Actually YES !
Researchers at Harvard Medical School studied 12,000 people over a 32 year period and found that social connections impact your chance of gaining weight.
If your spouse becomes obese, you have a 37% chance of also becoming obese. If your brother becomes obese, you have a 40% increased risk.
Friendships are even more influential. The risk of friends becoming obese together is anywhere from 57- 71 % depending on if the friendship is mutual. This was even true when friends lived far apart.
The idea here is that once someone becomes obese, there is a social acceptability for people who know that person to also gain weight. Attitudes towards obesity change to one of more acceptance of a larger size.
On the positive side, if someone you know loses weight, it will influence you to get thinner as well. So perhaps our social networks could be used to influence us to lose weight if we need to drop a few extra pounds.