What is my BMI – Should I Care?

What is your BMI, or Body Mass Index? It is ratio of you weight vs your height.

weight[lbs]/(hieght[in] X height[in]) = BMI

Generally, it is the quickest and easiest way to assume fat level and health by averaging out the BMI of a population and based above these averages giving estimates on who is overweight. Are you the same as any other person of the same sex and age? The answer is no, everyone is individual so BMI holds no more weight in the real world then estimating the amount of jelly beans in a jar based on other jars.

According to  BMI the girl on the left would be considered to be “healthy” and the man on the right to be “over-weight”. This is due to the fact that BMI does not account for body composition (or the % of muscle, bone and organs vs. fat). Muscle weighs more than fat so this man’s weight would be more then the average for his height according to the BMI standard. To understand why this would occur, you need to understand the concept of “over-fat” v. “over weight”.

“Over-fat” is a more accurate Measure of health. For men having more then 25% body fat is considered “over-fat” and for women 35%. Body Composition tests also account for underweight individuals. This provides a more accurate reading because it accounts for body type and for the diversity in individuals. In other words, some people are just slimmer then others but that does NOT mean they are healthier.

Proper ways to determine the amount of unnecessary fat (fat not necessary for human survival) include:

  • Hydrostatic weighing: calculates the difference between weight on land and weight in water under the theory that fat floats

  • Skinfold measurements: measures subcutaneous fat

  • Bioelectrical impedence:  based on how fast fat or lean body mass(muscle) can conduct a current

These tests can be conducted at some fitness clubs or by a doctor.

Once your personal body mass is identified (lean body mass v. fat weight) you can determine an ideal body weight and from there calculate the amount of pounds needed to be lost in order to achieve that ideal body weight.

So in conclusion, the BMI test is a ratio between weight and height that is then averaged against the population based upon your age and sex. It is not a true calculation of fat or obesity for most. A more individualized approach would be to find out your own body composition and consult with an expert once you have obtained your results. Work towards HEALTH versus an image we perceive to be healthy.