Body Mass Index vs. Body Fat Percentage


 (DGIwire) — Body Mass Index (BMI) and Body Fat Percentage (BF%) are often confused and even used interchangeably. However, they are not the same, and people need to understand the difference in their usefulness for health assessment.

There is a health correlation between height and weight in the general population. BMI is a number that is based on height and weight. The BMI ranges are based upon data derived from looking at a vast number of people. Doctors across the country use and discuss BMI with patients as a guideline for a healthy weight and reduced risk of certain diseases, especially heart disease and diabetes. For most people, BMI will give an indication of where they currently are—if a look in the mirror has been ignored.

The flaw with BMI is that uses total weight and does not consider actual body composition—lean body mass and fat. It is entirely possible for two people of the same height, weight and BMI to have very different body compositions. An inactive person will generally have more body fat than an active one. Therefore, a BMI in the recommended range for one’s height and current weight is not necessarily a clean bill of health. In fact, it has been noted that health problems start increasing in a linear fashion as BMI rises above 19.

Body fat is the only thing we want to lose when reducing our overall weight. Since most traditional diets also result in loss of lean body mass, a lower BMI might not actually result in an equally lower risk of disease or a lean body if one’s BF% remains the same. Many dieters lose weight but just end up looking like a smaller version of their former selves because their body composition has not changed significantly. They do have less fat than before, but they also have less muscle and other critical tissue. BMI serves a general purpose in helping someone recognize that they are overweight and at greater risk of disease, but it is almost useless as a tool in a weight/fat reduction program.

For any diet effort to be successful, it is critical to know one’s starting BF% and how it relates to one’s overall body composition, and people need to have a method of monitoring it. If one’s BF% is not decreasing, the diet is not working and the person is losing critical lean body mass. When a person is losing only body fat, the change is obvious and comes quickly.

“Body composition can be compared to the power-to-weight ratio of a high-performance automobile—the higher the horsepower and the lower the weight, the greater the overall performance will be,” say boomer generation health experts Dian Griesel, Ph.D., and Tom Griesel, authors of the books TurboCharged: Accelerate Your Fat Burning Metabolism, Get Lean Fast and Leave Diet and Exercise Rules in the Dust(April 2011, BSH) and The TurboCharged Mind (January 2012, BSH). “Likewise, the more muscle we have and the lower our excess weight—i.e., body fat—the better our performance and health will be.”

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