General Body-fat Percentage Categories Classification Essential fat Athletes Fitness Average Obese
Women (% fat) Men (% fat) 10–13% 14–20% 21–24% 25–31%
2–5%
6–13% 14–17% 18–24%
32% and higher 25% and higher DO THE MATH
Marci is a 34-year-old client who weighs 120 pounds. Using the following skinfold measurements, calculate Marci’s body density. • Triceps: 24.5 mm • Suprailium: 12 mm • Thigh: 35 mm
Body density = 1.099421 – 0.0009929 (sum of three skinfolds) + 0.0000023 (sum of three skinfolds²) – 0.0001392 (age)
Reprinted with permission from The Cooper Institute, Dallas, TX. For more information: www.cooperinstitute.org.
Body density of fat tissue equals 0.9 g/cc3 is approximately 1.1 g/cc3
, while the density of fat-free tissue , although these figures vary slightly by age, gender,
and ethnicity. Once body density is determined, it needs to be converted to body composition. Two of the most commonly used prediction equations to estimate percent body fat are: • Brozek et al. (1963): % Fat = (457/Body density) – 414 • Siri (1961): % Fat = (495/Body density) – 450
These calculations provide generalized measurements of subcutaneous fat for an average person based on the populations that were used to establish these coefficients.
DO THE MATH
Use the Siri (1961) equation to calculate Marci’s percent body fat: % Fat = (495/Body density) – 450 = (495/1.035) – 450 = 478.3 – 450 = 28.3
