Connected, the book

I heard of the book on the radio. The hook was that, as they put it, obesity is catching, as are smoking and sexual activity, triggered by social networks with friends of friends being very important in determining behavior.
In my work as a ballroom dance teacher, social networks are very important, so I read the book hoping for more clues.
The findings of genetic predispositions to being in a central position in a social network was not helpful. Both my parents are happiest on the periphery.
Chapters on God and medicine weren't what I wanted either. The book read like an undergraduate text.