Nikki Blonsky plays a teenage girl trying to become homecoming queen despite the fact that she isn't a "model" figure. She's overweight, has a overprotected mother who while having genuine care for her daughter's health, still comes off as controlling and discriminatory with her approach.
The fat-acceptance movement in America has been looking for something that best expresses the viewpoint of overlooking stereotypes, and I would say that they probably aren't going to find a better outlet or voice in their argument than this movie. Nikki plays a fat girl, but a REAL one, and yes, she DOES have a somewhat eating/snacking problem that has caused a lot of her weight, but she also does have friends who love her, does hold love for herself despite her flaws, and isn't a princess the despite the fact that she's the "underdog." The movie does portray her mistakes she makes with her friends and goes to show that an underdog, fat or not, does make the same mistakes anyone else does and is really no different from anyone else.
It's a cute and warm movie that people as a whole will geniunely like.