Gut-brain axis: Prebiotics may alter food decision-making in overweight adults

16 Oct 2023 --- New research indicates that consumption of high-dose dietary prebiotics may reduce reward-related brain activation in response to high-calorie food. The German-based researchers suggest that functional microbial changes underlie this altered brain response to high-calorie food.

In the clinical trial, the research team used advanced neuroimaging, next-generation sequencing of gut bacteria and combined analyses of potential metabolic pathways. 

The 59 clinical trial participants, all overweight and following an omnivorous diet, consumed 30 g of inulin — a prebiotic from chicory root — daily for two weeks. In MRI experiments, the participants were asked to evaluate food options while researchers assessed their gut bacteria composition. 

“Our findings might imply that non-invasive interventions that change the gut-brain axis signaling (as, for example, in our case, prebiotics) could potentially change brain functions, including eating behavior,” co-author Dr. Veronica Witte, a scientist at the University of Leipzig Medical Center, tells Nutrition Insight. 

“In the long term, this may help to reach or maintain healthier weight status and thereby adding to preventive or therapeutic options in, for example, obesity research.” 

Study set up 
Through MRI imaging, the researchers showed participants pictures of food and asked how much they desired the meals presented. After the experiment, participants received their highest-rated dish and were asked to consume it. 

Consumption of prebiotics may reduce reward-related brain activation in response to high-calorie food.The research team repeated this MRI examination four times, before and after participants consumed their prebiotic and those in the placebo phase. In this phase, participants consumed a preparation with identical energy density but without prebiotics. 

After consuming the prebiotic fiber, there was comparatively less activation of reward-related brain areas when they evaluated high-calorie foods. At the same time, the researchers also found a shift in gut bacteria composition. 

“The results suggest a potential link between gut health and brain function, in this case, food decision-making,” says Witte. 

Gut-brain axis 
Moreover, the researchers analyzed participants’ fasting blood samples for gastrointestinal hormones, glucose, lipids and inflammatory markers while measuring the gut microbiota and their metabolites — short-chain fatty acids (SCFA) — in stool samples. 

Fasting blood levels remained essentially unchanged, explain the researchers, but they found significant shifts in participants’ microbiome with increases in SCFA-producing Bifidobacteriaceae and changes in functional signaling pathways after prebiotic consumption. 

In addition, changes in brain activation correlated with changes in Actinobacteria microbial abundance and associated activity previously linked with SCFA production.

At the same time, the researchers note that the current data does not allow them to conclude the changes in brain responses from the prebiotic treatment were beneficial for behavioral control. Previous studies indicate that a neutral reaction during MRI scanning predicted behavioral change in reward-related areas. 

Future research 
Witte explains that further studies are needed to investigate whether treatments that alter the microbiome could open up new avenues for less invasive approaches to preventing and treating obesity. 

“We’re currently running another six-month study with people living with overweight and obesity to see if longer applications of prebiotic intake would lead to similar neuronal correlates and even behavioral and weight changes (i.e., less craving for high-caloric food).” 

The study participants consumed inulin daily, obtained from chicory root.For the upcoming study, Witte details, the researchers aim to recruit 90 participants between 18-60 years old. These will be randomized into three study groups: one consuming a prebiotic 30 g inulin intake/day, one placebo group and one partaking in psycho-educative group sessions to improve eating behavior.

She continues that a better understanding of the underlying mechanisms between the microbiome, gut and brain could help develop new strategies to promote healthier eating habits in at-risk people.

“It is also still difficult to measure the mediating mechanisms in humans. For example, we implement blood sampling before and after a meal to further look at blood markers, such as short chain fatty acids.”

Prebiotic fibers  
Prebiotic, indigestible fibers are found in plant-derived foods such as onions, leeks, artichokes, wheat, bananas and chicory root. 

These fibers support gut health by promoting the growth and activity of beneficial gut bacteria. 

Recent research also indicated that chicory root fiber can promote the growth of Bifidobacteria in the gut. Fibers from this root have been shown to positively impact bowel functions, the immune system, weight and blood sugar management. 

By Jolanda van Hal