I would say as many as there are inventive people. Really, there is no way to tell, but you can group all those into a few catagories, which is exactly what I did on the home page of this site.
Go to our main page about the Real Easy Weight Loss Program and you'll see where I go into amost all the types of weight loss programs out there.
If you're really interested in losing weight as fast as possible while keeping it off, I explain why and how my weight loss program works in my new weight loss and diet program.