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Tuesday, July 22, 2008

What's the Ideal Weight for a Japanese?

Regular readers of my blog know about my issues with a weight-based definition of obesity. As I have repeatedly pointed out, good health is possible over a wide range of body weights and weight alone is a rather poor measure of overall health.

Not surprisingly the same appears true for the Japanese. At least according to a paper just out in OBESITY, in which Atsushi Hozawa and colleagues from the Shiga University of Medical Science, Otsu, Japan, examined the relationship between BMI and all-cause mortality in 8,924 Japanese men and women without stroke or heart disease.

During 19 years of follow-up, 1,718 deaths were observed. As in other populations, the relationship between BMI and fatal events was U-shaped. Risk of total mortality was highest in participants with BMI <18.5 and lowest in participants with BMI 23.0-24.9. These findings persisted even after excluding the first 5 years of follow-up with a focus on healthy participants. For both the full sample and healthy participants, all-cause mortality risk did not differ between BMI ranges 21.0-22.9 and 23.0-24.9.

These data are particularly of interest because recent recommendation from the WHO and others suggest that a BMI > 23.0 should be considered overweight in Asian populations.

This would obviously make little sense if mortality is in fact lowest in individuals with BMI between 23.0-24.9.

Once again, this study illustrates the problem with BMI-based definitions of obesity which fail to take into account the huge inter-individual variability in the impact that excess body fat can have on health.

While there is no doubt that some Japanese with a BMI as low as 23 may have a full blown "metabolic syndrome", others (perhaps the majority) at the same BMI may be perfectly healthy.

Clearly it is time for a health-based rather than a solely anthropometric classification of obesity.

Edmonton, Alberta

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