I would definitely not say that fasting is more effective than eating right and exercising. Yes you can lose a lot of weight in a short time period but remember in the case of 15lbs in 6 days, a majority of that weight is water weight and not fat lose. Also, by fasting (especially longer fasts) you are slowing down your metabolism because your body does go into starvation mode. Most importantly after fasting you have to keep that weight off by eating again. Fasting can't teach you how to eat right and exercise which are lifelong ways of maintaining weight. It can give you a jump start...or be a quick alternative for an upcoming vacation!