Actually, just reading the thread title, I am struck by the fact that the word "Fat" is capitalised, whereas the pronoun written in the first person singular ("I") is not.
Yes, we are not meant to draw attention to spelling mistakes, but the difference in emphasis between the two words is very telling, to my mind, at least.
Of course, there are far wider issues here than simply what is perceived to be - or, is all too readily dismissed as - a failure in personal responsibility for one's health.
At no stage is what the OP considered to be "fat" (despite the fact that he was asked to do so on several occasions) defined.
Besides, "fat" is also a social and cultural construct and - and, as Desmond Morris, among others, have reminded us - it is something that is subject to change as fashion - or, economic development - or cultural preferences, change how such things are perceived.
After all, once upon a (distant) time, "Rubenesque" was a compliment, not an insult.
Poor societies and impoverished societies and starving societies don't despise the fat. They envy them.
And, as Susie Orbach has pointed out, it can also be seen as a feminist issue, while Caitlin Moran has argued that food binging is the addiction of choice of carers and the poor and the stressed out, because being able to cope - with shouldering their responsibilities to others - means that whatever they binge on must still leave them capable of coping, which is often not the case with other addictions.
And this leaves out the incessant pressure on women to conform to virtually impossible physical ideals, a pressure that leads many women to have a most unhealthy relationship with both food, - that is food, which is more than simply something to be viewed as an accumulated collection of calories - and with their bodies, let alone other matters such as exercise, or diet.