Body composition

Body composition measures the relative amounts of muscle, bone, water, and fat.

An individual can potentially maintain the same weight but radically change the ratio of each of the components that make up the body.

For instance, people with a high muscle (lean mass) ratio weigh more than those with the same height and waist circumference who have less muscle. Muscle weighs more than fat.

These measurements of body fat content were taken from high-level sportsmen and women of different disciplines:

  • Basketball– men 9 percent and women 13 percent
  • Cross-country skiing– men 5 percent and women 11 percent
  • Golf– men 13 percent and women 16 percent
  • Kayaking/Canoeing– men 13 percent and women 22 percent
  • Swimming– men 12 percent and women 19 percent
  • 100-, 200- and 400-meter racers– men 6.5 percent and women 14 percent
  • Boxing– men 7 percent
  • Wrestling– men 8 percent

How is body composition calculated?

Calculating body composition accurately can be a painstaking task. There are a number of accurate methods, this is just one:

First, weight is measured on standard scales. Next, volume is measured by submerging the individual in water and measuring the displacement.

The proportions of water, protein, and mineral in the body can be ascertained by various chemical and radiometric tests. The densities of water, fat, protein, and mineral are either measured or estimated.

The numbers are then entered into the following equation:

1/Db = w/Dw + f/Df + p/Dp + m/Dm

Where: Db = overall body density, w = proportion of water, f = proportion of fat, p = proportion of protein, m = proportion of mineral, Dw = density of water, Df = density of fat, Dp = density of protein, Dm = density of mineral.

Other methods include dual energy X-ray absorptiometry, air displacement plethysmography, bioelectrical impedance analysis, total body imaging (MRI and CT), and ultrasound.