Right the problem is that most people who are dieting either do some poorly thought out fad diet or just starve themselves and have minimal knowledge of excercise or nutrition. As a result they lose a great deal of muscle mass with their fat, thus slowing thier metabolism down, and often times when they go back to thier old lifestyle they bounce back to the same weight with less muscle thus end up with a higher bodyfat % than they started with. That is the reality of dieting for the average dieter.