Shame is a very personal thing, attached to very personal experiences, processed differently, by different people, in different ways.
Culture impacts all of the above.
In MTF culture, we generally feel shame at our 'wrong bodies', though I don't speak for everybody, for sure, and adjusting our weights and body proportions into those more appropriate for our internal self-image is often not only important, but a life-saving process. I lost almost 90 pounds in my transition from a male-bodied person to a female-bodied person. This made my recovery from my surgery much faster, and the surgery itself, much safer. The fact that having a slender body helps me pass as somebody that was not ever male, helps my self-esteem and empowers me to live a fuller, better, happier life.
As for the 'patriarchy', well, I would counter and say that the female form, whether rubenesque, or twiggy-like, reflects current, and ever changing trends, but is nearly always rooted in the biological imperative to reproduce. For those that have no such instinctual 'drive', the pursuit of the currently 'most desirable' female form may seem like pandering to the tastes of the 'patriarchy', when, in fact, it may be nothing more than women competing biologically for the best mates, in an evolutionary fashion, and is therefore a phenomenon driven from below, rather than above. I know that for myself, and many binary-wired females, we would desire to look our best, be at the lowest healthy weight possible, and do anything, and everything to boost our self-image, health, and self-esteem, and we would very likely continue to do so, even if we lived in a matriarchy.
bod·y sham·ing
noun
the action or practice of humiliating someone by making mocking or critical comments about their body shape or size.
adjective
expressing mockery or criticism about a person's body shape or size.
I have never, ever, seen an instance of actual body shaming within the community. I have heard catty remarks, and jealous gossip, and all manner of ugliness, but never have I witnessed actual body shaming.
Sometimes my own shame has colored how I have perceived and received the input of others. But, objectively, nope, never saw actual body shaming...
Missy