@Derrick: For many people, it's not an issue of willpower, but of training — many people (myself included) simply have trouble finding the line between "hungry" and "not hungry", so they eat until they're full. Thus, one needs to train oneself on what a healthy portion is, and learn to trust their eyes — and, when all else fails, kitchen scales — instead of their gut.

Now, when you first start dieting, then willpower is a biggie. You're essentially dropping your food intake by a significant degree, and you are going to feel hungry (at least until you get used to it).

I'll agree, though, that these glasses are snake oil. Nice looking, but likely won't make a bit of difference in what or how much you eat. It's amazing how much useless (and sometimes dangerous — i.e. diet pills) crap exists to take advantage of fat people...