Glucomannan

Amorphophallus konjac fibre

A viscous soluble fibre. It does what fibre does — fullness, slightly better lipids — and the weight-loss numbers are real but small.

What the evidence supports

Moderate Satiety Reliably increases self-reported fullness when taken with water before meals.

Moderate LDL cholesterol Pooled reductions of roughly 10% at 3 g/day, consistent with other viscous fibres.

Limited Body weight Meta-analyses land between 0.8 kg and no effect over 8 weeks. Real, but not what the packaging suggests.

Limited Blood glucose Modest postprandial blunting; long-term HbA1c data is thin.

Dose used in trials

1 g

three times a day with at least 250 ml of water, taken an hour before meals.

Safety

Choking risk if dry

Must be taken with ample fluid — tablets have caused oesophageal obstruction. Bloating and flatulence are common early.

Ask a doctor first if

Three cases

Swallowing difficulty, prior GI obstruction, or any oral medication taken within two hours.

Open any one for sample size, funding and what it actually measured.

Keithley et al. · meta-analysis · weight

Pooled across 14 trials, the effect on body weight was small and not statistically robust once the highest-risk-of-bias studies were excluded.

Sood et al. · 531 adults · lipids

Pooled analysis showing LDL and total cholesterol reductions at 3 g/day, with little change in HDL or triglycerides.

Walsh et al. · 20 women · satiety

Eight weeks. Fullness ratings rose and weight fell modestly, but the trial was tiny, unblinded on diet, and the effect faded after week six.