Body fat percentage

Body fat percentage is fat mass as a share of total body weight, with the rest counted as fat-free mass.^{1International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 155.} It’s the usual way to report body composition, and includes both essential fat needed for normal function and storage fat.^{1International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 155.}

There are no universally accepted norms.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 194.} In ACSM’s skinfold-based tables, the “good” category spans 12 to 23% for men and 17 to 26% for women across a wide range of ages, though age, sex, race and athletic level affect what counts as healthy.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 194.} ACSM recommends no less than 3% body fat for men and 10 to 13% for women.^{3Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 196.}

In practice

• Report a range: skinfold assessment equations carry a standard error of at least 3 to 5%, so a 24% reading represents roughly 21 to 27%.^{4Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 265.}
• Stick to one method for retests, because results depend on how fat is measured.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 194.} DXA ranges from a US sample run higher (19 to 26% for men, 28 to 36% for women) than the skinfold-based “good” range.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 194.}
• Be wary of smartphone apps that estimate body fat from photos; they lack rigorous independent validation.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 194.}
• Women carry more essential fat, about 8 to 12% against 2 to 4% for men, so an equally lean woman will read higher.^{5Helms et al., The Muscle & Strength Pyramid: Nutrition, 2nd ed., p. 53.}