but someone who eats buckets fo fried food and icecream and is overweight is never called "fat", "lardarse" or "unhealthy" even though they are.

Yes we are.

I've had total strangers come up to me in shopping centres and tell me off for what I was eating. Never mind it may have been the first chocolate bar I'd had in 3 weeks. I am fat and therefore am a Bad Person for eating it.