Near the end of Presto! by Penn Jillette. It's ostensibly about him losing 100 lbs, but it's more like a travelogue of interesting things he did during that time where food comes up, with various food-focused nuggets scattered about. He's vulgar, makes a ridiculously large number of sexual references, and is hugely entertaining in doing so.
It's the first book by him I've ever read, and he's a real character. I could read more by him - but I'd want a break first. His writing is turned up to 11 with anecdotes and such that tend to blur with too many close to each other.
As a diet book, it doesn't budge the needle. As a inspiration to diet, it is likely decent for the type that like him and are willing to try something radical. As a chapter in the life of Penn Jillette - ah, that's what this really is.