We live in a Society where body shaming is rampant, people feel insecure to be thick and juicy in their body structure, simply because they will be labelled fat
I don't see the problem in telling people, that they are not living healthy, especially if they start complaining about it. Being overweight/obese is one of the main health issues today, which accumulates in billions of medical costs. Besides that, fat people receive sometimes even unfair advantages:
Why do I have to pay extra for my 20 kg luggage on a plane, which will, if added to my body weight, equal roughly 100 kg in total, while a fat person with a body weight of 150 kg pays less, if he has no luggage at all?
My point is:
I don't care about body types, but as soon as somebody complains about how unfair "society" treats him, I will always point out the flaws in his own logic. It's not always the fault of big, bad, evil society, but quite often your own laziness and unwillingness to change.
I think you can shame people for their decisions. Obesity that is the result of a condition is far rarer than obesity that is the result of a choice.