Increase in colonic PRopionate as a method of prEVENTing weight gain in adults aged 20–40 years (iPREVENT): A multi-centre, double-blind, randomised, parallel-group study to investigate the efficacy of inulin-propionate ester versus inulin (control) in the prevention of weight gain over 12 months

Introduction: Overweight and obesity affects over 70% of the UK population and is a major risk factor for the development of co-morbidities, including type 2 diabetes and cardiovascular disease. There now exists a considerable evidence base for the management of obesity. However, this is not the case for the prevention of obesity. Preventing weight gain in periods of life where there is an elevated risk of fat mass expansion could be beneficial to preventing associated diseases in later life. This protocol investigates the impact of novel food ingredient inulin propionate ester (IPE) in the prevention of weight gain. This trial aims to investigate the primary hypothesis that IPE has a superior effect on preventing body weight gain, compared with inulin, in young (<40 years old) adults over 12 months, whilst also investigating several complementary mechanisms that may explain the prevention of weight gain and improved long-term energy balance from consuming IPE. Methods: In this multi-centre, double-blind, randomised, parallel-group study, eligible participants will be randomly assigned to consume 10g IPE or 10g inulin (control) daily for 12 months. Study visits will be conducted at baseline, two-month, six-month and 12-month time points. The primary outcome is weight gain from baseline to 12 months. Secondary outcomes will examine changes in metabolic and cardiovascular health biomarkers, body composition and appetite. A mechanistic sub-group will explore causal mechanisms around energy balance, body composition, appetite regulation and the gut microbiota. Based on the power calculation, the sample size required is 270 participants or 135 per study group. Ethics and dissemination: The trial protocol and participant-facing documents have been reviewed and approved, by the London Hampstead Ethics Committee (REC Reference 19/LO/0095, 29th January 2019). Upon completion, the trial results will be published in peer-reviewed journals and presented at scientific conferences. Trial registration number: ISRCTN16299902, 1st March 2018.