Body Roundness Indicator (BRI) outperforms BMI, waist circumference, and hip circumference in predicting percent body fat, total visceral adipose tissue & health risk
http://www.pbrc.edu/research-and-facult ... roundness/About the Model
Geometrical Concept
Any index that serves as a proxy for percent total body fat is combining measures that identify the geometry of the human body. For example, body mass index (BMI), is developed by approximating the human body by a cylinder [1]. Similar to this concept, the developed formulas housed within this program apply elliptical models to capture human body geometry.
Body Roundness Index
First introduced in 1609 by the German astronomer Johannes Kepler to quantify the circularity of planetary orbits, the degree of roundness of anellipse is characterized by a non-dimensional value referred to as eccentricity [2]. Eccentricity valuesforan ellipse range from 0 to 1. Values closer to zero indicate that the ellipse is morecircular in shape and values closer to one are represented by tall narrow ellipses. Because the eccentricity of the human body ranged from 0.95 to 1, it is difficult to differentiate between different eccentricities without comparing numbers with high decimal place values. To decrease this burden, we mapped eccentricity to values between 1-20, where 1 represents more narrow body types and 20 represents more round body types. We refer to these values as the body roundness index (BRI).
The body roundness based prediction models of total percent body fat and total visceral adipose tissue.
Several large databases that contained total percent body fat and MRI assessed visceral adipose tissue volume were utilized to develop models that use body roundness to predict body fat and visceral adipose tissue mass. As a stand-alone prediction index, the BRI outperforms traditionally applied indices such as BMI, waist circumference, and hip circumference. The models additionally improve accuracy of prediction by including the effects of age, height, race, gender, and weight.
The geometrical measurements (height, waist circumference, and hip circumference) were applied to output your BRI and the generation of your personalized elliptical graph. The green zone that depicts healthy body roundness index were determined from published healthy body fat cutoffs [3] and a data-generated formula relating body fat and BRI.
References
1. Heymsfield, S.B., et al., Body circumferences: clinical implications emerging from a new geometric model. Nutr Metab (Lond), 2008. 5: p. 24.
2. Kepler, J., Astronomia nova. 1609, (Pragae).
3. Gallagher, D., et al., Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. Am J Clin Nutr, 2000. 72(3): p. 694-701.
Frequently Asked Questions
Q: How does the calculator determine how round I am?
A: We use your height and waist circumference to produce an oval (also known as an ellipse) to approximate your body shape. Then we calculate how close the oval is to being a circle using a number called eccentricity. There is more detailed information about eccentricity on the tab titled “About this model”.
Q: How was the healthy zone in the diagram computed?
A: We used equations that relate roundness to percent fat and determined the green ranges by substituting in the healthy age-dependent body fat ranges published in [1].
Q: What is being estimated in total percent body fat?
A: Total percent body fat represents the percentage of your total body mass that is fat mass. Note that this number does not tell you have fat mass is distributed. Fat mass is distributed differently in different individuals. This distribution depends on many factors such as age, height, gender, physical activity levels, and diet.
Q: What is visceral adipose tissue?
A: Visceral adipose tissue is located inside the abdominal cavity and surrounds internal organs like the liver and the intestine. Excess fat storage in this depot leads to a high waist circumference and is often referred to as abdominal fat distribution or belly fat. High amounts of visceral adipose tissue is closely related to type 2 diabetes, cardiovascular disease (e.g. the risk of heart attack and stroke), and increased mortality. [2, 3].
Q: Is waist circumference a sufficient input in the calculator to get a good prediction?
A: Waist circumference predicts total percent body fat fairly well (over 88% of the variance is explained by including waist circumference) and percent visceral adipose tissue (70% of the variance is explained), however, including hip circumference raises the accuracy of the prediction. We highly recommend entering both if possible. We recognize that a completed experiment may not have access to hip circumference and may still want to analyze data using the calculator, which is why we have this option.
Q: Why do I need to include my race?
A: We found that race is a factor for predicting body fat and visceral fat. Including your race will allow for the most accurate prediction of your percent body fat and percent visceral adipose tissue without directly measuring you using clinical methods. None of the inputted information is recorded, tracked, or saved.
Q: I am out of the zone. What can I do?
A: You should bring this information to your doctor or health care provider to find out what the best strategies may be to improve your health.
References
1. Gallagher, D., et al., Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. Am J Clin Nutr, 2000. 72(3): p. 694-701.
2. Kuk, J.L., et al., Visceral fat is an independent predictor of all-cause mortality in men. Obesity (Silver Spring), 2006. 14(2): p. 336-41.
3. Despres, J.P., Cardiovascular disease under the influence of excess visceral fat. Crit Pathw Cardiol, 2007. 6(2): p. 51-9.
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