Cheerful news for those whose Body Mass Index (BMI) falls into the "overweight" range today - you will probably live longer than a person whose BMI is "ideal". Boffins in Canada and America revealed the new findings following a study of over 11,000 Canadians covering the last 12 years.

Unsurprisingly, people whose BMI showed them to be "underweight" or "extremely obese" died sooner than those in the more middle-of the-road brackets. But the medical community's consensus that anyone with a BMI from 25-30 is "overweight", whereas 18.5-25 is "ideal" has been undermined by the fact that survey subjects in the former, heftier band actually lived longer than the lightweights.

"It's not surprising that extreme underweight and extreme obesity increase the risk of dying, but it is surprising that carrying a little extra weight may give people a longevity advantage," said David Feeny, PhD, one of the study's authors.

Among the individuals tracked during the survey, the most dangerous BMI band to be in was "underweight"; next worst was "extremely obese". Both of these groups had significantly increased risks of dying, 70 and 36 per cent above the norm respectively. Those who were merely "obese" and those with an "ideal" BMI ran very similar risks of death. But the "overweight" were actually 17 per cent less likely than normal to die as time went by.

Good news for the moderately swingbellied swivel chair artist up and down the land, then. If you are "overweight" you're actually somewhat less likely to pop your clogs soon than your fellows, and if you've slipped over the line into "obese" you're seemingly no worse off than the smug "ideal" body types.

These results may not come as a surprise to regular readers of Reg medical and health coverage: we've pointed out the obvious tomfoolishness of the Body Mass Index before now, not least the fact that it requires two-dimensional human bodies to work properly.

Portland State University boffin Mark Kaplan, another study author, cautioned that spindly, unhealthy "ideals" shouldn't bust open the pie locker in a rash attempt to jockey themselves into the safety of an "overweight" BMI, however.

"[This research] doesn't mean that people in the normal weight range should try to put on a few pounds," says the scientist.

That makes sense, as BMI's frequently flawed relationship with real humanity probably has more to do with factors such as the increased height of modern Westerners, the way it doesn't differentiate between muscle mass and lard etc. An "ideal" BMI sufferer putting on a few pounds of muscle by doing some judicious exercise might well stave off death for a bit longer; simply gorging on cakes probably won't help.

Still, at least TV food comic Giles Coren's recent calls for a BMI tax are now further exposed as foolishness, and the "fat people" that he rashly proposes to attack with a stick (any time, Coren - better make it a big stick*) have the consolation of knowing that they'll probably outlive him. ®

*Your correspondent is 6'3" and 16 stone, i.e. "overweight".