If you're having trouble shaking your cravings for doughnuts, hamburgers and pizza, the key to curbing them could come from a new supplement based on a compound released by gut bacteria. The appetite-suppressing supplement developed by scientists from England and Scotland is called inulin-propionate ester and was found to only affect cravings for high calorie foods.

As its name suggests, the inulin-propionate ester supplement developed by the researchers from the Imperial College in London and the University of Glasgow in Scotland is made from a type of fiber called inulin that contains propionate, a molecular compound released in the intestines by gut microbiota that sends signals to a person's brain to make them feel full.

The digestion of inulin on its own has previously been shown to trigger the release of appetite-suppressing propionate by bacteria in the gut, but the team discovered that eating inulin-propionate ester resulted in the release of much more propionate in the intestines than inulin alone, and therefore had a much greater effect on appetite and weight gain. The team's latest study has now shed light on the reasons for this.

Scientists obtained the data for their supplement study in two parts. First, they gathered a group of volunteers who were willing to drink a tasty milkshake containing either the new supplement or a simple dose of inulin. Then they conducted MRI scans on the subjects' brains while showing them pictures of various foods.

They found that volunteers who had digested the new supplement exhibited less activity in parts of the brain linked to reward when they saw pictures of food containing a high number of calories. The volunteers were also asked to rate the foods they were shown and the high calorie foods received lower marks from participants who had taken the new supplement rather than inulin alone.

The second test asked the same group of volunteers to enjoy a never-ending bowl of pasta covered in tomato sauce until they felt satisfied. The volunteers who unknowingly took the inulin-propionate ester supplement in the previous experiment ate 10 percent less food compared to those volunteers who had only taken an inulin supplement.

"Our previous findings showed that people who ate this ingredient gained less weight – but we did not know why," says the senior author of the study from Imperial, Professor Gary 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."

"The amount of inulin-propionate ester used in this study was 10 g, which previous studies show increases propionate production by 2.5 times," added Professor Frost. "To get the same increase from fiber alone, we would need to eat around 60 g a day. At the moment, the UK average is 15 g."

The researchers theorize that some people's gut bacteria may naturally produce more propionate than others, which may help explain why some people seem naturally predisposed to gaining less weight than others. They add that adding the inulin-propionate ester to foods could help prevent weight gain by reducing people's appetite for high calorie foods.

The microbes found in our gut could also play a big role in controlling our ravenous appetites, according to a study published last year. The study showed that gut microbes produced by bacteria such as E.coli can reduce food cravings in mice and rats by activating neurons responsible for controlling appetites. Researchers who conducted the study found that E.coli started producing the proteins after a 20-minute period, the same amount of time it takes a person to feel full after they've eaten.

The study was published in the American Journal of Clinical Nutrition.