Are your friends making you fat?

How can someone you’ll never know make you fatter, happier and sexier?

The Observer, January 2010

A couple of months ago, about 80 people – some of whom knew each other and some of whom did not – gathered in a small lecture room at Nuffield College, Oxford, to hear a man give a lecture about how, if one of them suddenly got fat, the chances are that others would get fat, too. The same applied to happiness: if someone in the room spent the next week elated, that joy would probably become infectious. And the same for smoking: if a man in the room finally managed to quit, the chances were good that his friend sitting two rows in front of him would quit as well. And then, a short while later, a friend of his friend whom he didn’t know would do the same thing.

The lecture was given by Dr Nicholas Christakis, a professor from Harvard who had flown over to expand on theories that he once thought of as “cockamamie”. His talk examined the power of social networks to influence our behaviour, and suggested that our actions were only partly determined by our own free will. Increasingly, something he called “social contagion” seemed to be getting the upper hand.

Some of Dr Christakis’s theories seemed obvious – the chances of becoming obese because we hang around with obese friends who like eating cake – but some are more surprising, including his findings that we may become obese just by knowing someone who knows someone who is fat.

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