This is a strange thing to say. If you do something normal, and you end up in a normal state, why would that be a moral failing? There's no such thing as "overeating". Different people eat different amounts. The same person eats different amounts at different times.

> (From that perspective:)a miracle cure that allows someone to stop being fat is like an indulgence (in the Roman Catholic sense). It’s a cheat, a shortcut that allows the unworthy to reach a state they do not deserve.

This is incoherent. If you believe that being fat is a sin, but that the things you do that make you fat are not sins, then a miracle cure that makes you think removes the only sin you were committing. You can't be unworthy if you're not fat. In order for a miracle cure to be "cheating", it is necessary that the sin is in the behavior and not the result.