Modesty is the most important question. However, in the spirit of the "debate," even though it is badly framed, there is unfortunately a real cultural movement in the 21st century which seeks to glorify and excuse another vice, namely, that of gluttony.
In our society we live in a very difficult situation, because our usual mode of existence presupposes that we actually do very little physical work and movement, compared to our ancestors, in most cases. On the other hand, we have access, in the developed world, to almost endless cheap, easily prepared or preprepared food, most of which is scientifically engineered to taste delicious, and is full of additives which aid even more to make us fat. So I think the so-called "fat shaming" is typically an expression used by feminists and other promoters of vice (gluttony) to stigmatize and condemn the healthy and normal repugnance that exists in any healthy society for those who habitually overindulge, to the point that it affects their appearance and health. The body is the temple of the Holy Ghost, and we do have a duty to look after it, and to keep it up, while tempering our own appetites, for the sake of both good health, and the command of God to fast and do penance.
The sad thing is that as Matthew points out, the discussion today is geared around another vice, of lust, so it's essentially framed as "Which vice means the most to you? Your desire to be sɛҳuąƖly attractive to the whole world? Your desire to show off what sɛҳuąƖ attraction you may or may not have? Or your desire to stuff yourself and make your unappealing figure the standard of beauty, feeding your pride and narcissism?"