With the recent attention paid toward diets and wellness, one term that undoubtedly you will encounter is body mass index (BMI). This is a term that is commonly used to identify disease risks and, to some degree, your level of fitness. So what does this term mean?

What is BMI?

Body Mass Index or BMI is a tool for indicating weight status in adults. It is a measure of weight for height. For adults over 20 years old, BMI falls into one of these categories:

BMI Weight Status
Below 18.5 Underweight
18.5 – 24.9 Normal
25.0 – 29.9 Overweight
30.0 and Above Obese

BMI correlates with body fat. The relation between fatness and BMI differs with age and gender. For example, women are more likely to have a higher percent of body fat than men for the same BMI. On average, older people may have more body fat than younger adults with the same BMI. (1)

How does BMI relate to health?

The BMI ranges are based on the effect body weight has on disease and death. As BMI increases, the risk for some disease increases. Some common conditions related to overweight and obesity include(2):

  • Premature death
  • Cardiovascular disease
  • High blood pressure
  • Osteoarthritis
  • Some cancers
  • Diabetes

BMI is only one of many factors used to predict risk for disease. BMI cannot be used to tell a person if he/she has a disease such as diabetes or cancer. It is important to remember that weight is only one factor that is related to disease.


How to Calculate BMI?

Body Mass Index can be calculated using pounds and inches with this equation

BMI = ( Weight in Pounds) x 703
(Height in inches) x (Height in inches) )

What Does This All Mean?

BMI is not the only indicator of health risk.
BMI is just one of many factors related to developing a chronic disease (such as heart disease, cancer, or diabetes). Other factors that may be important to look at when assessing your risk for chronic disease include:

  • Diet
  • Physical Activity
  • Waist Circumference
  • Blood Pressure
  • Blood Sugar Level
  • Cholesterol Level
  • Family History of disease

Whatever your BMI, talk to your doctor to see if you are at an increased risk for disease and if you should lose weight. Even a small weight loss (just 10% of your current weight) may help to lower the risk of disease.
Physical activity and good nutrition are key factors in leading a healthy lifestyle and reducing risk for disease.

BMI does not measure body fat!

The BMI is appropriate for the general population but is not appropriate for athletes or people with a high amount of lean muscle mass. The reason being that two people can have the same BMI, but a different percent body fat. For example, a bodybuilder with a large muscle mass and a low percent body fat may have the same BMI as a person who has more body fat because BMI is calculated using weight and height only. Therefore, the BMI would not be an appropriate indicator of risk for the bodybuilder.

1. Gallagher D, et al. How useful is BMI for comparison of body fatness across age, sex and ethnic groups? American Journal of Epidemiology 1996;143:228–239.
2. Calle EE, et al. BMI and mortality in prospective cohort of U.S. adults. New England Journal of Medicine 1999;341:1097–1105.