Bob prefers women that are somewhere in the middle, neither fat nor Hollywood Thin.
There are no skinny women in the series, or skinny women are portrayed as unappealing.
The author wants to explore the idea that beauty is in the eye of the beholder or certain fetishes in the work.
Lampshaded: Alice, a slim woman, wants to ask Bob out. But her friend Charlotte points out that ''Every woman Bob ever dated got fat within the month".
Invoked: Bob puts an ad in the personals or uses a dating website specifically to find a Big Beautiful Woman.
Bob thinks an obese woman is unhealthy and unattractive, and only dates unhealthily skinny women.
Bob is embarrassed by his preference. So he tries to get more into skinny women.
Discussed: Danny is talking to Bob about "That episode of Family Guy, where Lois gets fat for Peter". Bob, who claims not to understand the appeal of full-figured women, later falls in love at first sight with the new girl, Alice, and acts like Peter, asking her to gain more weight.
Conversed: Two characters talk about how annoying it is that their neighbourhood seems to have absolutely no full-figured women.