An ingredient that can be added to food to make it more filling may be less effective at preventing weight gain in young people but could help them build more muscle, new research suggests.

In a new paper published in eClinicalMedicine, researchers from U.K. universities report on the results of a randomized trial that expands on previous tests of the effectiveness of a compound called inulin-propionate ester, or IPE, to promote weight loss and suppress appetite.

IPE contains propionate, a short-chain fatty acid produced in the human body when dietary fiber is fermented by gut microbes. When propionate is introduced into the body in larger quantities than could be ingested through a normal diet in the form of IPE, it stimulates the gut to release hormones which can affect the brain to reduce feelings of hunger.

Previous research from the same team showed that older participants with a mean age of 54 who took IPE supplements actually lost weight, had lower fat mass and intra-abdominal fat, and found high-energy foods less appealing than those who took a control substance called inulin, a type of fiber.

The results of the research are part of a wider study called iPREVENT, The new study, which is longer-term than previous studies, shows some differences in the ways that younger people’s bodies reacted to IPE supplements.

Over the course of the 12-month study, 270 participants across Glasgow and London aged 20 to 40 were divided into groups consuming either IPE or inulin.

The trial revealed no significant difference in weight gain between the IPE and control groups over the course of the study. The IPE group saw no reduction in fat mass or body weight, and blood glucose levels also rose marginally in the IPE group, though within normal ranges.

However, the researchers found a significant increase in fat-free mass in the participants given IPE that wasn’t accounted for by a change in physical activity among either group.

Professor Douglas Morrison of the Scottish Universities Environmental Research Center (SUERC) and the University of Glasgow, is one of the paper’s corresponding authors. He said, “Preventing weight gain in early life can have significant health benefits later in life—it’s better to maintain a healthy weight throughout life than to try to lose weight as an older adult, although reaching a healthy weight at any age is beneficial.

“Our previous studies had shown that older people could benefit significantly from adding IPE supplements to their diets, and we were keen to explore in this study whether the results would be similar in younger people. Increasing fat-free mass is an interesting and unexpected result which may warrant further study, because building muscle can help improve metabolic health.”

The researchers note in the paper that the results may have been affected by the COVID-19 pandemic, which occurred during the study and may have influenced the diets and lifestyles of the participants. They also highlight the possibility that the dose of IPE, which produced beneficial effects in older people, may not have had the same effect on the metabolisms of the younger participants.

Professor Gary Frost of Imperial College London, the lead investigator in London, said, “These findings highlight the complexity of weight gain prevention, particularly in younger adults, where behaviors and energy intake differ from older populations. While IPE demonstrated benefits for body composition, its impact on overall weight management appears limited, warranting further research into age-specific interventions for obesity prevention.”