Body Mass Index vs Body Fat: Measurements of YOUR Health!

As you well know, the only real way to gauge success is to measure your progress periodically. In the fitness world, there are several assessments that can aid as a yardstick for your personal achievements. Similarly, there are other measurements that indirectly measure your “risk” of developing certain weight-related medical conditions. In this blog, I will address two common measurements that are currently used to assess weight-related health risks: Body Mass Index (BMI) and body fatness.

BMI is simply a ratio of a person’s height and weight. These two factors are plugged into a fancy equation and the resulting number is your BMI value. BMI values are used to determine how your weight can affect your overall health status. The Center for Disease Control (CDC) has defined these ranges for BMI values in adults:

Underweight = Less than 18.5
Recommended = 18.6 to 24.9
Overweight = 25 to 29.9
Obese = Greater than 30

It is widely accepted that as your BMI goes up, so does your risk of developing weight-related diseases such as diabetes and heart disease. However, there are arguments that BMI is not the gold standard in determining a person’s overall health. For example, BMI values do not distinguish between muscle and fat. Therefore, highly trained athletes often fall in the overweight or obese categories for BMI despite having very low body fat. Those who argue that BMI is too broad and just a general measurement of risk, suggest that assessing body fat is a more accurate indicator of health. Determining how much fat your body has can paint a more accurate picture of your health.

So how much fat is too much? According to the American Council on Exercise, acceptable/unacceptable body fat ranges are:

Women Men
Essential Fat 10-12% 2-4%
Athletes 14-20% 6-13%
Fitness 21-24% 14-17%
Acceptable 25-31% 18-25%
Obese Over 32% Over 26%

Body fat can be measured by several different methods. A common method used by doctors and personal trainers is by using skinfold measurements and calipers to measure body fat. Calipers are used to measure body fat at specific body sites. These measurements are then compared to a chart to estimate overall body fat. The problem with this method is accuracy is dependent on the skills of the individual doing the measurements – which can vary greatly. Bioelectrical impedance analysis, another common method, is the technology behind the many fat percentage scales sold for home use. This method basically uses a weak electrical current to estimate body fat, muscle, and total body water. Another less common method is using water displacement tests to measure body fat. While this method is arguably more accurate, it is much more complicated and also not as available as other measurement techniques. The bottom line is that body fat measurement accuracy can vary greatly, as much as +/- 10% in some cases based on user error or measurement flaws.

The “take home” message is to understand the different ways we can assess overall health. While both BMI and body fat measurements provide great insight into the health of our body, they both have their drawbacks. However, both measurements provide us with a way we can assess progress and success – which is absolutely essential to maintaining a healthy lifestyle…for life!