No matter what size you are, if you wear clothes that are too small for your body, you are going to be squeezed in places, creating those telltale lumps where you really don’t want them. I don’t think this is about weight. I think we’ve all seen women who are not overweight at all wearing clothing which is way too tight, and it is no less unflattering on them than on someone who is overweight.
That said, I thought this letter was surely a joke and someone was just pulling our legs.