Calling him names wasn't necessary, but his point remains. You don't eat at McDonalds and drink DrPepper when you want to get thinner. This guy didn't want to get thinner. He didn't want it more than death. And so he died.
But what was making her want to die? Do you think she was unaware of it, or unaware that she was having thoughts that she couldn't seem to control? Could it be the case that living with major depressive disorder might have been so mind-rendingly terrifying that it made even death seem more desirable? But isn't the best solution in this case not really death, but rather for the depression to go away, and only failing that would one ever want to die? Don't you think a suicidal person would be more aware of this than anyone?
You say this guy wanted to get thinner but he also wanted to keep overeating, and unfortunately he didn't seem to want to get thinner enough, so he kept eating. But what he really wanted was for his uncontrollable desire to overeat to go away, and he could not make that happen himself.
It's like telling a paraplegic that he can't get up the stairs because his legs are fucking lame. It's technically true, but it doesn't help in any way.