They get caught on plateaus. In that case what you need to do is give yourself a couple of days of rest and bump up your calories by 10 percent. When you lose weight quickly, your body often responds by releasing hormones to increase your appetite and store more fat. That's a survival instinct meant to help us conserve fuel during times of famine. You can outsmart it by eating a little more and resting. That usually helps jump-start your metabolism again.