A new study found that obese friends can also make you fatter. According to this study thin people who socialise with the obese can put on weight. But, here is the good news. The process can work in reverse too theoretically , says the study. The researchers Nicholas Christakis and James Fowler, examined 32 years of data collected during a research of people's hearts in Framingham in Massachusetts . They discovered that where two people who are friends for a long time, and where one is heavier than the other, the thinner friend tended to increase in weight by up to 57% over time.