervention, Hillman said. “It could eventually inform physicians who treat children with excess [fat tissue] and get them on the right track,” Hillman said, adding there are implications “for brain health, cognitive health and mental health across the lifespan.”
Raine said that the preliminary findings “make me pause to rethink how we monitor infant growth, that maybe the WHO curves are … not as informative as other metrics.”
