They call it the ‘obesity paradox’ – the notion that those with a higher BMI seem to live longer.
But even this nickname doesn’t really get to grips with what the evidence is saying.
In the news this week is a book called Doctoring Data: How to Sort Out Medical Advice from Medical Nonsense by Dr Michael Kendrick. Some may dismiss it as polemic but Kendirck has some interesting things to say about how scientific data is used and abused by all sides of the health debate.
One of the drums he bangs is the notion that being overweight is de facto unhealthy. Does the data really support this belief? Apparently not.
There is no doubt that obesity can reduce your life expectancy but several important studies have shown that those with a body mass index, or BMI of 25-30 (classified as ‘overweight) seem to outlive the rest of us.
“Normal” weight is often codified as a BMI of between 19-25 and those whose BMI falls below this have long been known to be at higher risk of premature death. Likewise we have assumed that those on the other side of ‘normal’ must be similarly at risk.
And yet, in a 2005 study in the Journal of the American Medical Association, which looked at excess deaths associated with being underweight, overweight and obese, concluded that being overweight was not associated with excess mortality.
This study isn’t a one off. In 2006 in the Lancet researchers looked at data for a quarter of a million people from 40 different studies. They found that the lowest risk of all types of mortality, as well as heart related mortality, was in those people considered overweight. In this group the risk of death was 12% lower than those people considered normal weight.
In this study as in the many others was not until people had a BMI of over 35 (classified as obese) that there was a clear increased risk of premature death linked to weight.
In 2009, a German group looked at more than 40 different studies into weight and premature death as it relates to overweight and obesity. There was no consistent relationship between weight and disease and the risk of premature death was no higher for people who are ‘overweight’ than it was for those of a ‘normal’ weight. Which begs the question do we need to look again at how we classify ‘normal’?
Even accepting that BMI is a sometimes wildly imperfect measure of body size and health – one that ignores gender, age, and muscle mass – you have to wonder what’s up with this data and why, in the face of it, are we still pumping out the – if you’ll forgive me – one size fits all messages about health?
Over the last year or so we have undergone a revolution in a lot of our thinking about things that are ‘good’ and ‘bad’ for our health. Fake sugars – which are supposed to be helpful in controlling weight – have been shown to do no such thing, and what is more are associated with weight gain and a whole host of other ill effects.
Fats which for so many years were blamed for the rise in heart disease have been conclusively shown to do no such thing. What is more, it is clear that data has been present for many years showing that this is the case.
So why does it take so long to reach more sensible conclusions about health?
Look no further than the voracious marketplace. The more we can medicalise some part of the human experience the more we create a thriving market for ‘cures’ – from novel supplements to heavy duty pharmaceuticals – and one in which health experts with varying degrees of expertise can flourish.
We can ignore social and environment influences on health and place the blame for our burgeoning health problems on some sort of epidemic of public laziness or ignorance.
Obesity is a health risk and the data on being overweight isn’t a free pass to eat yourself into oblivion. But it does give pause to think about what health is, and whether fitness isn’t perhaps more important than thinness. Given all the things that can contribute to overweight and obesity – including obesogenic chemicals, stress, lack of sleep, lifestyles that are less active and food sources that are becoming more and more calorie dense and nutrition poor – maybe we should occasionally congratulate ourselves that we aren’t even more unhealthy than we are.
Pat Thomas, Editor
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