Intermittent Fasting Shows Significant Effects on Gut, Brain

Scientists in China have uncovered significant findings in the battle against obesity, demonstrating that intermittent calorie restriction (IER) results in meaningful changes in both the gut and the brain.

The study, which involved 25 obese volunteers over a 62-day period, employed a regime of intermittent energy restriction—carefully controlling calorie intake with periods of relative fasting.

Participants experienced an average weight loss of 7.6 kilograms (16.8 pounds), or 7.8 percent of their body weight. Additionally, researchers observed changes in brain regions associated with obesity and in the composition of gut bacteria.

"Here we show that an IER diet changes the human brain-gut-microbiome axis," said Qiang Zeng, a health researcher from the Second Medical Center and National Clinical Research Center for Geriatric Diseases in China, when the results were published in December 2023.

"The observed changes in the gut microbiome and in the activity in addiction-related brain regions during and after weight loss are highly dynamic and coupled over time," Zeng added.

While the exact mechanisms driving these changes remain unclear, the study confirms the close link between the gut and brain. It suggests that targeting specific brain regions could potentially help regulate food intake.

Functional magnetic resonance imaging (fMRI) scans revealed changes in brain activity in areas critical for appetite and addiction regulation, including the inferior frontal orbital gyrus. Furthermore, stool samples and blood measurements indicated that shifts in gut microbiome were associated with these brain regions.

Notably, bacteria such as Coprococcus comes and Eubacterium hallii were negatively associated with activity in the left inferior frontal orbital gyrus, a region involved in executive function, including willpower over food intake.

"The gut microbiome is thought to communicate with the brain in a complex, two-directional way," said Xiaoning Wang, a medical scientist from the State Clinic Center for Geriatrics in China. "The microbiome produces neurotransmitters and neurotoxins that reach the brain through nerves and blood circulation. In return, the brain controls eating behavior, while nutrients from our diet alter the gut microbiome composition."

With over a billion people worldwide affected by obesity, which raises the risk of numerous health issues such as cancer and heart disease, understanding the brain-gut connection could significantly enhance efforts to prevent and reduce obesity.

"The next question to be answered is the precise mechanism by which the gut microbiome and the brain communicate in obese people, including during weight loss," said Liming Wang, a biomedical scientist from the Chinese Academy of Sciences. "What specific gut microbiome and brain regions are critical for successful weight loss and maintaining a healthy weight?"