Losing weight is not the hard part; it’s keeping it off. New research explains why maintaining weight loss is so difficult – people who have lost weight feel hungrier and have a stronger desire to eat for at least a year after weight loss. The body responds to weight loss by burning fuel more efficiently, making calorie-burning movements more economical, and increasing the impulse to find and eat food. This adaptation evolved to avoid famine, but in societies with abundant food, it hinders dieters. Even with help, very obese subjects still experienced increased hunger and desires to eat long-term. Coping strategies are crucial to sustain weight loss.
https://www.latimes.com/science/sciencenow/la-sci-sn-weight-loss-hunger-20180202-story.html