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Body Mass Index Test - What The Results Mean

Aug 31, 2009

If you have taken a body mass index test (BMI) to determine your body’s composition, you most likely have been left with a few questions about what the results mean. The results of this test provide some insight into your risk factors for various health problems ranging from diabetes to high blood pressure to high cholesterol, as well as determine if you are of a healthy weight or not.

What is the Body Mass Index Test?

The BMI test assesses your weight based on your height and gives you a number that classifies you as being underweight, of normal weight, overweight or obese. It is a very useful indirect measure of your body’s composition because it relates highly to your overall body fat.

The BMI test was originally developed simply as a method to classify a person’s “fatness” or “thinness” so that doctors could more objectively discuss issues related to being overweight and underweight with patients. It has since become more readily used as a numerical authority for diagnosis that has made it quite controversial in recent years with the rise in obesity throughout the world.

To obtain results from the BMI test, you must take your weight in kilograms (kg) and divide it by your height in metres (m), and then divide the result by your height in metres (m) again.

What Do the Results Mean?

The results of a BMI test are classified into the following groups:

  • A BMI score of less than 18.5 is considered underweight
  • A BMI score of 18.5 to 24.9 is considered to be of a healthy weight
  • A BMI score of 25 to 30 is considered to be overweight
  • A BMI score above 30 is considered to be obese
  • A BMI score over 40 is considered to be morbidly obese

Being underweight, overweight and obese puts you at higher risk for developing a number of health problems, including:

  • Hypertension
  • Type 2 diabetes
  • Heart disease
  • Stroke
  • Osteoarthritis
  • Sleep apnea.
  • Gallbladder disease
  • Breast, colon and endometrial cancers

However, just because your BMI puts you in one of the categories of high risk, does not necessarily mean that you have any greater risk for these diseases than someone of a healthy BMI. If you are classified as underweight, overweight or obese, your doctor will assess your risk factors for these diseases with other predictors such as your waist circumference and physical activity level to make a more accurate diagnosis.

How Reliable are the Results?

Because the makeup of everyone’s body is unique, it is difficult to classify everyone with this test. There are many variations based on gender, race and age. Some examples include:

  • Athletes often have high BMI ratings because of their larger muscularity, not increased fat.
  • With the same BMI, women generally have more body fat than men
  • With the same BMI, older people generally have more body fat than younger people

Because the results can vary greatly based on these factors, the BMI test is only an indicator of whether or not you are in a healthy weight range. It should not be used as a diagnostic tool or as your only classification to whether or not you are healthy. Talk to your doctor about your results to determine if you are within a healthy weight range or at risk for any chronic diseases due to your weight or lifestyle.

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