New Study Finds that Obesity Can Hurt the Brain and Memory as Well as the Body
Diets high in saturated fats and sugars affect the parts of the brain related to memory and cravings
Medicine has known for a long time about the harmful effects that being overweight can have on the body. Blood pressure and cholesterol are affected, and the risk of developing diabetes goes up. Now, reports NPR, a new study has found that the brain can also be hurt by the extra weight.
Terry Davidson is a psychologist and the director of the Center for Behavioral Neuroscience at American University. According to him, diets that are high in saturated fats and sugars—which are known as the "Western diet"—affect the areas of the brain that are related to memory and that make it more likely that people will crave the unhealthy food.
Davidson didn't start off studying people's diets. He wanted to learn more about a part of the brain called the hippocampus, which plays a very large role in memory. Specifically, he was trying to determine what each part of the area does.
To try to figure this out, he studied rats with very specific kinds of damage to the hippocampus in their brains and looked at what happened to them. In doing so, however, he saw something odd: the rats whose brains were damaged would pick food up more often than the other rats, but would then drop it after eating only a little bit of it.
The rats, Davidson realized, didn't know that they were full. He believes that human brains may experience something similar when a person's diet is high in fat and sugar. He noted the existence of a cycle of bad diets and changes to the brain, referring to a study published in 2015 in which obese children did worse than children who were not overweight on memory tasks designed to test the hippocampus area.
If our brain is hurt by that type of diet, Davidson says, "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."
More and more evidence supports this theory. Back in July, the Cambridge Centre for Ageing and Neuroscience published its findings on how people who are obese have less white matter in their brains than their non-overweight peers—as if their brains were 10 years older than they actually were. And University of Arizona researchers recently published their own study, whose findings support the leading theory that inflammation that affects the brain is linked to high body mass.
Scientists believe that if we can understand the relationship between obesity and the brain and memory, we might be able to use it to stop people from reaching that point to begin with.
University of Cambridge psychologist Lucy Cheke recently published a study that she says helps to point the way in doing that. The researchers requested that both obese and thin people perform a kind of memory task like a virtual treasure hunt. They had to hide something in a scene across several different sessions at a computer. Then the researchers asked them what it was that they hid, where they hid it, and in which session they did so.
In each part of the experiment, the obese participants did between 15 and 20 percent worse than their thin counterparts, a finding that confirmed observations made by other researchers in rodents.
"This really picks apart spatial, item and temporal memory, as well as, crucially, the ability to integrate them," which, according to Cheke, is "one of the most fundamental aspects of memory."
If a person is obese, she says, they might be "10 to 15 to 20 percent more likely to not quite remember where [they] put [their] keys."
There are ways in which people can compensate, however, as Davidson illustrated.
"Let's say I had a kid," he said, "and I gave him a high-fat diet and he showed hippocampal dysfunction. That kid may not do worse in school."
However, he added, the processes that help kids do well in school may not be working correctly. When this happens, the child has to work harder and be more motivated and in general would "have a tougher go of it."
According to Cheke, as the relationship between obesity and the brain grows as a field of research, we may figure out more ways to fight obesity. However, as noted by John Gunstad, professor and director of the Applied Psychology Center at Kent State University, we don't know exactly how the brain is affected by obesity, even though we now know there is a connection.
Gunstad noted that many changes happen in the body when a person is overweight: blood sugar, the cardiovascular system, and inflammation levels are all affected. Any of these things might have an effect on the brain.
"Most likely, the effect of obesity on the brain is related to not just one cause but a combination of causes," Gunstad said.
Davidson is studying how to break the cycle between the Western diet, obesity, and changes to the brain. He believes that it is clear that obesity affects the brain.
"It's surprising to me that people would question that obesity would have a negative effect on the brain, because it has a negative effect on so many other bodily systems," he said, adding, why would "the brain would be spared?"