According to Science Alert, the research team had shown that taking in inulin, a type of dietary fiber, can make gut bacteria increase their production of a molecule called propionate. This molecule is produced when a person is full, and the brain is then informed that the person has had enough to eat.  

The researchers from the Imperial College London and the University of Glasgow modified inulin so that it also contains propionate, producing a compound called inulin-propionate ester. This compound triggers gut bacteria to produce more propionate of up to 2.5 times.    

In their test, the researchers gave 20 volunteers milkshake, some with just regular inulin and some with 10 grams of inulin-propionate ester. They then showed the volunteers pictures of different kinds of food, such as those with low calories like salads and those with high calories like chocolate. This was done while the subjects were under an MRI scanner, with the researchers paying attention to the caudate and the nucleus accumbens - the reward regions of the brain believed to be linked to the motivation to want food.    

The researchers found that, when shown high-calorie foods, those who drank the shake with inulin-propionate ester exhibited less activity in the reward regions of their brains than those who only took regular inulin. The participants who took the compound also said that the high-calorie foods were less appealing. The study suggests that the volunteers had less craving for unhealthy types of food.  

The second part of the experiment involved asking the volunteers to eat as much pasta with tomato sauce as they wanted. Those who drank the supplement ate 10 percent less than the rest of the group.  

The team's previous study saw that those who took the supplement gained less weight, but they still have not figured out why. It could also be that the gut bacteria in some people are able to produce more propionate, which is why they are able to keep their weight down.  

"We developed inulin-propionate ester to investigate the role of propionate produced by the gut microbiota in human health," said Dr. Douglas Morrison, author of the paper from the University of Glasgow, according to Imperial College London. "This study illustrates very nicely that signals produced by the gut microbiota are important for appetite regulation and food choice. This study also sheds new light on how diet, the gut microbiome and health are inextricably linked adding to our understanding of how feeding our gut microbes with dietary fibre is important for healthy living."  

The study, titled "Increased colonic propionate reduces anticipatory reward responses in the human striatum to high-energy foods," was published in July edition of the American Journal of Clinical Nutrition, but it could still take a while before the supplement becomes available. The results of the study, according to Science Alert, need to be replicated and links between cravings and the compound need to be firmly established.