Our expert says:
I don't think this has anything to do with your being fat, if indeed you are fat to any significant extent --- you're describing untalented parents, lacking in the skills to be properly loving towards you ( their fault, not yours ). They probably prefer your sister simply because she is younger and more subservient to them at this stage, but she'll probably run into exactly the same troubles when she starts wanting to be more independent, as she will.
Why not explore the possibilities, at your age, of moving out, to share a flat with some other girls, or whatever works. For your father to try and "ground a 21 year-old" is absurd, but it reveals how much he wants to keep you a child, and has no idea of what to do with you as a woman.
When you can live elsewhere, work independently, and make your own decisions, continue to be a "good girl" for your own sake, not his, and enjoy life as the adult you ought to be.
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