Funny but the movie is shallow itself as it's got the idea that beautiful people are shallow inside and ugly people are beautiful. Unfortunately it's not like that in real life. It's also got the bad idea that if you are ugly you should only date ugly people.
Plus Rosemary isn't fat. She's OBESE. This movie promotes the idea of not caring for your health and just eating whatever you want.
Funny and with an (for comedies) exceptionally good plot: Hal only sees the exterior of women until he meets self-help guru Tony. After this meetings Hal can only see the inner beauty of people and he falls in love with the 300 pound heavy Rosemary.