The Fast Diet, the British diet book that encourages you to down your calorie count intake to 500 twice a week (600 for men), is a conversation that's taking over the web. That's exactly why we opened it up for discussion on InStyle's Facebook page, where we asked our more than 580,000 followers if they would consider the slim-fast plan for themselves. Answers: Desiree Duskin of Huntington Beach, California said: "That doesn't sound healthy." Meanwhile, Mary Gentile Wollmann of Parma, Ohio offered her own must-have slim-down trick: "The only way to lose weight is watch your calories and exercise. Simple." Do you agree? Join the discussion on our Facebook page!