Jennifer Fields, assistant professor of nutritional sciences, has developed an equation to allow coaches, trainers, and anyone else working with athletes to gain a more accurate, accessible measurement of body composition
Photo by Chau Cédric on Unsplash
Body composition – a measure of the proportion of fat, muscle, and bone that make up your body weight – is an important metric of health.
Body fat percentage in particular can help determine health outcomes. And for athletes, who have more muscle than the average person, an accurate measure of what percent of their weight is fat is an important indicator of overall fitness and progress.
"It's a way that we assess progress and adaptation to training in our athletes," Jennifer Fields, assistant professor of nutritional sciences in the College of Agriculture, Health and Natural Resources, says. "If [we have an assessment] that's giving us false information, we can't strategically analyze the training and nutrition programming to make sound decisions about the adaptations that the athletes are experiencing."
The gold standard for assessing body composition is a dual-energy-X-ray absorptiometry (DXA) scan. However, DXA scans are expensive, require technical licenses, and, because they emit radiation, cannot be used during pregnancy and other sensitive cases.
There is another method of measuring body composition called the "Bod Pod." This technology is much more accessible, and while still considered a valid measure of body composition metrics, can be less accurate for athletes. Bod Pod calculates body density. From that measurement, it uses a predictive equation to calculate body fat percentage. Studies have found that Bod Pod tends to underestimate body fat percentage in very lean individuals and may overestimate it for larger athletes.
"The problem with those predictive equations is they were developed in general populations," Fields says. "Body composition of athletes tends to differ drastically from non-athletes. Athletes are much leaner. They have much greater amounts of fat-free mass."
Fields has developed an equation that allows coaches, trainers, and anyone else working with athletes to easily convert Bod Pod readings into a more accurate measurement.
This work was published in the Journal of the International Society of Sports Nutrition.
Fields and her collaborators used a sample of 130 athletes from men's and women's basketball, women's tennis, women's and men's soccer, women's lacrosse, and baseball.
The researchers measured body composition on 100 of these athletes using Bod Pod and then a DXA scan. The other 30 were used to cross-validate the equation and received only a DXA scan.
The equation works by subtracting the body density score provided by the Bod Pod from a constant developed by the researchers. Then, users plug the resulting number into the equation to get an accurate measure of body fat percentage.
The researchers found that their equation provides the same body fat percentage measure as a DXA scan. Without the developed equation, the Bod Pod predicted body fat percentage at 17.7%, compared to 21% produced by the DXA. However, their equation produced a body fat percentage of 21%, exactly that of the DXA.
Many college athletics programs have a Bod Pod available, making this approach directly applicable.
The next step for this work is to test the equation with a larger sample that will also allow the researchers to see if there are factors like sex, sport, age, or race that may influence the equation's accuracy.
"This was really one of the first studies to say, OK is there a correction we can make?" Fields says. "Because some of these validated equations that the Bod Pod uses just may not be applicable for athletic populations."
This work relates to CAHNR's Strategic Vision area focused on Enhancing Health and Well-Being Locally, Nationally, and Globally.
