Some people derive pleasure from being whipped or electrocuted.
But it's still logical to forbid people from whipping or electrocuting somebody when the consent cannot be determined.
Regardless of whether its done to yourself or to someone else, physical damage/harm's definition remains the same. If someone
likes to harm themselves, they have psychological problems that they should get sorted out.
I've never met anyone who derives pleasure from being electrocuted, and I'm pretty sure if such a person exists, their life is messed up in a lot of other areas too, which again shows a pattern of psychological problems.
1) You are automatically assuming what is physical discomfort and what is not... for some people, dieting or exercising ARE physical discomforts greater than being fat. But you are assuming everyone must agree with your point of view.
Exercise is not a discomfort if you start small and get bigger with time. If someone starts with tiny weights they can easy lift, or starts with slow/fast walking and works his way up to running, it would not be a discomfort. They're simply using a wrong technique if it causes them discomfort. Everyone can start with something in their comfort zone.
2) Even if they were "absolute physical discomfort", if people derived pleasure from it, why should they seek help? What is the purpose? For what moral reason should they be converted to your point of view?
Because it shows clear psychological problems if someone derives pleasure from being kept in the state of a lot of discomfort. In order to help them become productive members of the society they should see a therapist. I've never met a fat person who is happy with his life, overall.
Anyway, this discussion is going in circles now. If someone really wanted to be fat, they wouldn't care about the insults that come with it. If I want to marry a black girl, I will become the laughing stock of my family but that wouldn't stop me from doing it if I wanted to. I have a big nose too. You can make all sorts of jokes about big noses if you want, but that wouldn't cause me to want to get a plastic surgery. If someone genuinely wanted to be fat, they wouldn't be offended by jokes about it.
That's all I gotta say on this.