Terry Davidson, CAS
New research by Terry Davidson, director of AU’s Center for Behavioral Neuroscience, indicates that diets high in saturated fat and refined sugar may cause changes in the brains of obese people. These changes in turn can fuel overconsumption of those same foods—a cycle that could explain why obesity is so difficult to overcome.
Davidson’s research, described in “The Effects of a High-Energy Diet on Hippocampal-Dependent Discrimination Performance and Blood-Brain Barrier Integrity Differ for Diet-Induced Obese and Diet-Resistant Rats,” published in the journal Physiology and Behavior, focuses on the hippocampus—the area of the brain responsible for memory and learning. Davidson and his team trained rats given restricted access to low-fat “lab chow,” testing them on two problems—one that measured hippocampal-dependent learning and memory and one that did not. Once the training phase was completed, the rats were split into two groups: one had unlimited access to the low-fat lab chow, the other was given high-energy food containing saturated fat.
When both groups were retested, the now-obese rats performed much more poorly than their non-obese counterparts on the problem designed to test hippocampal-dependent learning and memory. Interestingly, the non-obese group included those from both the low-fat and high-energy diet groups.
However, this wasn’t a matter of some having a super-high metabolism that allowed them to eat large amounts of the high-energy food and remain a reasonable weight, Davidson says. “Those without blood-brain barrier and memory impairment also ate less of the high-energy diet,” he notes. “Some rats and some people have a lower preference for high-energy diets. Our results suggest that whatever allows them to eat less and keep the pounds off also helps to keep their brains cognitively healthy.”
The hippocampus is also responsible for suppressing memories. If Davidson’s findings apply to people, it could be that a diet high in saturated fat and refined sugar affects the hippocampus’s ability to suppress unwanted thoughts, such as those about high-calorie foods. This could make it more likely that an obese person would consume those foods and not be able to stop at a reasonable serving.
“What I think is happening is a vicious cycle of obesity and cognitive decline,” Davidson explains. “The idea is, you eat the high-fat, high-calorie diet and it causes you to overeat because this inhibitory system is progressively getting fouled up. And unfortunately, this inhibitory system is also for remembering things and suppressing other kinds of thought interference.”
Davidson’s findings are compatible with other studies detecting a link between human obesity in middle age and an increased likelihood of developing Alzheimer’s disease and other cognitive dementias later in life.
“We are trying to figure out that link,” Davidson says. “We have compelling evidence that overconsumption of a high-fat diet damages or alters the blood-brain barrier. Now we are interested in the fact that substances that are not supposed to get to the brain are getting to it because of this breakdown. You start throwing things into the brain that don’t belong there, and it makes sense that brain function would be affected.”
In fact, two papers by Davidson, soon to appear in the journals Neurobiology of Learning and Memory and Neuroscience, describe how brain pathologies that produce cognitive dementias in old-age may have their origins in early childhood. Davidson is embarking on a research project with colleagues in the School of Education, Teaching, and Health that will attempt to identify subtle cognitive deficits in school children that are produced by these pathologies. Davidson says, “It is our hope that the earlier such problems can be diagnosed, the more effective will be treatments that aim to alleviate them.”
AU Biologist Discovers New Crab Species
Areopaguristes tudgei—that’s the name of a new species of hermit crab recently discovered on the barrier reef off the coast of Belize by AU biology professor Christopher Tudge. Differentiated from others in its genus by such characteristics as the hairs growing on some of its appendages, Tudge’s tiny namesake joins the list of about three million known species.