[deliciouscoffee]

There's an interesting study in the New England journal of medicine related to this. The authors found that having social ties to an obese person significantly increased an individuals chance of becoming obese.

From the study: A person's chances of becoming obese increased by 57% (95% confidence interval [CI], 6 to 123) if he or she had a friend who became obese in a given interval.[0]

One of the authors is quoted as saying: “You change your idea of what is an acceptable body type by looking at the people around you,” Dr. Christakis said.[1]

[0]http://www.nejm.org/doi/full/10.1056/NEJMsa066082 [1]http://www.nytimes.com/2007/07/25/health/25cnd-fat.html

[tdfx]

And going out to eat with them probably doesn't help, either.