'Thin privilege'

Recently I have seen a whole bunch of tweets and social media posts, about 'thin privilege'.
Posts saying things such as 'thin privilege is being able to go to the doctors with back pain and not being told to lose weight', 'thin privilege is being able to speak to a GP about anxiety and them not suggesting losing weight'.
This makes me angry on so many levels.
Firstly, it is doctors duty to raise public health awareness around weight issues. 
What is there to say that if a thin person went to the GP about something physical that the doctor wouldn't suggest they put on weight?
People presume doctors don't do this, but they do.
I have seen my asthma nurse several times in the past for check ups and she has suggested I put on weight.
I don't think people mean to be cruel when they post things like that on social media, but it is cruel. How can anyone say people who are thin are privileged, when nobody knows how awful their life might be. Nobody knows the battle they might be facing every single day, the battle that revolves around their weight and their image.
I know it can be argued that larger people who receive these comments, from doctors and the like, are being discriminated against for their size. I am by no means someone who thinks 'fat discrimination' is okay, it is not on any level. But the way to combat 'fat discrimination' is not to call thin people privileged.
To state that thin people are privileged to be thin, insinuates that larger people are not privileged.
It's ridiculous, there is no such thing as 'thin privilege', just as there is no such thing as 'overweight privilege'. We are all privileged to be on this earth, no matter what we look like.