One in four UK adults is obese. In 2021 the total cost of overweight and obesity in the UK was estimated at £98 billion1. Presently, emphasis is placed on strategies for obesity treatment rather than proactive prevention. Although strong evidence suggests that preventing weight gain in early adulthood when weight gain is fastest, is critical for reducing obesity risk and preventing chronic disease later in life. High daily fibre intake is inversely associated with body weight. Fibre may exert this effect via enhanced fermentation by bacteria in the colon and the production of short-chain fatty acids (SCFAs), which have been shown to confer a health benefit on the host. However, only 10% of the UK population reaches the recommended intake of 30g of fibre per day and therefore forfeits the beneficial effects of SCFA production. We developed a novel food ingredient, inulin-propionate ester (IPE), to target delivery of the SCFA propionate to the colon, releasing propionate equivalent to the fermentation of 60g of fibre in 10g IPE. Our previous clinical studies in overweight, middle-aged adults demonstrated that IPE prevented weight gain and lowered abdominal adiposity over six months.
This randomised, parallel-group, placebo-controlled, double-blind trial aimed to investigate the effect of increasing colonic propionate concentrations using IPE on preventing weight gain in young adults aged 20 to 40 years old. The secondary objectives were designed to investigate whether the increase in colonic propionate via IPE could beneficially affect body composition and cardiometabolic biomarkers.
We recruited 270 (n=135 per arm) young adults who were overweight and demonstrated behaviours associated with weight gain. Participants were randomised to either 10 g IPE or 10 g inulin control, consumed daily for 12 months.
At 12 months, body weight was 78.9 kg ± 11.8 (n=114) and 81.4 kg ± 11.9 (n=112) for inulin and IPE, respectively, resulting in a non-significant baseline-adjusted mean difference in weight gain of 1.02 (95% CI: -0.37 to 2.41) kg for IPE versus inulin control. Amongst secondary outcomes, the adjusted difference in means for fat-free mass; 1.07 kg (0.21 to 1.93), body water; 0.72 kg (0.1 to 1.33) and fasting glucose; 0.11 mmol/L (0.01 to 0.21), were statistically significant, being higher for IPE compared with the inulin control.
In conclusion, contrary to prior evidence, IPE did not prevent weight gain in this cohort of younger adults at greatest risk of weight gain. These results suggest that younger adults may respond to IPE differently compared with middle-aged participants from previous studies. However, it is noteworthy that the IPE-consuming participants had augmented fat-free mass, suggesting that propionate may have a distinct effect on body composition. Future research should explore differences in the colonic environment, metabolism, and appetite between younger and older adults.