Its not new and fiber being used to make you feel fuller has been used for decades. Psyllium husk fiber (the same thing used in Metamucil) was all the rage 10-15 years ago, Glucomannon has shown up in a lot of products lately and the next thing you know, they'll be another fiber supplement.
You can't out-exercise poor eating habits.
Glucomannan absorbs a LOT more liquid than other fibers, so it's considered the best fiber (makes you feel fuller = less hungry). It also doesn't have the side effects like bloating that the wheat-based products like Metamucil have because it's made from a different plant source. Actually, I just might try it and see if it helps.
Not that it matters to me, but Dr. Oz highly recommends it and talks about it often.