It’s long been doubted as it takes no account of muscles and definess any well-built athlete, serviceman, or similar person as overweight.
As an example the Times compared Arnold Schwarzenegger and Danny Devito. Both have the same bmi but Arnold has a waist-height ratio of 0.47, Danny’s is 0.71.
A far better predictor is your waist-height ratio. The scientists who carried out the study say GPs should be telling people to keep their waist circumferences to less than half their height.
Researchers at Oxford Brookes University looked at the Health & Lifestyle survey, which goes back to 1984, and the Health Survey for England which studies 8,000 people every year.
Death rates were low for the 10% of people with the lowest waist-height ratios and rose steadily as the ratio increased. People with waists 80% of their height at age 30 lost about 20 years of life.
While bmi shows a similar trend it’s not as strong as using the waist-height ratio.
And for apple-shaped people bmi may give false re-assurance as central fat is more dangerous than fat on the hips. See something I blogged elsewhere: Apples & Pears – What fruit is your bum?