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April 19, 2014

Weighing up the obesity campaign

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Dr Muiris Houston

The reasons for rising obesity rates are more complex than they might appear and current health campaigns are stigmatising overweight people, writes Dr Muiris Houston.

Many readers will be familiar with the controversial research that claims obesity spreads like a virus through networks of friends.

It’s the work of Dr Nicholas Christakis, a social scientist at Harvard, and James Fowler, a social scientist at the University of California in San Diego.

The first paper reporting that obesity could spread like a virus was published in 2007 in the New England Journal of Medicine. In it, Dr Christakis and Dr Fowler used data gathered from over 12,000 subjects in the Framingham Heart Study. The data included 32 years of medical records, including details of body weight.

But the Framingham researchers also happened to know who among the subjects were friends; they had asked participants to name a friend who could be used to contact them at the time of future follow-up.

Analysing the Framingham data, Dr Christakis and Dr Fowler found that friends, and friends of friends, had similar levels of obesity, but neighbours did not. The researchers then offered three possible explanations for this: homophily, or a tendency to choose friends like one’s self; an environment shared by friends, so all are affected by the same environmental influences; or contagion, whereby a person’s idea of an acceptable weight changes when he sees how big his friends are.

In choosing contagion as an explanation, the social scientists were essentially saying obesity was a form of infectious disease in which our friends’ propensity for eating large potions of food made us eat similar amounts.

And if this contagion is real, they further argued that people who are fat should stay away from fat people in order to control their weight.

Going viral
There the issue may have rested, perhaps being debated in more obscure academic journals, if it wasn’t for their decision to publish a book called Connections, expounding further on their theories as to why smoking, obesity, happiness and loneliness were essentially ‘infectious’. One of the authors also set up a company called MedNetworks, which offers to help drug companies use social networks to “increase sales force effectiveness and improve sales”.

But the concept then went (excuse the pun) viral and landed close to home when Safefood, the all-island food safety body, came up with a new obesity public health campaign.

“Two in three people on the island of Ireland are carrying excess weight, yet only 38 per cent recognise they have a weight problem. That means a great proportion of the population are in denial, putting themselves at increased risk of well-known diseases such as heart disease, diabetes and some cancers. This campaign issues a wake-up call, asking people to take a hard look at themselves, to find out their own waist measurement, and to ‘stop the spread’,” the literature states.

And the campaign video is even worse. You can catch it on YouTube — complete with apocalyptic music, before the narrator tells us in a doom-laden voice: “We are all in the grip of an epidemic.” It is also claimed that Irish people “are rapidly passing it on to others”.

So, courtesy of the US contagion research, the message from Safefood is clear: the 66 per cent of us with a waist size greater than 32 inches (women) and 37 inches (men) are in denial and are rapidly passing on our weight issues to those around us.

'Thankfully, the original research is now being challenged, although it’s perhaps a little late in terms of shifting the grip the original premise has on the public'

Thankfully, the original research is now being challenged, although it’s perhaps a little late in terms of shifting the grip the original premise has on the public.

Russell Lyons, Professor of Maths at Indiana University, recently published a fairly damning review of the work on contagion of social behaviours, saying: “I know that many professional statisticians felt it was all bunk from the word ‘go’.”

His paper, ‘The Spread of Evidence-Poor Medicine by Flawed Social Network Analysis’, argues the original data is completely inadequate to ascertain the role contagion might play in lifestyle behaviours.

Other statisticians have written that it is mathematically impossible to use observational data to establish that contagion is a major reason why behaviours spread. Conclusions based on observations of how people behave are simply unreliable.

Ignored evidence
Christakis and Fowler have also ignored evidence that for a substantial minority of people, factors other than personal selfishness and laziness can contribute to extra weight.

Many people are now prescribed beta-blocker drugs to prevent them having a heart attack or stroke. But beta-blockers are known to slow down the body’s metabolism and can make it difficult to lose weight. Thousands more take psychoactive drugs, which as a side effect add to a person’s weight.

What about the many Irish people with either undiagnosed or poorly-treated thyroid disease? And do they honestly believe that genetics doesn’t have some role in obesity?

As for Safefood, it is an absolute mystery that someone on the board of the organisation didn’t see the damage that would be done by stigmatising those who are obese.

My understanding is the TV and radio campaign is set to run again soon. It would be a real sign of maturity if the organisation withdrew the obesity campaign in recognition of the dodgy statistics behind many of its public health messages.