Glucomannan is a soluble fiber from konjac root. In water it swells into a thick gel. That gel can help you feel full and keep your digestion moving.
Most people use it to increase satiety during a weight loss effort, to blunt blood sugar spikes by slowing carb uptake, or to maintain cholesterol numbers already in a healthy range. You can take it as capsules or stir the powder into a full glass of water.
Swallow every dose with at least 8 ounces of water, and do it right before or with a meal to get the fullness benefit. Take medications and other supplements at least one hour apart, since the fiber gel can delay absorption.
Always mix the powder completely and drink it immediately. If it thickens before swallowing, it can block your throat. Glucomannan can lower blood sugar, so check your levels carefully if you use diabetes medication.