National Post: Does fat affect your brain? Study finds obese have less grey and white matter in key areas

As Sharon Kirkey at The National Post writes:

A tiny but provocative Canadian-led study suggests overweight and obese people have significantly less grey and white matter in key brain regions, offering what the researchers believe is a “biologically plausible explanation” for why heavier people tend to have reduced cognitive functioning, greater impulsivity and “altered reward processing.”

The study is based on sophisticated brain images of 32 otherwise healthy adult volunteers recruited from two Baltimore neighbourhoods, and the researchers did not test their subjects’ mental acuity or performance.

However, the findings appear to fit with mounting evidence linking higher body mass with poorer impulse control and other “cognitive deficits” that may undercut a person’s efforts to lose weight.

“It has been suggested that body composition itself might somehow affect the neural systems that underlie cognition, motivation, self-control and salience processing, which would in turn affect one’s ability to make better lifestyle choices,” the researchers write, for example, “forgoing immediate and/or highly salient rewards for the sake of longer-term health and wellness goals.”

Other researchers have linked obesity to accelerated, age-related brain shrinkage and early-onset dementia.

Worldwide, an estimated 2.1 billion people are overweight or obese. In 2014, 20 per cent of Canadian adults — roughly 5.3 million people — reported height and weight that classified them as obese.

For the new study, published in the latest issue of the journal Frontiers in Neuroscience, researchers from Canada and the U.S. imaged the brains of 16 men and 16 women. They excluded anyone with a history of brain injury or disease, mental illness, substance abuse or other disorders.

They measured BMI and body fat percentages, and then looked at how individual differences in body composition were related to differences in brain structure and function.

“We looked for changes across the whole brain, but we also looked at specific networks,” said co-author Chase Figley, an assistant professor in the department of radiology at the University of Manitoba and Winnipeg Health Sciences Centre.

When they examined the brain as a whole, people with a higher BMI or body fat counts had, in fact, slightly more grey matter, on average. “And there was no significant difference in terms of white matter volume, globally speaking,” said Figley.

But there were associations when they looked at different specific networks.

In particular, heavier and fatter people had less grey and white matter in the “salience network,” what Figley describes as the “seat of motivation, willpower, and the ability to persevere through physical and emotional challenges.”