Glucomannan (Amorphophallus konjac)

Glucomannan is the only weight-loss supplement with an EFSA-approved health claim under Regulation (EU) 432/2012. The approval terms are explicit: 3 g/day (1 g three times daily) with a large glass of water 15–30 minutes before meals, within a calorie-restricted diet. The Onakpoya 2014 meta-analysis reported average weight loss of 0.79 kg over 5 weeks vs placebo – modest but statistically significant. Glucomannan is not a «fat burner» but a tool for portion control and satiety. Without a caloric deficit and physical activity it does not work. Patients with constipation tendency or those whose other medications can be slowed should discuss use with a gastroenterologist or general practitioner.

On iHerb and marketplaces glucomannan is often sold «for constipation» as a natural laxative. EFSA has not approved a separate bowel-function health claim – outside the weight-loss indication this is off-label use. Glucomannan increases stool bulk by retaining water, similar in theory to other soluble fibres, but quality RCTs with stool-frequency endpoints are sparse. In some patients concentrated glucomannan worsens constipation and causes bloating. AGA 2024 and SEPD recommend dietary fibre, adequate fluids and physical activity for chronic constipation, with macrogol, lactulose or prucalopride as needed by physician prescription.