The Body Mass Index (BMI) is a method to assess whether an individual maintains a healthy weight based on their height and weight. It classifies individuals into various categories, from underweight to obese.
However, many medical professionals and experts express reservations about the comprehensive utility of BMI. While it can offer valuable insights in certain scenarios, it doesn’t universally apply. Experts unanimously advise against relying solely on BMI and emphasize the importance of considering multiple factors when determining an individual’s ideal weight range. For instance, if an individual’s BMI falls outside the normal range, healthcare providers may additionally assess factors such as skinfold thickness (indicating body fat), waist circumference, dietary habits, family health history, blood sugar levels, and other elements to evaluate potential health risks associated with their weight.
BMI is used to broadly define different weight groups in adults 20 years old or older.
- Underweight: BMI is less than 18.5
- Normal weight: BMI is 18.5 to 24.9
- Overweight: BMI is 25 to 29.9
- Obese: BMI is 30 or more
You can also calculate your own BMI. The actual formula to determine BMI uses metric system measurements: weight in kilograms (kg) divided by height in meters, squared (m2).
When using pounds and inches, the formula needs to be altered slightly. Multiply your weight in pounds by 703. Divide that by your height in inches, squared:
BMI = (your weight in pounds x 703) ÷ (your height in inches x your height in inches)
For example, if you weigh 120 pounds and are 5 ft. 3 in. (63 in.) tall:
BMI = (120 x 703) ÷ (63 x 63) or 84,360 ÷ 3969 = 21.3
This is well within the healthy weight range.
Some examples
This table shows us that a woman who is 5 ft. 4 in. tall is considered overweight (BMI is 25 to 29) if she weighs between about 145 and 169 pounds. She is considered obese (BMI is 30 or more) if she is closer to 174 pounds or more.
A man who is 5 ft. 10 in. tall is considered overweight (BMI is 25 to 29) if he weighs between about 174 and 202 pounds, and is obese (BMI is 30 or more) if he is closer to 209 pounds or more.