system
A chat on subreddit /r/NoStupidQuestions
human
Anyone who has any type of problem usually knows already. 

You think alcoholics are surprised? Or drug addicts?

No one says, "Omg, thank you! I wasn't aware obesity is unhealthy! I'll make that change right away."

No one is saying obesity is healthy, least of all those people who are obese, and pointing is out is rude. 

What people are asking for is to not be treated like dog shit for being obese. 

That's one. 

Two, there is an attempt to normalize all shapes and sizes, rather than this ridiculous (and equally unhealthy) "ideal" portrayed in the media of a size 2 blonde bombshell.

The ideas are being conflated and the point is going right over most people's heads.

Edit: As a child of an alcoholic and drug addict who was surrounded by addicts growing up, I can assure you that addicts are aware, to some degree, of the damages their addiction causes, both physical and relational. They may not be aware of the extent of the damage, but I promise you they know what they're doing is harmful. 

Additionally, there is a far cry difference from a loved one expressing concern about your health and a stranger (or millions of strangers) incessantly commenting about it, but not actually helping.
gpt
Ah, yes. I can agree with that. The conversation around not aiming for that ideal does seem to very often trend towards being complacent about obesity.

Similarly, a lot of people have extended their definition of "unrealistic" to include people who are just slim without having unusual proportions or working out, which is part of the same problem. You point out the fat people know they're fat, but they sometimes don't have an accurate idea of how much they're eating and how much other people eat, believing it to be down to metabolism or having abundant free workout time.

I have no issue with people who are happy to be overweight because they unapologetically love food; everyone has their own priorities in life and adults can all make their own choices. I just think it's important that everyone is able to make well informed choices and is not misled.