Smoking cigarettes is a habit loop consisting of stress (cue), nicotine stimulation (routine), leading to temporary psychic well-being (reward). People often gain weight when they try to quit smoking because they substitute food for nicotine as their routine. In doing so, they are obeying Duhigg’s Golden Rule of Habit Change—keep the cue and reward, change the routine—but they are doing it poorly. Doing thirty push-ups (or anything physically challenging) might be more effective than eating more.
