Mouse Neurons

Relating Obesity to Brain Health

Is obesity a neurologic or a metabolic disease? Truthfully it’s a condition that defies tidy definitions, perhaps because it comes in many different forms. But in the past few weeks, we’ve been treated to a stream of new studies that relate obesity to brain health.

A new study in Molecular Psychiatry found a significant risk for earlier onset of Alzheimer’s disease in people with obesity at midlife. They also found risk for a greater burden from Alzheimer’s. It goes without saying that an increased risk is a clue for further research, not proof of cause and effect. But this research, along with prior observations that midlife obesity is a risk factor for Alzheimer’s, suggests that it’s worth investigating whether a healthy BMI can delay the onset of the dementia.

In another new study this week, investigators led by Tobias Niedermaier found a 50% increase in the risk of a common brain tumor (meningioma) for people with obesity. In the same study, they found an association between physical activity and a reduced risk for that same kind of brain tumor, though the evidence for this relationship was more limited.

Finally, new animal research from Vanderbilt University this week provides deeper insight into the mechanism by which a high fat diet can disrupt brain signals that normally regulate appetite. They found a group of proteins that help determine how rewarding high fat foods are. Study author Aurelio Galli explained:

Our findings reveal a system that is designed to control eating of rewarding foods that are high in fat and possibly sugar. This system can be hijacked by the very foods that it is designed to control. Eating a high-fat or high-carbohydrate diet feels rewarding, but also appears to cause changes in the brain areas that are involved in controlling eating, by causing for example insulin resistance. Our study shows that when specific signaling in these areas of the brain is disrupted, it leads to a vicious cycle of increasing, escalating high-fat diet intake that likely further cements changes in these brain areas.

These new findings are but a small sampling of an ongoing flood of information that is building the evidence base for the effects of obesity on brain health. Considering this evidence makes the archaic view of obesity as a purely behavioral problem virtually impossible to defend.

But the real value is the clues that are accumulating for research into more effective treatment strategies.

Click here and here for more on the link between midlife obesity and Alzheimer’s. Click here and here for more on the link between brain tumors and obesity. Click here and here for more on the effect of high fat diets on brain signaling.

Mouse Neurons, photograph by S. Jeong, NICHD NIH / flickr

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September 24, 2015