How this instrument works
A Body Shape Index (ABSI) was built to close a specific gap in body mass index: two people can share the same BMI reading while carrying weight in completely different places, and that arithmetic alone has no way to see the difference. ABSI folds in waist circumference, divided by BMI raised to the two-thirds power and by the square root of height, so a wider waist raises the score even when weight and height stay fixed. The result is a number built specifically to track central fat, the kind concentrated around the abdomen, apart from overall body size.
The index comes from a 2012 paper by Krakauer and Krakauer in PLOS ONE, built from NHANES data collected between 1999 and 2004 on 14,105 American adults. Following those adults forward, the authors found that ABSI predicted mortality hazard on its own, even after accounting for BMI — a waist shaped like a bigger central store carried risk that BMI alone did not capture. That independence, not the raw figure, is the finding the index rests on.
ABSI has not earned the clinical footing BMI has after a century of use; it remains a research-derived measure, most useful read against age- and sex-specific population averages rather than treated as a number with its own universal cutoffs. Treat a single ABSI reading as one data point to weigh alongside waist size, body mass index, and a clinician's own assessment, not as a stand-alone verdict on health risk.
- Enter Waist circumference (wc), measured snugly at navel level, in centimetres or inches.
- Enter Weight (w) in kilograms, pounds, or stone; it feeds the BMI term inside the formula.
- Enter Height (h) in centimetres, metres, inches, or feet — the equation converts internally to metres.
- Read ABSI: the working block shows the BMI term, the height term, and the final division by waist.
Worked example — 70 kg, 1.75 m, three waists
Start with a 70 kg adult standing 1.75 m tall and an 85 cm (0.85 m) waist. BMI works out to 70 ÷ 1.75² = 22.86. Raising that ratio to the two-thirds power gives about 8.05, and multiplying by the square root of height (1.75^0.5 ≈ 1.323) gives a denominator of about 10.65. Divide the 0.85 m waist by 10.65 and ABSI lands at about 0.0798 — the reference value for this exact body.
Keep the same 70 kg and 1.75 m and widen the waist to 1.0 m: BMI and the whole denominator stay at 22.86 and about 10.65, since neither weight nor height moved, so ABSI rises to about 0.0939 — purely a waist effect. Narrow the waist instead to 0.70 m and the score falls to about 0.0657. Same underlying ratio throughout; three different waists produce three different figures, which is the entire reason the index sits alongside body mass index rather than instead of it.
Questions
What does an ABSI score like 0.08 actually mean?
On its own, not a great deal — ABSI is built to be compared against age- and sex-specific population averages rather than read as an absolute figure the way a BMI of 25 or 30 is. A given ABSI value is typically expressed as a z-score or percentile against people of the same age and sex before it says anything about relative risk.
Why does ABSI change when BMI doesn't?
Because ABSI is designed to isolate the waist term from body mass. Two people can share a BMI of 22.86 at 70 kg and 1.75 m, but if one carries an 85 cm waist and the other a 100 cm waist, only ABSI moves — from about 0.0798 to about 0.0939 — because BMI has no way to see where on the body that weight sits.
Is ABSI more accurate than BMI?
It answers a different question rather than a strictly more accurate one. The original 2012 study found ABSI predicted mortality hazard independently of BMI in a NHANES sample of over 14,000 adults, meaning it adds information the older measure misses about central fat — but it has not accumulated anywhere near BMI's decades of clinical use, and most guidance still leans on that older measure and waist circumference directly.
Where do the numbers behind this formula come from?
From Krakauer NY and Krakauer JC, 'A New Body Shape Index Predicts Mortality Hazard Independently of Body Mass Index,' published in PLOS ONE in 2012. The authors derived and tested ABSI on 14,105 adults from the NHANES 1999-2004 dataset, following their mortality outcomes forward afterward.
Should I use my ABSI result to diagnose a health problem?
No — treat it as one screening data point, not a diagnosis. ABSI is a research-derived index without the standardized clinical cutoffs that BMI or waist circumference carry, so a raised figure is a reason to look at waist size, body mass index, and overall context together, ideally with a clinician, rather than a verdict on its own.
Does a low ABSI guarantee low health risk?
No single figure can guarantee that. ABSI captures one dimension — central fat relative to BMI and height — and says nothing directly about blood pressure, cholesterol, family history, or activity level. A low reading here is a reassuring data point, not a substitute for a broader health picture.
References
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.