“Starvation mode” is the theory that when you cut calories too low, your body thinks that it’s starving and responds by hanging onto any calories it gets instead of burning them. The result: You gain pounds, rather than lose 'em. But is this line of thinking legit—or just a way to keep people from taking drastic measures to lose weight?
Turns out it's a real thing, says Holly F. Lofton, M.D., director of the medical weight management program at the NYU Langone Medical Center.