Body Mass Index (BMI) is a mathematical equation using height and weight to classify degree of body fat. BMI is a validated measure of nutritional status which can indicate overnutrition or undernutrition.
Formula
Weight in pounds multiplied by 703, divided by height in inches squared. On a calculator, multiply your weight in pounds by 703. Divide that number by your height in inches. Divide that number again by your height in inches. Example: (143 lb x 703)/(66")^2 = 23.
Weight Status
Underweight: less than 18.5
Normal: 18.5 to 24.9
Overweight: 25.0 to 29.9
Obese class I: 30.0 to 34.9
Obese class II: 35.0 to 39.9
Obese class III: 40 or greater
Disease and Mortality Risk
Too low BMI increases malnutrition or starvation risk. Too high BMI increases certain medical risks including hypertension, diabetes, high cholesterol, orthopedic problems and some cancers. Too low or too high BMI is correlated with death risk.
Pregnancy and BMI
Too low or too high BMI may contribute to the ability to get pregnant. Overweight and obesity has been linked with poor pregnancy outcome, gestational diabetes and impaired fetal well-being.
Drawbacks of BMI
BMI does not take into account body composition. Muscle mass also contributes to body weight, so someone who is muscular may classify as overweight when they are not.
References
- "Nutrition and Diagnosis-Related Care;" Sylvia Escott-Stump; 2002
- "Nutrition Concepts and Controversies;" Frances Sizer, Ellie Whitney; 2006
- "Krause's Food, Nutrition, and Diet Therapy;" L. Kathleen Mahan, Sylvia Escott-Stump; 2004
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