Encyclopedia of Health and Medicine

ody mass index (BMI) 289
BODY FAT PERCENTAGE AND HEALTH RISK
Health Status Men Women
at risk for NUTRITIONAL 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
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 displacement
to determine body mass
Additional measures that improve the precision
of body fat percentage estimates include WAIST CIR-
CUMFERENCE and WAIST TO HIP RATIO, as these measures
increase with excessive body fat. Dual-energy
X-RAY absorptiometry (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 percentage.
See also DIET AND HEALTH; EXERCISE AND HEALTH;
FITNESS LEVEL; UPPER ARM CIRCUMFERENCE; WEIGHT
LOSS AND WEIGHT MANAGEMENT.
body mass index (BMI) A mathematical measure
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
BMI AND HEALTH RISK
BMI Classification Health Risk Due to Weight
> 18.5 underweight may indicate EATING DISORDERS or 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 RESISTANCE or CARDIOVASCULAR DISEASE (CVD) likely
40+ obesity, class 3 severe health risk; DIABETES, CVD, or HYPERTENSION likely