Atletes are used to eat a lot, when they are active they burn off the calories. Then they stop playing but keep the calorie intake. Models and some celebrities are really thin because of oftentimes disordered eating habits and have high pressure to stay thin. After a while the pressure to stay thin disappears or they can't keep up with it so they stop restricting but still have disordered eating so instead of eating moderately they go from one extreme to the other and start overeating.