I think it was a site called "Intelihealth" associated with Harvard that gave a good summary concerning fasting in general. It's not necessary or beneficial and it is potentially harmful. It doesn't rid the body of toxins or any of this other nonsense that the sellers of false hope claim. Before you trust GNC or any of these other folks with good intentions who are misinformed be aware they carry many snake oil products. Like Enzyte the pill that claimed to increase your erection size, the guy is now facing 30 years in prison.