Birds of a feather flock together.
A recent study found that your social network of friends influences your weight. In this study, researchers looked at two different schools and tried to see the influence of friends on each others weight. They found that people that are alike tend to be friends, such as those that are overweight or obese tend to be friends with others that are overweight or obese. However, they also found that students that were over weight and had slimmer friends had a 40% chance of losing weight within a year. Also students that were overweight and had obese friends had a 56% of gaining weight during the course of a year and only a 15% chance of losing weight.
So choose your friends well and be a positive influence to your friends for better health.