Scientists from Imperial College in London and the University of Glasgow have found that eating a type of food supplement that is based on a molecule produced by bacteria in the gut may be able to reduce cravings for high-calorie foods.
During the study, scientists asked 20 volunteers to consume a milkshake that either had an ingredient known as inulin-propionate ester, or a type of fiber known as inulin. Studies in the past had shown that bacteria in the gut releases a compound called propionate when they digest the fiber inulin, which signals the brain to reduce the body’s appetites. The inulin-propionate ester supplement releases far more propionate in the intestines than the inulin did on its own.
After drinking their milkshakes, the participants were given MRI scans while being shown pictures of different low and high calorie foods which included salad, fish and vegetables or chocolate, cake and pizza. The team discovered that when volunteers drank the milkshake with the inulin-propionate ester they showed far less activity in areas of the brain that are linked to reward when looking at high calorie foods. These areas of the brain, the caudate and the nucleus accumbens have been linked to food cravings and the motivation to desire food. Volunteers were also asked to rate just how appealing they found the foods they were shown. Those who had ingested inulin-propionate ester rated the high calorie foods to be less appealing.
During the second part of the study which has been published in the July edition of the American Journal of Clinical Nutrition, volunteers were given a bowl of pasta with tomato sauce and asked to eat as much as they liked. When participants were given inulin-propionate ester they ate about 10 percent less pasta.
Previous research that was published by the team in 2013 found that overweight volunteers who added the inulin-propionate ester supplement to their food each day gained less weight over a six month period when compared to those who only added inulin to their meals.
Senior author of the study, Professor Gary Frost from the Department of Medicine at Imperial said their previous findings showed that people who ate this ingredient gained less weight but they did not know why. The new 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.
He went on to say that eating enough fiber to naturally produce similar amounts of propionate is very difficult. The amount of inulin-propionate ester used in the study was 10 grams which previous studies have shown increases natural propionate production by about 2.5 times. In order to get the same increase from fiber alone, one would have to eat about 60 grams a day.
Claire Byrne, a PhD researcher from the Department of Medicine explained that using inulin-propionate ester as a food ingredient may be able to help prevent weight gain. She said adding it to foods could reduce the urge to consume high calorie foods. She also says that some people’s gut bacteria may naturally produce more propionate than others which is why some people seem to be predisposed to gaining weight.
Co-author of the study, Dr. Tony Goldstone says that this study adds to our previous brain imaging studies in people who have had gastric bypass surgery for obesity. These show that altering how the gut works can change not only appetite in general, but also change how the brain responds when they see high-calorie foods and how appealing they find the foods to be.
Dr. Douglas Morrison, author of the paper from the Scottish Universities Environmental Research Centre at the University of Glasgow says they have developed inulin-propionate ester to investigate the role of propionate produced by the gut microbiota in human health. 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 fiber is important for healthy living.