This year, we Americans will spend billions of dollars on products that do nothing for us - or may even harm us. And we'll do it for the same reason people have done it since ancient times... We want to believe in miracles. We want to find simple solutions and shortcuts to better health. It's hard to resist. All of us, at one time or another, have seen or heard about a product - a new and exotic pill, a device, or potion - that can easily solve our most vexing problem. With this product, we're told, we can eat all we want and still lose weight. We can grow taller or have bigger breasts.…