Friday, April 22, 2005

Is being a little bit overweight good for you?

This item from Health Facts and Fears is a perfectly straightforward discussion of the new research from the CDC - although, like the researchers, it assumes that obesity is automatically bad for you and then tries to explain the results that way.

What this discussion misses is another point made by the CDC researchers - that the risk of mortality due to being overweight is rarely more than double, and only at younger ages. As you get older, age rather weight is massively more important as a factor.

The other point is that at least some of the excess mortality may be due to factors associated with obesity rather than the obesity itself. In an environment where food is ubiquitous, people will on average be heavier than before. So, other healthy factors previously associated with a 'normal' or 'overweight' BMI may now be associated with people at the lower end of obesity in the present environment.

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Morbid youth

'Child diabetes timebomb warning', reports BBC News on figures suggesting the number of children with type 2 ('adult-onset') diabetes is on the increase. Figures from two hospital trusts in London suggest there are 22 cases in east London - and 95 per cent of these kids were overweight or obese. Previous research indicated that there might be around 100 cases nationally. Diabetes UK now believes that the figure is likely to be between 1000 and 1500. Concerns have been raised, because 10 years ago type 2 diabetes was unheard of among children in Britain. Diabetes UK chief executive Douglas Smallwood said: 'These cases confirm a shocking trend that type 2 diabetes in children is increasing. Unless children are educated to eat a healthy diet and take up physical activity the number of children with the condition will continue to increase.'

Even with these new estimates, the proportion of children affected is still tiny. The rise in figures may be in part due to one or two cases receiving a lot of attention, resulting in more cases being spotted. In addition, definition of diabetes has changed in recent years, which is likely to have led to an increase in obese patients being defined as diabetic.

Nor is it true, as some reports suggest, that type 2 diabetes is completely novel in children. Paul Ernsberger of Case Western Reserve University tells Paul Campos in his book The Obesity Myth that childhood Type 2 diabetes 'has been known for decades, but no-one ever determined its prevalence until recently. Until recently, epidemiological studies focused on white urban middle-aged men and women, while children, minorities and inner-city residents were ignored'.

However, the most pointed statistic from this latest report is that all but one of the 22 cases were in children from black and minority ethnic (BME) backgrounds. 'Type 2 diabetes tends to develop sooner in people of BME origin and the prevalence is at least five times higher', says the Diabetes UK press release. Dr Jeremy Allgrove, one of the new report's authors, told spiked that: 'We are starting to see it in the white population, it's not exclusively confined to black and Asian populations - but it's more common there, in the same way that type 2 diabetes is more common in the Asian population in adults.' Across the country, however, most of the cases are in BME patients.

As an article in the International Journal of Epidemiology noted in 2002: 'The number of people with diabetes worldwide is set to double in the next 20 years, as a result of increasing obesity and longevity. While some of this increase will be observed in Europe and North America, it is clear that the bulk of the epidemic will be observed in non-European origin populations, in countries undergoing rapid westernisation. If anything, the European origin populations are the anomaly, being substantially protected from type 2 diabetes compared to other world populations.'

So there appears to be a genetic predisposition to type 2 diabetes in certain ethnic groups, in particular those from south Asia. While changes to diet and exercise make sense for those diagnosed with type 2 diabetes, exhorting the wider population to change their lifestyles does not.

The underlying moral message that we need to change our habits is repeated despite the fact that the numbers of children found with this condition are tiny, and obesity is not the most important factor. Starting a debate about a significant health problem in minority communities might have been better - but that doesn't fit the script.

Child diabetes timebomb warning
, BBC News, 19 April 2005

Book review: The Epidemiology of Diabetes Mellitus: An International Perspective, International Journal of Epidemiology, 2002, 31

The changing classification and diagnosis of diabetes, British Medical Journal, 8 August 1998

Obesity sends Type 2 diabetes rates in children soaring, Diabetes UK, 20 April 2005