BAI: A New Way to Measure Body Mass

Summary
Percentage of body fat can be determined accurately with the help of techniques like dual X-ray absorption. But these techniques are not useful in a clinical setting. Instead, body mass index (BMI) is an established measure of amount of body fat used in clinical setting. This study defined a new index called body adiposity index (BAI) and found it to be a better predictor of body fat than BMI. Body adiposity index is simple to calculate; it just requires a measuring tape to determine height and hip circumference. After further validation, BAI might be applied in all ethnic groups.

Introduction
Obesity is associated with diseases like diabetes mellitus, cardiovascular disease, hypertension and cancer. There has been an alarming rise in the incidence of obesity. There are various accurate methods of recording body fat, such as underwater weighing and dual-energy X-ray absorption. But such techniques are not suitable for everyday clinical practice because of their complexity and the high costs involved. Body mass index (BMI) is the ratio of weight to height squared. It is used in clinical practice and epidemiological studies. But BMI too has its limitations. For example, estimation of BMI is often inaccurate in athletes. In children and people with more muscle mass, amount of body fats is also difficult to determine by BMI. This study examined the feasibility of a new index of body fat level and tested its applicability.

Methodology
* The BetaGene study was performed including 1,733 Mexican-American subjects who were either patients with gestational diabetes mellitus or people with normal glucose levels.
* These participants underwent dual-energy X-ray absorption examination to determine the body fat percentage.
* The link between the amount of fat in a participant and specific subject characteristics like sex, age, height, weight, waist and hip circumference was studied.
* These findings were applied to 223 African-American participants from another study (Triglyceride and Cardiovascular Risk in African-Americans, or the TARA study) to test if they could be generalized.

Results
* The percentage of body fat calculated by dual-energy X-ray absorption examination was correlated with body measurements.
* Body fat percentage was highly correlated with hip circumference but negatively correlated with the height of an individual.
* A new index called BAI was defined, based on hip circumference and height. This index could predict the body fat percentage with more accuracy.
* Finally, the BAI was calculated and tested for the African-American participants from TARA study. It was found that in this ethnic group also, BAI could accurately predict the body fat percentage much better.

Next steps/Shortcomings
Body adiposity index (BAI) was developed for Mexican-Americans and validated in African-American participants. Whether it can be applied to a Caucasian group is a question that remains to be answered. Rather than the amount of total fat in a body, the fat stored in internal organs like liver (called visceral fat) is considered a health risk for cardiovascular diseases. Whether BAI reflects the amount of visceral fat correctly is yet to be determined. More research is needed to address these issues.

Conclusion
The study has defined a new index for determining the body fat amount. It is simple to calculate and does not require even a weighing scale. This is an advantage in remote environments. The study included Mexican-American participants from Los Angeles. So the authors of this study feel that it is possible to extend the results to several populations in Central and South America. The most commonly used index for determining the amount of body fat now, BMI, has some limitations. The new index defined by this study, called BAI, is found to predict amount of body fat more accurately than BMI. It seems that BAI has a potential to be used universally.

For More Information:
A Better Index of Body Adiposity
Publication Journal: Obesity, March 2011
By Richard N. Bergman; Darko Stefanovski; Keck School of Medicine, University of Southern California, Los Angeles, California

*FYI Living Lab Reports Are Summaries of the Original Research.


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