Does Eating Fat Impair Your Thinking?

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Eating a high-fat, high-sugar diet may have a negative effect on more than just your physical health — it can also be harmful to your mental health. A study published last year in the journal Biological Psychiatry examined how sugar and fat affect the normal bacteria in the intestine and the impact that has on the brain’s functioning.

Prior research already determined that being overweight dramatically increases mental illnesses — particularly depression, dementia and stroke. “[Obesity] is associated with increased brain pathology and decreased brain function,” the article states. But this prior research did not get to the source of the problem, so the researchers dug deep — into the gut.

A team of researchers from Louisiana State University examined the gut microbiome, the microorganisms that everyone carries around in their intestines, to test their hypothesis. As diets high in sugar and fat have a profound effect in the gut microbiome’s core, they set out to see how bacterial changes in the intestinal tract impaired neurocognitive behavior. To do that, the researchers fed mice a normal diet, but some of the mice received a transplant of gut microbiota from mice that had been fed a high-fat diet. The result? Researchers found that mice that received the microbiota diet exhibited anxiety, repetitive behavior and impaired memory. One way that was exhibited is something called “marble burying,” which measures compulsive, anxiety-like behavior in mice.

“This study is preliminary,” New York University Clinical Associate Professor Lisa Sasson warns. “However, what we know from long-term studies is fat is a very important nutrient. The source of fat we consume is important.” If you’re concerned about your fat intake, it’s time to do your own gut check. Are you eating good fats? Sasson says, “Most fats in our diet should come from plant food, such as nuts, seeds, olive oil, avocado, fish, et cetera.”

Don’t let this be a license to load up on even the good fats. “Excessive amount of fat, regardless of the food source can lead to extra weight gain and possibly, as this article suggests, affect the microbiome,” Sasson cautions. So what’s your best bet on the fat front? “The best choice,” she says, “is to have meals that are a balance of foods from the different food groups: fruits, vegetables, whole grains, lean animal or [other] protein sources and healthy fats.”

This summer, take advantage of good fats by adding avocado to salads, nuts and seeds. Try Crab and Avocado for an outdoor lunch. Hold the mayo in that potato salad, and get some oily fish in your diet at your cookout with this easy cedar-plank salmon.

Kiri Tannenbaum is a graduate of Le Cordon Bleu Paris and holds an M.A. in food studies from New York University where she is currently an adjunct professor. When her schedule allows, she leads culinary walking tours in New York City and is currently at work on her first book.