If you look on their website, it looks to me like basically it's metamucil in a pill form. Basically inulin or some other type of fiber that when taken with water turns into a gel in your stomach to make you feel full. Fiber also would impact your cholesterol and blood sugar in the way that PGX says it's product does. So for what it's worth, it just looks like overpriced metamucil.
I've tried the metamucil thing- it gave me horrible heartburn. If you're a volume type eater that needs to feel full, it might help. But in my opinion there really aren't any shortcuts. And unlike what PGX says, diets DO work if you treat them as a lifestyle change and not as a temporary fix. It's looking for temporary fixes to a permanent problem that gets us into trouble, I think. You need to select a permanent solution, which is going to be some version of a healthy diet in healthy portions, and some version of exercise.
"A mistake is not failure but feedback. -Rod Gilbert"