Gut bacteria produce an appetite suppressant than can strengthen the effect of an exercise-based weight loss program.
The many health benefits of regular exercise are well known. However, its impact on weight loss is less clear, as exercise increases appetite, potentially resulting in an increased calorie intake.
A new study appearing in the journal Metabolism presents a possible solution.
The research comes from the Scottish Universities Environmental Research Centre, the Universities of Glasgow and the West of Scotland, and Imperial College in London, all of which are in the United Kingdom.
It suggests that adding a certain appetite-suppressing supplement to moderate exercise increases the likelihood of weight loss, even without a change of diet.
The Biotechnology and Biological Sciences Research Council provided funding for this research.
A fascinating supplement
The study explored a supplement called inulin-propionate ester (IPE).
Propionate is a short-chain fatty acid produced in the digestion of dietary fiber by gut microbes. It is a natural and effective appetite suppressor.
Propionate breaks down quickly in the body, so to strengthen its effect, scientists have chemically bound it to inulin. This is a fiber common to garlic, Jerusalem artichoke, chicory, and onion. The result is IPE.
As corresponding study author Douglas Morrison notes, "There's a great deal of interest at the moment in how our gut microbiota affects our health and well-being."
The scientists' previous research established that the use of IPE as a dietary supplement increased the rate at which the body oxidizes, or burns, fat while at rest.
The research also found that IPE suppresses the urge to consume high calorie foods. As an example, those who the researchers offered all the pasta they could eat wound up eating 10% less than they usually would.
Their new study has revealed that IPE can enhance the weight loss effects of a moderate exercise program without requiring dietary changes.
As Morrison explains, "What we've been able to show for the first time is that this latter effect continues when exercise is added to regular IPE intake." The study did not examine the effectiveness of a weight loss diet plus exercises plus IPE.
The trial consisted of 20 women aged 25–45. Each had a body mass index (BMI) greater than 25. The trial lasted for 4 weeks.
The team divided the participants into two groups of 10. Both groups participated in moderate exercise programs.
One group received a supplement of IPE, and the other received a placebo supplement comprising cellulose. All participants maintained their normal eating patterns throughout the trial.
The researchers measured each person's resting fat oxidation levels both before and after the trial using blood and gas samples. They collected these before breakfast, after breakfast, and after lunch.
The participants who exercised while taking the placebo exhibited no change to their fat oxidation levels after the trials.
The group taking the IPE, however, showed a significant increase in the burning of fat at rest, even 7 hours after their most recent dose of IPE.
Limitations of the study
The new study was small and its duration brief, so its conclusions require additional verification.
Study co-author Dalia Malkova says, "While these initial results are promising, we should stress that there are limitations to this study, which was conducted with a small group over just  weeks."
"For example, we can't yet draw any conclusions about how the increased fat oxidation, combined with exercise, might affect participants' body composition and body mass."
The researchers are seeking funding for further trials of IPE, involving more people and for a longer period of time.