Articles I've read hint she's got some sort of psychological disorder and a few co addicts in her family who supported this behaviour in the first place. Hope she gets help before she's harmed herself and her family (the kid she's got to look after) seriously. (I know the popular connection between BMI and health often is superficial - but gaining that forcibly and quickly can, for example, do more damage on the liver than years of binge drinking.)

"Hoher Sinn liegt oft im kindischen Spiel." (Friedrich Schiller)