Last updated: 2026-07-08

A Body Shape Index (ABSI)

A Body Shape Index (ABSI) describes body shape from three measurements: waist circumference, height, and weight. It was introduced by Nir Krakauer and Jesse Krakauer in 2012 as a way to read abdominal girth in the context of overall body size, and it serves as a screening figure for people interested in body composition and the health risks tied to central fat. Unlike the raw waist, ABSI is built to be statistically independent of height and body mass index, so it isolates the part of abdominal girth that is excessive for a given body size — the part most strongly linked to mortality risk.

What the index represents

A wide waist is partly expected: taller, heavier people tend to have larger waists. ABSI separates that expected portion from the rest. It takes the waist and divides out the contribution of overall body size, captured through body mass index and height. What is left is the abdominal girth that exceeds what the body size would predict. Because the construction makes the index independent of height and BMI, two people of very different size can be compared on the same scale, and the number reflects shape rather than stature. Higher ABSI means more central girth for that body size. Typical adult values sit near eight hundredths.

The formula

Here $\mathrm{WC}$ is the waist circumference in metres, $h$ is height in metres, and $\mathrm{BMI}$ is body mass index in kilograms per square metre. The two-thirds power on BMI and the square root on height are the exponents that make the result statistically independent of those two quantities across a population, which is what lets the index stand for shape alone.

Worked example

Consider an adult with a waist of 85 cm33 in, a height of 175 cm69 in, and a weight of 70 kg154 lb. Body mass index comes first, then ABSI with the waist and height in metres:

A value near eight hundredths sits close to the typical adult range, consistent with a waist that is about what the body size would predict.

Interpreting the number

There are no simple universal cut-offs for ABSI. It is usually read as a z-score against age- and sex-matched population norms: a value near the average carries average risk for that body size, while values well above it have been associated in observational studies with higher mortality risk. Because the index is designed to be independent of height and BMI, it adds information that those measures miss — in the original study it predicted risk even among people with similar body mass index. For an individual, the trend across several measurements usually says more than one reading against population averages.

Limits

ABSI is a statistical construct, not a body-fat measurement. It assumes the population relationships used to derive its exponents apply to the person being measured, and it takes no account of muscle, bone, frame, or the difference between subcutaneous and visceral fat. It is best used alongside other measures such as the Waist-to-Height Ratio Calculator and the BMI Calculator, and any health decision should rest on a professional assessment rather than a single index.