Writing in the American Journal of Clinical Nutrition, scientists discovered that the molecule, inulin-propionate ester (IPE), exhibited a more powerful appetite suppressant effect when compared to another type of fibre called inulin.
MRI brain scans of subjects consuming IPE revealed a decrease in activity in brain regions linked to reward. This was seen only when looking at foods high in calories.
The study sought to further understand the signals communicating information about current energy balance to the brain to maintain energy needs.
It also illustrates how diet, the gut microbiome and health are inextricably linked, adding to the understanding of how feeding gut microbes with dietary fibre may be important for health.
Mounting evidence suggests that metabolites produced by gut microbiota may affect central appetite regulation.
Fermentation products generated by the gut bacteria include a selection of short-chain fatty acids (SCFAs) like acetate, butyrate and propionate.
But it is the propionate produced that is the subject of much excitement. Previous studies have demonstrated that IPE releases much more propionate in the intestines than inulin.
Weight management
The researchers believe that consuming enough fibre either through supplementation or through food could form a simple strategy to help people maintain a healthy weight.
However, Professor Gary Frost, senior author of the study from the department of medicine at Imperial College London, said that eating enough fibre to naturally produce propionate amounts that rivals IPE would be difficult.
"The amount of IPE used in this study was 10 g, which previous studies show increases propionate production by 2.5 times,” he said.
“To get the same increase from fibre alone, we would need to eat around 60 g a day. At the moment, the UK average is 15 g."
The use of supplementation in decreasing Body Mass Index (BMI), hereditary risk of obesity, and prospective weight gain has been the subject of much research.
Digestion-resistant starch, a fermentable dietary fibre, has been used to good effect in altering activation of brain regions involved in the appetite regulation of rodents.
In addition, the supplementation of nondigestible carbohydrates (NDCs) such as oligofructose and β-glucan also reduces energy intake and weight gain in animal models.
IPE-containing milkshakes
Along with Imperial College, scientists from the University of Glasgow gave 20 volunteers a milkshake containing either IPE or inulin.
The subjects then underwent an MRI scan, where they were shown pictures of various low or high calorie foods such as salad, fish and vegetables or chocolate, cake and pizza.
Consumers of the IPE milkshake had less brain activity in response to high-calorie foods primarily in the caudate and the nucleus accumbens area of the brain, already identified as a region responsible for food urges and cravings.
The study then asked the volunteers to consume as much pasta and tomato sauce as they liked. Those that drank the IPE milkshake ate 10% less pasta when compared to the inulin milkshake drinkers.
"Our previous findings showed that people who ate this ingredient gained less weight but we did not know why,” said Frost.
“This study is filling in a missing bit of the jigsaw and shows that this supplement can decrease activity in brain areas associated with food reward at the same time as reducing the amount of food they eat."
Future potential
Dr Claire Byrne, also from Imperial’s Department of Medicine, explained that using IPE as a food ingredient may help prevent weight gain.
"If we add this to foods it could reduce the urge to consume high calorie foods,” she said.
“Some people's gut bacteria may naturally produce more propionate than others, which may be why some people seem more naturally predisposed to gain weight.”
Frost added that future research would concentrate on understanding the impact of fibre when added to certain foods.
“This is ongoing,” he explained, “but our initial understanding is it can be added to a wide range of foods".
“However, I think adding large amounts of fibre to food changes taste and consistency of the food, which is undesired.”
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.115.126706
“Increased colonic propionate reduces anticipatory reward responses in the human striatum to high-energy foods.”
Authors: Gary Frost et al