Concern trolls are just the wishful thinking 'obesity' police
Fat people are defined by the false hegemony of the 'obesity' construct. That seeks to define fatness as a singular "disease" that has predictable symptoms and a defined course.
This wishful thinking creates an overweening desire to enforce "dis" or unease in fat people, to make 'obesity' seem to be as real as they can make it. Real disease doesn't require such policing. No one insists someone with real disease, must have such and such symptoms.
If they don't then it becomes a feature of that condition, that no everyone has it in the same way.
Notice, fat people are allowed to vary less than people with real disease. The interest in trolling is the urge to make you feel think and act out being sick-whether you are or not- as you have been already assigned by the scientific and medical hierarchy. Folks are able not to care about the damage this may do to you, because you're already defined in their minds as 'damaged goods'.