With recent studies revealing that one in five children born at the start of the millennium was obese by the age of 11 and that obesity can knock eight years off life expectancy, the discovery of a chemical that makes people feel full could become a game changer in public health.
Researchers from Imperial College London and the University of Glasgow have discovered that adding a by-product of fibre digestion to foods makes them more filling, causing people to eat less and slow weight gain. Increased dietary fibre has long been linked to reduced appetite and weight loss, but the gastrointestinal side effects associated with the large amounts required make this an unpopular solution.
The scientists recognised that proprionate – a short chain fatty acid (SCFA) produced by the microbial fermentation of dietary fibre in the colon – is influential in causing satedness after eating. It triggers the release of anorectic hormones from the gut that are involved in the short-term signal of satiety to the appetite centres of the brain.
Because orally administered SCFAs are unpalatable and rapidly absorbed in the small intestine, the researchers developed a carrier molecule with proprionate bound by an ester bond to the carbohydrate inulin. The majority of propionate in this inulin-propionate ester (IPE) is only released when the inulin polymer is fermented by the colonic microbiota, thus providing targeted colonic delivery.
Volunteers were given either IPE or inulin powders to mix with food in the study published in Gut and allowed to eat as much as they liked from a buffet. Those given IPE ate 14 per cent less on average and had higher concentrations of appetite-reducing hormones in the blood. And volunteers who had IPE powder added to their food over a 24-week period gained less weight than those given inulin. Of the 24 given inulin, six had gained more than 3 per cent of their original body weight, while only one of the 25 given IPE had done so.
The researchers have suggested that IPE could be added to smoothies or bread. They propose that the product could be used to tackle the reported average 0.3 – 0.8 kg/year weight gain in middle-aged adults. This gradual long-term weight gain can be the result of a small habitual positive energy balance of 50–100 kcal/day.