Do they sell kon'nyaku (also written konnyaku or konjac) in the U.S.? It is
a very common food here in Japan, and has almost no calories or carbs. You
can read more about it at:

http://www.konnyaku.com/e_data/index.html

At the supermarket you can get dozens of different varieties, shapes, colors
and some with subtle seasonings. It is basically tasteless, but filling.
Some people think it somewhat takes on the taste of whatever it is cooked
with.

If you are low-carbing and/or low-calorie dieting you can imagine it is
somewhat like eating pasta, or even potatoes, when you mix it in with other
stuff. It even comes in pasta-like cuts (shirataki).

I've never tried the powdered version before, but if I do I'll report back.

doug