Body Shape Index

A body shape index (ABSI) is a metric for assessing the health implications of a given human body height, mass and waist circumference (WC). The inclusion of WC is believed to make the BSI a better indicator of risk of mortality from excess weight than the standard body mass index.[1][2] ABSI correlates only slightly with height, weight and BMI, indicating that it is independent of other anthropometric variables in predicting mortality.

A criticism of BMI is that it does not distinguish between muscle and fat mass and so may be elevated in people with increased BMI due to muscle development rather than fat accumulation from overeating.[3] A higher muscle mass may actually reduce the risk of premature death.[4] A high ABSI appears to correspond to a higher proportion of central obesity, or abdominal fat.

In a sample of Americans in the National Health and Nutrition Examination Survey, death rates in some subjects were high for both high and low BMI and WC, a familiar conundrum associated with BMI.[5] In contrast, death rates increased  proportionally with increased values of ABSI. The linear relationship was unaffected by adjustments for other risk factors including smoking, diabetes, elevated blood pressure and serum cholesterol.

The equation for the ABSI is based on statistical shape analysis and is derived from an allometric regression (with waist and height in meters and weight in kg):[6] ${\displaystyle ABSI={WC \over {BMI^{2 \over 3}\times Height^{1 \over 2}}}}$

Studies have associated ABSI with total mortality and cardiovascular risk, indicating that it is useful in assessing cardio-metabolic risks.[7]