Glucomannan (GNN), a water-soluble dietary fiber derived from the plant Amorphophallus konjac, is marketed for weight reduction. The exact mechanisms by which GNN might exert its actions are unclear. Nonetheless, 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 overweight and obesity in children.

Methods and analysis

Children aged 6 to 17 years with overweight and obesity (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. Prior to 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 BMI-for-age z-score difference between the groups at the end of the intervention.

Inclusion Criteria:

• age 6-17 years;
• overweight or obesity based on the WHO (World Health Organization) growth charts/references (>+1 standard deviation [SD] or >+2 SD, respectively)

Exclusion Criteria:

• drug therapy for a chronic disease (including drugs that influence appetite or body weight);
• type 1 or 2 diabetes;
• history of surgical treatment of obesity;
• participation in another program for treating obesity during the project and/or 3 months prior to recruitment;
• secondary causes of obesity;
• pregnancy.