Over the last thirty years the average body mass index has increased. Not everyone is putting on weight and there are interesting patterns.

A Five Minute Read

Who puts on weight is not random. There is a pattern. It is a pattern of friendship. Obesity is contagious like loneliness. The social networks show it.

If you read last weeks newsletter you will know that Framingham is a special town. Over three generations have taken part in a heart study. They have also listed their family, friend and work connections after every test. This has enabled researcher to build social networks of most of the people in the town. Those networks have been tracked over time. Since Body Mass Index was measured as part of the study they can track where obesity starts and how it spreads. If you want to see the spread, please go to the article and play the video. It shows 32 years of evolution.

The video shows that obesity is very contagious. It too works with up to three degrees of freedom. An obese friend increases you chance of becoming obese by 45%. If your friend’s friend is obese you chances are still 20%. If your friend’s, friends’ friend is obese your chance increases by 10%. There is a strong sex effect. A man who has a close male friend who becomes obese has a 71% chance of following them. A female friend has virtually no impact. A wife who becomes obese only increases their husband’s chance by 45%. We choose a role model from within our same sex friends. Neighbours have less of an effect. Social distance is very important. Your closest friend has the biggest impact. In this case no matter how far away you live.

Using Social Networks for good.

The average person spends about 80% of their waking hours in the company of others. When we are asked, we always prefer time spent with others over time alone. We define ourselves through the people we know and interact with. Despite this when studying things like loneliness, obesity or smoking, policy makers tend to focus on the individual not the context. There is a huge opportunity to use networks for good.

It is not surprising that other researchers have used this unique sample. They have looked at the spread of other emotions. Humans are mimics and sensitive to language and facial expressions. It is not surprising that emotions can spread. One team looked at the spread of happiness. There were within the Heart Study questions about feeling happy.

The results are the same as loneliness. Happiness is concentrated within the heart of the network. In places where lots of people are interconnected. Just like loneliness, happiness spreads. It too has three degrees of separation. You can catch happiness from a friend. You can also catch it from your friends’, friends’, friend. It turns out that the number of happy friends you have can outweigh the number of unhappy ones. Your friends have more influence than your family on your happiness. Closer friends physically and socially have a bigger impact. A socially close, happy friend can increase your chance of being happy by 67%.

The biggest difference to loneliness is that there is no sex affect. Men and women are equally susceptible to the happiness bug. Women were more susceptible to loneliness. The suggestion is that loneliness has a stigma attached to it particularly for men. This may have biased the responses. Happiness spreads more by sex. Like obesity, men influence the happiness of other men more than they do women. The story is the same for women. Does happiness spread more than loneliness? The results are ambiguous. Happiness certainly spreads more than unhappiness. This could be that we are exposed to more happiness. However, loneliness seems to spread more than “un-loneliness”. We do not think about not being lonely.

Network phenomena can be used to spread health benefits. Smoking in Framingham declined like everywhere else in the USA. It this case the decline was contagious in a different way. People did not stop smoking randomly. It did spread through the network. Clusters would stop smoking together between one measurement and the next. The researchers suggest that the social norm changed. Smoking is a social habit as is visible at the back doors of many office buildings even today.

Public health programs seem to work. Their power could be increased by focusing on the social networks. In other spheres key network members have been identified. They are connected to many people. They may provide the only link between two diverse groupings. They can have a disproportion impact on change for good or bad.

Choose your friends carefully.

A network of friends is an important asset. Having lots of happy friends will make you happier. Surrounding yourself with lonely people will have only one outcome. It pays to have younger friends who will not leave you alone by dying. Stay away from smokers and friends who are putting on weight!