I'm a librarian who loves anime, manga, and reading a wide variety of genres.
The heroine is Unhappy Fat Person - her fatness is a physical manifestation of her unhappiness. I suppose this could turn around, but right now I'm annoyed at how much the "unhappy --> fat --> unhappy" stuff is being pushed. I'm sure the HEA will come after the heroine has lost weight (thereby signalling that she's happy again). There was a scene in which the heroine had pizza and her bff had a salad with grilled chicken and no dressing, and the heroine's choice was supposed to be a bad thing. Argh.