Inheriting Brains, Behaviors, and BMI

Obesity is a condition that we largely inherit. But that’s a tough concept for some folks to accept. Even the AHA misclassifies BMI as a “health behavior” – a mistake we keep hoping it will correct. Meanwhile, contrary evidence keeps coming. Brains, behaviors, and BMI are heritable and related.

Neurologic and Behavioral Dimensions of Obesity

For instance, a new paper in PNAS reminds us that both brain structure and behaviors are highly heritable. And they’re heritable in ways that predict a person’s risk for obesity. People with higher BMIs tend to have a thicker left prefrontal cortex. At the same time, the right side tended to be thinner. The left side of the amygdala tended to be larger in people with higher BMIs. And that region of the brain may play a role in responding to food cues.

The researchers found a pattern in a genetic basis for brain structure, behaviors, and BMI. Lead author Uku Vanik explains how this plays out:

We have this genetic urge to secure as much food as we can when food is available. Fast forward to now, we’re in this environment where food is always available.

People with higher obesity have slightly lower scores in cognitive flexibility or certain memory tests. Cognitive flexibility may allow you to see a nice burger, but then you will switch to a nice apple instead.

Neuroanatomy of Obesity

Complementing these findings is a new meta-analysis in the International Journal of Obesity. Isabel García-García and colleagues found robust evidence of a link between obesity and brain structure. Specifically, obesity and high BMI is more prevalent in people with less gray matter in areas of the brain responsible for executive control.

Clues, Not Answers

Taken together, these studies provide important clues. Not definitive answers for the biologic basis of obesity. These data represent findings of associations between genetic factors, brain structure, and obesity risk. Filling out the full picture requires more research.

But new research can apply these insights for interventions that work. And when it does, we can become ever more confident in our understanding of this disease. Just as we are now confident that obesity is not a behavior.

Click here for the study by Vanik et al and here for more from McGill University. For the study by García-García et al, click here.

Brain Maps of Associations Between BMI and Cortical Thickness. Figure from Vainik et al, PNAS, © 2018 National Academy of Sciences

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September 3, 2018