Facts on File Encyclopedia of Health and Medicine

Methods for measuring or approximating body
fat percentage include

• BODY MASS INDEX(BMI), a mathematical formula
  based on weight and height


• skinfold calipers, which measure the thickness
  of a fold of SKIN(typically at the triceps on the
  back of the upper arm) to determine the
  amount of subcutaneous fat


• bioelectrical impedance, which measures the
  resistance a mild electrical current encounters
  when passed through the body


• hydrostatic weighing, which uses water dis-
  placement to determine body mass

Additional measures that improve the precision
of body fat percentage estimates include WAIST CIR-
CUMFERENCEandWAIST TO HIP RATIO, as these meas-
ures increase with excessive body fat. Dual-energy
X-RAYabsorptiometry (DEXA), an X-ray procedure
to determine BONE DENSITY as an assessment of

OSTEOPOROSIS, also provides calculations of body fat

percentage and lean tissue mass. No single method

provides an absolute measure of body fat percent-

age.

See also DIET AND HEALTH; EXERCISE AND HEALTH;

FITNESS LEVEL; UPPER ARM CIRCUMFERENCE; WEIGHT

LOSS AND WEIGHT MANAGEMENT.

body mass index (BMI) A mathematical meas-

ure of total body size and its correlation to health

risk. BMI values derive from height (without

shoes) and weight (without clothes) measures,

with mathematical calculations that convert those

measures to a value that reflects overall body size.

BMI represents the mass of the body in kilograms

per meter squared (kg/m^2 ) though the common

presentation of BMI is simply the numeric value.

A low or a high BMI corresponds with increased

risk for numerous health conditions. A BMI of 25

or greater is overweight; a BMI of 30 or greater is

OBESITY. BMI values apply to men or women who

have the same measurements. For example, a

body mass index (BMI) 289

BODY FAT PERCENTAGE AND HEALTH RISK

Health Status Men Women
at risk forNUTRITIONAL DEFICIENCY < 4 percent < 12 percent

lean (athlete or high fitness level), 4 to 15 percent 12 to 22 percent
no increased health risk

healthy, no increased health risk < 20 percent < 27 percent

overweight, moderate increase 20 to 25 percent 27 to 32 percent
in health risk

OBESITY, significant increase in health risk > 25 percent > 32 percent

BMI AND HEALTH RISK

BMI Classification Health Risk Due to Weight

18.5 underweight may indicate EATING DISORDERSor undernutrition
19 to 24.9 healthy weight no increased health risk
25 to 29.9 overweight moderate health risk
30 to 34.9 OBESITY, class 1 significant health risk
35 to 39.9 obesity, class 2 high health risk; INSULIN RESISTANCEor CARDIOVASCULAR DISEASE(CVD) likely
40+ obesity, class 3 severe health risk; DIABETES, CVD, or HYPERTENSIONlikely