Mr. Basile. Diets fail because they are temporary. The only real way to LOSE the weight and keep it off is to change how you eat, period.
I follow a "bodybuilding menu" if you will; I stick to chicken and steak, whole grains, and vegetables and fruit. I eat like this six days a week, and have a "cheat day" once a week to "keep it honest". I've kept the weight off for almost two and a half years now, and feel great. This works for me.
Diets are a good way to "get started", but if someone is going to get absolutely serious about losing weight, they have to change their eating lifestyle. I'm not saying it should mirror mine, but it is a sacrifice they're going to have to make. If they need that much more encouragement to do so, then that's what they should get. If they're going to do nothing more than wallow around in their own self pity, that's on them.