Understanding BMI and Obesity

Dr. Jeffrey Heit Health Guide
  • Many of you may have already been following my blogs on physical fitness and ways of improving and enjoying your workouts. This blog begins a new series I will be doing regarding the nemesis of physical fitness - obesity.


    Before talking about obesity and trying to figure out how to combat it, the first thing we need to do is figure out what it is and is not. In one of my past physical fitness blogs, I discussed the all important "body mass index" or BMI. Basically, this is a measure of how much weight you carry for a given height. Since there are a number of calculations involved with figuring out your own body mass index, including converting your weight to kilograms and your height to meters, I will not go into details on how to calculate it here. You can go to our BMI calculator here, plug in the numbers and see where you fall.

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    That said, how do you know if you are underweight, overweight, obese or even morbidly obese? The Centers for Disease Control (CDC) and The World Health Organization (WHO) have come up with guidelines to help us define these terms using the BMI. Generally, you are considered underweight if your BMI is less than 19.1 for women and 20.7 for men. A normal BMI range is 19-26 for women and 21-26.4 for men.


    One is considered "overweight" when their body mass index is greater than the upper range of the normal ranges mentioned previously. In order to meet the criterion for frank "obesity" one's BMI needs to be 30 or higher. Specifically, these numbers are dealing with BMI's of adults. The entity known as "morbid obesity" also known as clinically severe obesity, is defined as a BMI of greater than or equal to 40. However, one can also be labeled as morbidly obese if body mass index is 35 or higher and the individual has one or more "co morbid" conditions. These co morbid conditions can be diabetes, high blood pressure, high cholesterol or vascular disease.


    There are different and more complex definitions for those of children and we will not deal with that subject here. If you are concerned about whether your kids may be either underweight or obese, I encourage you to bring the topic up with your pediatrician, who should be monitoring BMI in your child's growth chart anyway.


    Despite these rather clear cut criteria for obesity, one must use some discretion when using them for oneself. There are variations for different individuals, body types, ethnicities etc. Some ethnicities and nationalities may have higher or lower BMI's than others. Also, individuals who are athletic, body builders, and individuals who are muscular may have high BMI's but are not fat or obese, nor do they have the same risk factors for complications of obesity that others may.


    If you are a weightlifter and particularly muscular, you may want to give yourself more leeway with BMI than your flabby cousin who is a couch potato. If you've always been short and stocky, give yourself some leeway there as well. Of course, if you're not sure, visit your primary care provider and discuss it with him or her. You'll need to take all those factors into consideration as well as getting a blood pressure check and some blood tests to determine your fasting glucose and triglyceride levels.


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    Coming up next: Why Should You Care About Obesity?

Published On: May 20, 2008