What are my chances of becoming obese?

I found all of the reading to be very interesting and thought provoking, as I have never thought about social networks in this way. I had heard of the six degrees of separation and a small world theories, but had never thought about how connected we all really are. Even the fact that after hours of research, someone happened to find a Russian supporting cast that were all 8 degrees away from Kevin Bacon absolutely surprised me. One concept that I am having a hard time grasping is the Three degrees of influence theory. Lets say I am closely connected with 20 people, and those people all know 20 people who all know 20 more people. That means that there are 8000 people who are all three degrees from me. How do these people have any influence on my life? One example that hung me up was the obesity graph in the TED talk. I think I remember hearing that if someone three degrees from me is obese, I am 10% more likely to be obese. What if there is one obese person, and 7999 skinny people three degrees from me? Am I still 10% more likely to be obese? How about if all 8000 people are obese? I believe that that percentage would go way above 10%. In addition, I believe Christakis also said that if you have an obese person one degree away from you, you are about 50% more likely to be obese. What if I have one friend, and that friend is obese. I would think that my chances would be fairly high that I am obese as well. Now lets say I have 100 friends, and one is obese. Can I use backwards logic to say that I am much more likely to be skinny or fit, or am I still 50% more likely than someone with no obese friends to be obese. I am very interested in these connections, and I would like to look further into these numbers.