" will go along with a diet once or twice—but then it starts fighting back. When fat lab rats are put on a controlled diet for the first time, they’ll lose weight. But if they’re then allowed to eat freely again, they’ll gradually fatten up, and if they’re put on another diet it will take them longer to lose the weight this time. Then, when they once again go off the diet, they’ll regain the weight more quickly than the last time. By the third or fourth time they go through this boom-and-bust cycle, the dieting ceases to work; the extra weight stays on even though they’re consuming fewer calories. "

― Roy F. Baumeister , Willpower: Rediscovering the Greatest Human Strength