Friday, August 18, 2006

Fat Heads

Two articles in the new caught my eye. The first one says that the Chinese are now having an obesity crisis with one in five overweight or obese. Note this part on how they figured it.

In China, nationwide, 215 million people out of a total population of 1.3 billion were found to be either overweight or obese in a national survey in 2002, based on definitions given by the World Health Organization.

However, the author of the report, Yangfeng Wu of the Chinese Academy of Medical Sciences in Beijing, thought the figure should be higher because the WHO definitions were designed for Caucasian populations.

According to stricter measurements given by the Working Group on Obesity in China, about 281 million people in China would be regarded as either overweight or obese, he said.

So, on the personal opinion of Yanfeng Wu, nearly 70 million people were re-classified as obese.

But is the BMI of any worth at all? Not according to this article.

Writing in Friday's Lancet medical journal, the researchers from the Mayo Clinic College of Medicine, Rochester, Minn., found that patients with a low BMI had a higher risk of death from heart disease than those with normal BMI.

At the same time overweight patients had better survival rates and fewer heart problems than those with a normal BMI.

This ties in with something I had written a few days ago. At that time I was looking at an article comparing the health of modern people with their ancestors. The finding was that the modern people were much healthier but are overweight according to their BMIs. By contrast, their ancestors who died younger and had chronic illnesses had "normal" BMI.

But, just to show that once a piece of bad science gets out it can never be recalled, the article on BMIs has this paragraph:

About 30,000 people in Britain die due to obesity every year and 300,000 in the United States where the condition is now thought to have overtaken smoking as the main cause of preventable death.
This came from a news release by the CDC a few years ago. It was retracted within days. There were three major flaws in it:
  1. It was actually based on studies of people with poor nutrition and lack of exercise, not obesity.
  2. The death rate was accidentally multiplied by ten. The actual death rate should have been listed as 30,000 for the US instead of 300,000.
  3. It was discovered that higher body mass has health benefits which, when factored in, almost reduce the number of deaths from obesity to zero. Note that this finding has been confirmed by this article.
In fact, since the revised CDC report came out, the emphasis on obesity has changed. Rather than causing increased deaths, it is now stressed that obesity will cause non-lethal health problems such as diabetes.

It should be no surprise that a calculation invented between 1830 and 1850 is a poor indication of health. They were still bleeding people that far back and the idea of washing hands before doing surgery was just taking root. Is seems rather silly to use a 19th century measure to figure ideal body weight.

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