New BAI Not Superior to Traditional BMI


Scientists at the German Center for Diabetes Research (DZD) have compared different methods for estimating the percentage of body fat. According to the latest results, measuring the waist circumference is more appropriate to estimate body fat percentage than the new body adiposity index, which in the study was also not superior to the body mass index (BMI). According to the study, diabetes risk can also be more precisely assessed using the waist circumference measurement.

A research team headed by Matthias Schulze of the German Institute of Human Nutrition Potsdam-Rehbrücke and Norbert Stefan of the Medical Clinic IV of the University of Tübingen has now published its findings in the journal Diabetologia (M. Schulze et al., 2012; DOI: 10.1007/s00125-012-2499-z).

Determination of the percentage of body fat
Only last year, American researchers developed a new equation* called the Body Adiposity Index (BAI). It is intended to be a simple, inexpensive and exact means of estimating the percentage of body fat.
The new index is based on a person’s height and hip circumference. Since its introduction, the BAI has received a lot of attention worldwide and is used to estimate body fat percentage by many health professionals, who assume that it provides more relevant results than the BMI.

To date, there has been a paucity of scientific data on the BAI, and therefore a research team headed by the nutrition epidemiologist Matthias Schulze and the physician Norbert Stefan compared the significance of the new index with the predictive value of hip and waist circumference measurements and also with the BMI. For this purpose, they examined the data of 138 male and 222 female study participants of the Tübingen Lifestyle Intervention Program (TULIP), the data of 9729 men and 15438 women who are participating in the EPIC-Potsdam study (European Prospective Investigation into Cancer and Nutrition), as well as 5573 male and 5628 female participants of the study Cooperative Health Research in der Region of Augsburg (KORA) **. The joint comparison of the three large-scale studies has become possible mainly through the close cooperation within the DZD.

The gold standard for comparing the different measurement methods is magnetic resonance imaging (MRI), which can very accurately determine the percentage of body fat. The research group of Fritz Schick used MRI in the Tübingen study.

BMI more closely associated with body fat distribution
“In the present study, we showed that the BAI is not superior to the traditional, well-known BMI in estimating the percentage of body fat. Moreover, the BMI is even more closely associated with body fat distribution than the BAI,” Matthias Schulze said.
“Especially in male study participants, the estimation of body fat percentage using the BAI was inexact.” Furthermore, in determining the diabetes risk of the study participants, the BMI was superior to the BAI. Strikingly, in terms of diabetes risk assessment, both indices were less significant than the measured waist circumference.

“In our opinion,” Norbert Stefan said, “the BAI cannot be considered an alternative to the BMI. However, it does make sense to measure the waist circumference in addition to the body mass index.”

Background information:
*The formula for the body adiposity index is: BAI = hip circumference in cm/(height in m)1.5 – 18 = percentage of body fat

The formula for the body mass index is: BMI = body weight in kg/(height in m)² = percentage of body fat

**Information on the Tübingen Lifestyle Intervention Program (TULIP)

Information on the Potsdam EPIC study

Information on the Augsburg KORA study