Understand Your BMI and Body Fat Percentage

30 06 2011

By Kisar S. Dhillon
For Active.com


Understand your BMI (Body Mass Index) and Body Fat Percentage to set proper goals and determine what’s healthy for you.

Body Mass Index (BMI)

The term Body Mass Index (BMI) is not just used in doctor’s offices or health and wellness facilities, but it is also widely used in the insurance industry. To understand this popular measurement, you need to know how it is calculated. Body Mass Index is basically a height to weight ratio.

Formula: BMI (lbs/inches2) = (weight in pounds x 703) / (height in inches) ²
The benefit for using this formula is that you can calculate a large demographic of individuals in a short amount of time and get a good estimate of their overall health risk. The downfall of using this measurement is that it does not take into consideration those individuals who have a low percentage of body fat, a high percentage of lean body mass, or fitness level. A great example would be a professional football player who is 6 feet tall, weighs 250lbs and is 8.5 percent body fat. According to the BMI calculation, this person would have a BMI of 34 and be considered “obese”, when clearly that is not the case.

As a word of caution for the individuals who are very active and play competitive sports (at all levels), the BMI may not be a great choice when measuring your overall health.  However, calculating your body fat percentage instead may provide some feedback.


Body Fat Percentage


Body Fat Percentage is how much of your body is composed of fat (adipose tissue) and how much of your body is composed of muscle, bone, internal organs, skin, tissue, hair, etc. The dilemma is selecting what type of equipment or test to use to calculate body fat percentage. There are various methods such as Bioelectrical Impedance Analysis (BIA), Infrared Analysis on the Bicep, Skin Fold Calipers, and Hydrostatic Weighing.

The one variable that you need to take into consideration is that all of these tests have a standard of error. To keep that error to a minimum, make sure that all the equipment is correctly calibrated, properly maintained, and that the same individual who does the initial measurement also does the follow-up tests. If you use different individuals to measure your body fat every few weeks or months, the data may be compromised because of improper training or by changing the testing site on your body.

When it comes to hydrostatic weighing and calculating body fat percentage, this measurement is ideal, but it can be tricky. This test is done by submerging yourself underwater, and then expelling all the air out of your lungs in order to get a true measurement. The variable that creates a small percentage error is the amount of residual air volume that is left in your lungs when trying to expel all of your air out. If you have the chance to try hydrostatic weighing, I would strongly encourage you to do so, but if it is not feasible, then the other types of measuring body fat percentage will do, just be consistent with who does the measuring and that the equipment is working properly.

Both your BMI and Body Fat Percentage are great tools to assess overall health risk, but they need to be selected based on who is getting measured, what is the purpose of the measurement and what is the ultimate goal of the result you achieve.




Kisar Dhillon is a professional fitness trainer living in Orange County, California. He holds a Bachelor of Science Degree in Kinesiology, Post Baccalaureate Studies in Exercise Physiology and a Masters in Business Administration. He has more than 16 years in the health & fitness industry and is currently the owner of 1-2-1 Fitness, LLC.





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