@Barbarella to be fair, I think a lot of mental illness goes into eating yourself into being a quarter of a ton. Depression at the very least, and maybe unaddressed trauma. Quite a few people on 600lbs life claimed they were raped or molested in their youth. But mostly, yes, I'd say it's a deficiency in character as it is in Whitney's case.
Also, I have never encountered someone with a legit ED like bulimia or anorexia claiming to have felt relief when they were found out. If anything that's stressful because you have this voice in your head telling you it knows what's best for you and these people are going to fuck it up now. They go through great lengths to conceal it.