Overview

BMI has been used as a measure of health for quite some time, but the data doesn't support a strong correlation between BMI and mortality. The problem is that BMI doesn't distinguish between fat and muscle, or between good and bad distribution of fat.

Recently, waist circumference has been proposed as a more-accurate metric, but this measurement also has it's limitations. Since WC and BMI are highly correlated, so there may be a limit to how much extra information can be derived from WC.

A recent paper suggests a new measure, designed to be maximally correlated with mortality, and minimally correlated with BMI and WC. This may or may not be meaningful. But here's a calculator for it :) Your z-score is based on the data in the paper, and is the number of standard deviations away from the mean for your sex and age you are. Higher is worse.

I'm not sure why this paper ignores WC/Height ratio, which has also been proposed as a metric, and resolves some of the problems given for WC.

Citations for all of the above and a much better discussion of the research is available in this Obesity Panacea blog post by Travis Saunders

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