Eating foods high in fat—tasty french fries, for example—changes the populations of bacteria innate to flora in the digestive tract, or gut, and alters signaling to the brain, according to a recent study co-authored by a UGA researcher. The result: People no longer recognize that they are full, which can cause overeating, a leading cause of obesity.
“We change our brain circuits by eating unbalanced foods, and we also induce the inflammation in brain regions responsible for feeding behavior,” said study co-author Krzysztof Czaja, an associate professor of neuroanatomy in the UGA College of Veterinary Medicine. “Those reorganized circuits and inflammation may alter satiety signaling.”
The findings from this study, which was conducted by researchers at UGA, Washington State University and Binghamton University, were presented last month in Denver at the 23rd annual meeting of the Society for the Study of Ingestive Behavior.
So what happens to the microbiota in the intestines when someone switches to a high-fat diet? Czaja likens the microscopic phenomenon to how a sudden significant shift in temperature might impact the people who live in the affected area: Some people will be fine. Others will become ill.
“In the regular physiological state, many different strains of bacteria live in a balanced environment in our intestinal tract,” Czaja said. “They don’t overpopulate. There are little shifts, but in general this population is quite stable.”
When a different diet is introduced, there is an immediate effect.
“Suddenly, different nutrients are changing the microenvironment in the gut, and some bacteria begin to overpopulate,” he said. “Some sensitive bacteria begin to die, and some populations may even vanish. So, introducing a significant change in the gut microenvironment triggers a cascade of events that leads to this population switch.”
All of these changes result in miscommunication between the gut and the brain, he said. It is not yet known whether this change is permanent, but Czaja and his colleagues plan to address this question in the future.
Throughout the history of mankind, until just a few decades ago, Czaja said, the human body was used to foods derived from natural and whole sources, rather than artificial and highly processed.
“We should be aware that on a high-fat (and high-carbohydrate) diet, balance in the intestinal microbiota and gut-brain communication—which was developing over thousands and thousands of years in humans and animals—has been interrupted by the introduction of modified foods,” he said. “This leads to the confused brain and inappropriate satiety feedback and results in obesity.”