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How to Calculate BMI for a Bodybuilder

author image Gavin Van De Walle
Gavin Van De Walle specializes in nutrition and fitness and co-owns the sports nutrition supplement company, Supra Nutrition. Van De Walle earned a Bachelor of Science degree in nutrition and food science from South Dakota State University, and is a certified personal trainer.
How to Calculate BMI for a Bodybuilder
A bodybuilder using the leg press machine. Photo Credit Hlib Shabashnyi/iStock/Getty Images

In order for a bodybuilder to competitively compete, their body fat percentage must be kept to a minimal. For a bodybuilder your BMI, or body mass index, is not an accurate representation of body fat levels or percentage. BMI uses an individual's weight, which includes both fat and muscle, and height. Therefore, bodybuilders may have a high BMI but minimal body fat. For a more accurate measure of fat, a body fat caliper or underwater weighing are better alternatives.

Fat Is Essential

Fat is often seen as the enemy, but it plays a valuable role in optimal health. Storage fats help to cushion the internal organs from trauma while the essential fats are a necessity for normal physiological functioning. "Krause's Food and the Nutrition Care Process," states that 3 percent of body fat is essential for men and 12 percent for women. The essential fat is higher in women in order to support the reproductive process. Women bodybuilders who drop below 12 percent may be at risk for infertility.

Quick Pinch

The skin fold method involves pinching the skin with your fingers at the appropriate sites -- which vary by gender -- and then using a body fat caliper to measure the thickness of the underlying adipose tissue. According to the National Council on Strength and Fitness, this method is a technique based on the fact that 50 to 70 percent of stored fat is between the skin and muscle. The skin fold test requires practice trials for accurate measurements and should be performed by a fitness professional.

Hold Your Breath

You know the saying, "muscle weights more than fat?" A method called underwater weighing utilizes that exact concept to measure body fat percentage. In fact, the American College of Sports Medicine has called this method the gold standard due to its high accuracy. Underwater weighing requires a person to be submerged in a specialized tank of water where the amount of body fat dictates the results. The test can be performed at universities or hospitals, and although it can be a few hundred dollars, this can be an accurate method to track your progress annually.

Questionable Accuracy

Skeletal muscle has a high water content, whereas fat has minimal water content. The Bioelectric Impedance Analysis, or BIA, was developed on the concept that water conducts electricity better than fat. Based on the impedance strength in correlation with height and weight metrics, the BIA scale can estimate body fat percentage. According to the International Sports and Sciences Association, BIA devices tend to under-read body fat percentage. It is important to keep the questionable accuracy in mind, as many gyms have BIA weight scales.



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