You know..... from all of the bad experiences you've had, you seem to attribute it to being overweight. With the test? You did excellent, and people were resentful. That doesn't have to do with you being overweight - it has to do with you being smart! Not that that's any better, but it's actually a logical connection.

So, people dislike you due to your successes and your intelligence - not because you're large. What have people actually said to you, your classmates, that makes it 100% clear that it's about your weight? Tons of people are jealous of success and intelligence - intelligence isn't something that everyone can achieve (what a shame though!). Body size isn't always a role in that - jealous of intelligence/success are totally their own things! They don't even need to go together themselves - there are tons of successful people who aren't actually very intelligent! And tons of intelligent people who aren't very successful.

The mirror theory goes both ways.... some people make bad first impressions (I think you might be in that category yourself right?)... and if you retaliate, well, those people who make bad first impressions (or whom you misread, because yes, that DOES happen... frequently, to all of us) will then go "why bother!" and just let it be the way you see it. It sucks having to be the better person, but sometimes those people are actually quite great. Just the same as the opposite works - sometimes the people who seem like they're going to be amazing and great friends end up being terrible.

If everyone quits and retalitates then well.... yeah just not very pleasant.

I hope that the person you're going to lunch with is one of those people who doesn't just quit. It'd be great if you could see someone like that!