Abstract
de la Haye, Kayla
PhD Candidate, University of Adelaide and CSIRO Food and Nutritional Sciences
Fat ain't phat. And, it might be contagious
In large social networks, obesity has been found to spread from person to person, as if it were contagious. Both adults and teens are more likely to become overweight if they have overweight friends. Can this be true? Is so, how could we actually 'catch' obesity?
Our research looked at changes in body weight in teenagers and their best friends, over their first two years of high school. The aim of the study was to see if friends had similar body mass indexes (or BMIs – a measure of excess body weight), and if these similarities actually increased so that obesity spread through networks of friends.
Our results showed that friends did have similar BMIs, but that these similarities came about mainly because overweight teens were stigmatised by their peers, and so become friends with each other. Over the two years of the study, there was only weak evidence that friends' BMIs became even more similar. However, we did find that behaviours that are related to obesity, like physical activity and eating habits, were spreading from one friend to another. Young people tended to change their exercise and eating habits so that they became more similar to the habits of their friends.
These findings help to explain why health outcomes, like obesity, might be contagious over the long term. How we harness social networks to spread healthy behaviours and positive health outcomes is the next step.