Glucomann flour aka Konjac flour
 

Apparently its a fiber taken from the Konjac root. Shiratake noodles are made from it. Its supposed to be good for weight loss as it absorbs liquid and kind of expands in your stomache. Its also supposed to lower bad cholesterol and slow the absorption of blood glucose, so its saying its great for diabetics. Also, you can use it as a thickener as opposed to corn starch or flour, with very few carbs.

Anyone tried it?

I add the powder to my protein shakes (blended with ice) to turn them into a soft serve. Its a great thickener.

As far as weight loss goes, it adds volume, but there is nothing magical about it. If it helps to curb appetite a bit and results in fewer calories consumed, that can help with weight loss.

If, however, you are already following a calorie controlled diet it won't make a difference.