" Functional magnetic resonance imaging studies show that areas of the brain controlling emotion and cognition light up in response to food stimuli. Areas of the prefrontal cortex involved with restraint show decreased activity. In other words, it is harder for people who have lost weight to resist food. 15 This has nothing whatsoever to do with a lack of willpower or any kind of moral failure. It’s a normal hormonal fact of life. We feel hungry, cold, tired and depressed. These are all real, measurable physical effects of calorie restriction. "

― Jason Fung , The Obesity Code: Unlocking the Secrets of Weight Loss