Scientists trying to tackle the ongoing obesity crisis have made an important discovery: intermittent calorie restriction produces profound changes in both the gut and the brain that could open up new options for maintaining a healthy weight.
Chinese researchers studied 25 volunteers classified as obese over a 62-day period during which they participated in an intermittent energy restriction (IER) program, which involves carefully controlling caloric intake and several days of relative fasting.
Not only did study participants lose an average of 7.6 kilograms (16.8 pounds), or 7.8 percent of their body weight, but there was also evidence of changes in activity in obesity-related areas of the brain and in the composition of gut bacteria.
“Here we show that the IER diet alters the brain-gut-microbiota axis in humans,” Zhang Zeng, a health researcher at China Second Medical Center and the National Clinical Research Center of Geriatrics, said when the results were published in December 2023.
“The changes in gut microbiota observed during and after weight loss and activity in addiction-related brain regions are highly dynamic and coupled over time.”
It’s not clear what causes these changes, or whether the gut influences the brain or vice versa, but we do know that the two are closely connected, so by treating specific areas of the brain, it may be possible to control food intake.
The changes in brain activity found by functional magnetic resonance imaging (fMRI) scans were found in areas known to be important in regulating appetite and addiction, including the inferior frontal orbital gyrus.
Furthermore, changes in the gut microbiota, analyzed by stool samples and blood measurements, were associated with specific brain regions.
For example, the bacteria Coprococcus comes and Eubacterium hali were found to be negatively correlated with activity in the left inferior frontal orbital gyrus, an area involved in executive functions such as willpower regarding food intake.
“The gut microbiota is thought to have a complex, bidirectional communication with the brain,” said Wang Xiaoning, a medical scientist at the China National Center for Geriatrics.
“The gut microbiota produces neurotransmitters and neurotoxins that reach the brain via the nervous system and blood circulation. The brain in turn controls feeding behavior, and the nutrients we ingest in our diet change the composition of our gut microbiota.”
It is estimated that over one billion people worldwide are obese, which is linked to an increased risk of a range of health problems from cancer to heart disease. A better understanding of how the brain and gut are interdependent could make a big difference in effectively preventing and reducing obesity.
“The next question to be answered is the exact mechanism by which the gut microbiota and the brain communicate in obese people, including during weight loss,” said Wang Liming, a biomedical scientist at the Chinese Academy of Sciences.
“What specific gut microbiomes and brain regions are important for successful weight loss and maintaining a healthy weight?”
This research was published in Frontiers in Cellular and Infection Microbiology.
A previous version of this article was published in December 2023.
