Those aren't scams, but they'll only work for certain types of people. I'd say go ahead and join, but know that they're in business to earn a living, and they'll come up with all kinds of things to sell you. The education you'll get about diet & nutrition is good, and it never hurts to have several opinions. The fundamental rule for losing weight and keeping it off, is to eat what you need; NO more than that. Most people I know of, who go "on a diet", fail. That's because they're starving themselves or they're avoiding food they love, and it drives them crazy after while. Just cut the portions, and keep on eating most of the types of things you eat, but naturally think hard about the fatty things like fries and salad dressings. Those are the deal breakers, even for those who eat basically healthy diets. Most people will gain more body fat by eating a garden salad with bleu cheese dressing than with a cheeseburger!
Charles