What is a Body Mass Index? Are You Overweight?

Body Mass Index is used to measure body fat based on height and weight. It applies the same value for both adult men and women. Body Mass Index assesses whether an individual is underweight, normal, overweight or obese. It is inexpensive and easily calculated by using a chart method which can be readily found on the internet or in a physician's office. The caveat to this is that there usually is not an explanation attached to it.

This is where I have a personal involvement, as a practitioner in the medical field I am constantly asked when the chart is reviewed, "What do these numbers actually mean?"

If you have looked at these charts many only have a height listed vertically and weight horizontally, then when those are matched up there is a numerical value that coincides with it. There is no explanation as to what these numbers mean. Some may give brief explanations such as over 25 equals overweight. However this does not explain other factors for instance that if a person has a high BMI other tests should be performed to evaluate excess weight as a health risk. These assessments might include skin fold thickness measurements, evaluations of diet, use of tobacco or alcohol, physical activity, family history, age, sex and other appropriate health screenings. It should also be known that women tend to have more body fat then men, the older population may also have more body fat then the younger and the athletic individual may have a higher BMI because of increased muscle rather than body fat.

I generally tell people who question the BMI that there are other factors to consider, however this screening test is still considered one of the most accurate tests to measure the risks of health disease. The higher the BMI the higher the risk is to develop heart disease, high blood pressure, diabetes and other disease processes.

I put this out there because I see many individuals looking at this chart and often question the validity of it, since most of the population will fall into the overweight category and yet feel as if they are not. Such as the gentleman who is 5'9" weighing 170lbs in his 40's and states that he feels "great" will fall into the overweight category if solely basing this on a numerical value. This holds true for many who fall into the 25-30 range (overweight). Out of 100 people in my office setting 72 had a BMI range of 25-30, when asked if they felt they were overweight approximately 14 answered yes whereas the others felt they were in a normal range.

So in conclusion it is difficult just to tell someone "you are overweight," other factors should be considered when looking at this chart if not than all it becomes is a chart and nothing more.