Could you speed up your weight loss by eating whatever you want five days a week? Dr. Michael Mosley, the author of The Fast Diet reveals his secret behind the new weight-loss craze that helped him drop from 28 percent body fat down to 20 percent. "Essentially," he explains, "what you do is eat what you normally would five days a week, and for two days a week you cut down to about a quarter of the calories." Watch the video above to hear more about the "Fast Diet" from Dr. Mosley, and check out how one of Rachael's viewers did when she tried it!