Bad Eating Habits Can Hurt Brain, Not Just Waistline

A diet high in saturated fats and sugars can affect the parts of the brain that are important to memory.

Being overweight can raise blood pressure, cholesterol and risk for developing diabetes. It could be bad for your brain, too.

A diet high in saturated fats and sugars, the so-called western diet, actually affects the parts of the brain that are important to memory and make people more likely to crave the unhealthful food, says psychologist Terry Davidson, director of the Center for Behavioral Neuroscience at American University in Washington, npr.org reported.

“There’s a vicious cycle of bad diets and brain change,” he says. He points to a 2015 study in the Journal of Pediatrics that found obese children performed more poorly on memory tasks that test the hippocampus compared with kids who weren’t overweight.

He says if our brain system is impaired by that kind of diet, “that makes it more difficult for us to stop eating that diet. ... I think the evidence is fairly substantial that you have an effect of these diets and obesity on brain function and cognitive function.”

Research from the Cambridge Center for Ageing and Neuroscience published in July found that obese people have less white matter in their brains than their lean peers — as if their brains were 10 years older.

But if we understand how obesity affects the brain and memory, then maybe we could use that relationship to prevent people from becoming obese in the first place.

Lucy Cheke, a psychologist at the University of Cambridge, says her study in The Quarterly Journal of Experimental Psychology this November gives her some idea of how to do that.

  Memory Deficit

Her researchers asked obese and lean people to do a memory task that’s a virtual treasure hunt. The subjects had to hide something in a scene across various computer sessions, then they were asked what they hid, where they hid it and in which session.

The obese people were 15 to 20% worse than lean ones in all aspects of the experiment. The finding confirmed what other researchers had already seen in rodents. “This really picks apart spatial, item and temporal memory, as well as, crucially, the ability to integrate them,” which Cheke says is “one of the most fundamental aspects of memory.”

If you’re obese, she says, you might just be “10 to 15 to 20% more likely to not quite remember where you put your keys.”

However, even though we are beginning to understand that obesity affects the brain, we don’t exactly know how, says John Gunstad, professor and director of the Applied Psychology Center at Kent State University in Ohio.

He points out that obesity changes a lot about the body: blood sugar levels, the cardiovascular system, inflammation levels throughout the body. Any one of those things could affect the brain.

“Most likely, the effect of obesity on the brain is related to not just one cause but a combination of causes,” Gunstad says.