Effect of glucomannan supplementation on body weight in overweight and obese children: protocol of a randomised controlled trial

Introduction Glucomannan (GNN), a water-soluble dietary fibre derived from the plant Amorphophallus konjac , is marketed for weight reduction. The exact mechanisms by which GNN might exert its actions are unclear. However, it has been shown that GNN slows gastric emptying by forming a viscous gel of large volume, which increases the feeling of satiety. Current evidence on the effectiveness of GNN for weight reduction is sparse, and well-designed trials performed in children are needed to assess the efficacy of this modality. We aim to systematically evaluate the efficacy of GNN consumption for the management of children who are overweight or obese. Methods and analysis Children aged 6–17 years who are overweight or obese (based on the WHO growth criteria) will be randomly assigned to receive GNN or placebo (maltodextrin) (both at a dose of 3 g/day) for 3 months and will be followed-up for 3 months. Before the intervention, all children will receive dietetic advice, and they will be encouraged to engage in physical activity. The primary outcome measure will be the body mass index-for-age z-score difference between the groups at the end of the intervention. Ethics and dissemination The study was approved by the Bioethics Committee of the Medical University of Warsaw. The findings of this trial will be submitted to a peer-reviewed journal (paediatric, nutrition or gastroenterology). Abstracts will be submitted to relevant national and international conferences. Trial registration number NCT02280772.