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New research suggests that a fasting-style diet can rapidly reshape the link between our brains and our guts. In a small, controlled trial, obese volunteers who followed an intermittent energy restriction (IER) regimen for 62 days lost significant weight while showing measurable shifts in brain activity and gut bacterial composition—changes that appear to track together over time.
Study design and headline results
Researchers in China enrolled 25 adults classified as obese and put them on an IER program—periods of reduced calorie intake interspersed with normal eating—over roughly two months. By the end of the 62-day protocol the group lost an average of 7.6 kilograms (16.8 pounds), equal to about 7.8% of body weight. The team combined weight measurements with functional magnetic resonance imaging (fMRI), stool sampling and blood tests to map how the brain and gut responded during weight loss.
The study, published in Frontiers in Cellular and Infection Microbiology, found that appetite- and addiction-related brain regions showed dynamic changes in activity during the diet. At the same time, the gut microbiome shifted in composition, with particular bacterial species linked to specific brain responses.
Which brain areas and microbes changed?
fMRI scans highlighted altered activity in regions implicated in reward processing, impulse control and appetite regulation—most notably the left inferior frontal orbital gyrus, an area associated with executive function and inhibitory control. On the microbiome side, stool analyses pointed to changes in taxa such as Coprococcus comes and Eubacterium hallii. Intriguingly, levels of these bacteria were negatively associated with activity in the left inferior frontal orbital gyrus: higher abundance of the bacteria correlated with lower activation in that brain region.
Two-way communication: gut signals and brain responses
Scientists have long suspected a bi-directional dialogue between gut microbes and the brain. Microbes can produce neurotransmitters and metabolites that travel via the bloodstream or through neural pathways, potentially altering mood, cravings and appetite. Conversely, brain-driven changes in behavior—like the timing and amount of food consumed—reshape the gut environment and the microbes that thrive there.
"Here we show that an IER diet changes the human brain-gut-microbiome axis," said Qiang Zeng, one of the lead health researchers. "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."
Implications for treating obesity
More than a billion people worldwide are estimated to live with obesity, a condition that raises risks for heart disease, diabetes and some cancers. These new findings hint that dietary strategies such as intermittent energy restriction do more than reduce calories: they may alter the neural circuits that govern craving and impulse control while simultaneously reshaping the microbial signals those circuits receive.
Understanding which specific microbes and brain regions are essential for successful, long-term weight control could open novel intervention paths. For example, targeted probiotics, microbial-derived metabolites or neuromodulation approaches might be used in tandem with dietary changes to reinforce healthy eating behaviors.
What remains unknown
Critical questions remain. The study cannot yet determine causality—does the microbiome drive brain changes, or do shifts in brain activity alter the gut community? And which microbes are most important for sustaining weight loss over months or years?
"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 from the Chinese Academy of Sciences. "What specific gut microbiome and brain regions are critical for successful weight loss and maintaining a healthy weight?"
Expert Insight
Dr. Rachel Meyers, a behavioral neuroscientist at a university medical center, notes: "This study strengthens the idea that diet-induced changes are systemic. Intermittent energy restriction appears to reconfigure both the microbial milieu and the neural circuits that influence eating. That dual effect could be why some people find fasting-style diets especially effective—at least in the short term. But translating these findings into long-term therapies will require larger, longer trials and a focus on which microbial shifts are beneficial versus merely associated with weight loss."
Next steps for researchers and clinicians
Future work should expand participant numbers, include control diets, and track changes over longer periods. Integrating metabolomics—measuring microbial metabolites in blood—and causal experiments (for example, transplanting human-derived microbes into animal models) would help reveal mechanisms. Clinicians may already consider intermittent fasting as one tool in a broader, personalized weight-management toolkit, but the research underscores the potential for combining dietary strategies with microbiome-informed therapies.
The research provides a promising glimpse into how structured eating patterns can produce coupled changes in the gut microbiome and the brain—an axis that may prove vital in next-generation obesity treatments.
Source: sciencealert
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