Body Adiposity Index (BAI) Calculator

Estimates body fat percentage based on height and hip size, being applicable across all ethnic groups.

The text below provides more information on the BAI formula, describes findings from the original study and elaborates on criticism of the index.


Because highly accurate body fat percentage measurements like dual-energy X-ray absorption (DXA) or underwater weighting are impracticable, complex and costly in most clinical settings, the body mass index may be used to estimate body fat based on two simple measurements, height and hip size.

It has been deemed by the original study and others as more accurate for different body types than the BMI but has also received criticism in further validation studies, so should be employed with caution and understanding of its benefits and limitations.


BAI formula

BAI = (Hip Circumference / (Height)^1.5) – 18

Where: Hip circumference is expressed in centimeters and height is in meters.

The resultant BAI percentage can be compared to the values in the table below (by gender and age group) to provide an indication whether the person is underweight, healthy weight, overweight or obese.

Age Gender Underweight Healthy Overweight Obese
20 - 39 Male <8% 8 - 21% >21 - 26% >26%
Female <21% 21 - 33% >33 - 39% >39%
40 - 59 Male <11% 11 - 23% >23 - 29% >29%
Female <23% 23 - 35% >35 - 41% >41%
60 - 79 Male <13% 13 - 25% >25 - 31% >31%
Female <25% 25 - 38% >38 - 43% >43%

Source: BAI classification by Gallagher et al. (2012)


Height
Hip Circumference
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Body Adiposity Index explained

The BAI formula described by Bergman et al. in their 2011 study is based on comparing height to hip size, unlike other measures of weight health status which account for body weight, and provides the percentage value of body fat.

The BAI formula is:

BAI = (Hip Circumference / (Height)^1.5) – 18

Where: Hip circumference is expressed in centimeters and height is in meters.

The resultant BAI percentage can be compared to the values in the table below (by gender and age group) to provide an indication whether the person is underweight, healthy weight, overweight or obese.

Age Gender Underweight Healthy Overweight Obese
20 - 39 Male <8% 8 - 21% >21 - 26% >26%
Female <21% 21 - 33% >33 - 39% >39%
40 - 59 Male <11% 11 - 23% >23 - 29% >29%
Female <23% 23 - 35% >35 - 41% >41%
60 - 79 Male <13% 13 - 25% >25 - 31% >31%
Female <25% 25 - 38% >38 - 43% >43%

Source: BAI classification by Gallagher et al. (2012)

The body adiposity index is suggested by many sources as an alternative to the body mass index (BMI) which has been widely criticised for not being accurate for all body types. However, the BAI has also been criticised by systematic reviews as producing biased estimates of percent body fat.

 

About the original study

Bergman et al. set out to provide a body fat percentage formula that addresses the BMI inaccuracies (amplified in cases with high lean body mass, such as athletes) and that can be universally applicable across different ethnic groups.

Highly accurate body fat measurement methods like underwater weighing and dual-energy X-ray absorption (DXA) are often impractical in routine clinical settings due to their complexity, cost, and time consumption so a straightforward to calculate index is necessary.

The 2011 study on the "BetaGene" population was validated against the "gold standard" of body fat measurement, DXA, using Lin’s concordance correlation coefficient.

The BAI measure was further validated in the “Triglyceride and Cardiovascular Risk in African-Americans (TARA)” study that was conducted on African Americans. The correlation between DXA-derived percentage adiposity and the BAI was R = 0.85 for TARA, with a concordance of C_b = 0.95.

The original study concluded that the BAI can serve as a reliable measure for percentage body fat for adult men and women of diverse ethnic backgrounds.

 

BAI Criticism

Freedman et al. compared the prediction of percent body fat, as assessed by dual-energy x-ray absorptiometry (PBFDXA), by BAI, BMI, and circumference (waist and hip) measurements among 1,151 adults who participated in studies conducted at the Body Composition Unit of the New York Obesity Nutrition Research Center between 1993 and 2006. The study population had had a total body scan by DXA and circumference measurements.

PBFDXA was related similarly to BAI, BMI, waist circumference, and hip circumference. In general, BAI overestimated PBFDXA among men (3.9%) and underestimated PBFDXA among women (2.5%) so the errors of BAI estimation of percentage body fat vary by gender and level of body fatness.

A BAI validation study conducted by Cerqueira et al. on samples on individuals from different continents, varied ethnicities, both sexes, and a wide age range (18–83 y), found that the concordance of the BAI with DXA assessed by Lin's concordance correlation coefficient showed results classified as poor (pc <0.90).

Bland-Altman plots showed that the BAI produced large individual errors when predicting BF% in all studies (samples from 19 studies were included).

Cerqueira et al. conclude that the BAI shows wide individual errors, in agreement with the reference method, and a lack of sensitivity in detecting change in BF% over time.

The BAI consistently overestimates body fat percentage (BF%) in individuals having 20% or less body fat, and underestimates in those with more than 30% body fat. This error pattern persists irrespective of the individual's sex, age, or ethnicity.

Indexes of body fat that incorporate measurements of the waist, such as the waist-to-height ratio (WHtR), might offer superior evaluation of metabolic and cardiovascular risk in comparison to the BAI and the BMI. This holds true for both clinical settings and research.

 

References

Original reference

Bergman RN, Stefanovski D, Buchanan TA, Sumner AE, Reynolds JC, Sebring NG, Xiang AH, Watanabe RM. A better index of body adiposity. Obesity (Silver Spring). 2011; 19(5):1083-9.

Other references

Gallagher D, et al., Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index, The American Journal of Clinical Nutrition, Volume 72, Issue 3, September 2000, Pages 694–701.

Cerqueira MS, et al., Validity of the Body Adiposity Index in Predicting Body Fat in Adults: A Systematic Review, Advances in Nutrition, Volume 9, Issue 5, September 2018, Pages 617–624.

Freedman DS, Thornton JC, Pi-Sunyer FX, Heymsfield SB, Wang J, Pierson RN Jr, Blanck HM, Gallagher D. The body adiposity index (hip circumference ÷ height(1.5)) is not a more accurate measure of adiposity than is BMI, waist circumference, or hip circumference. Obesity (Silver Spring). 2012; 20(12):2438-44.


Specialty: Fitness

Type: Index

No. Of Variables: 2

Year Of Study: 2011

Abbreviation: BAI

Article By: Denise Nedea

Published On: June 6, 2023

Last Checked: June 6, 2023

Next Review: June 6, 2028