What is Body Mass Index?

The Body Mass Index (BMI) is a method used to determine if a person is overweight or not by comparing weight to height. It’s a very popular way to assess a person’s body mass because you don’t have to do any measuring beyond height and weight and it doesn’t require any special equipment.

How To Calculate Your Body Mass Index (BMI)

The formula used to calculate BMI is weight in kilograms divided by height squared in meters.

BMI= Weight(kg) / Height Squared (m)

So, if I weigh 140 pounds and I’m 63″ tall this is how I calculate my BMI:

140 lb/2.2 = 63.64 kg

63″ X 2.54 = 160.02 cm / 100 = 1.6 m

Next, I divide 63.64 (my weight in kg) by 1.6 (my height in m) squared:

63.64 / (1.6 squared) =

63.64 / 2.56 = 24.86 rounded up to 25

Based on the formula, my BMI is 25

What Does it All Mean?

Additional official charts and references have established the following standards:

Normal Weight = BMI 19 to <25

Overweight = BMI 25 to <30

Obese = 30 to <35

Seriously Obese = > 35

So, if I were to take the Body Mass Index at face value, I’d come out of this thinking I’m an overweight individual. I’d be depressed and I’d spend a couple of days beating myself up and staring at myself in the mirror in order to pinpoint my “trouble spots”. The whole scene would be pretty pitiful and frankly, a big waste of time.

You see, here’s the problem, the numbers I used above are real numbers taken from a fitness competitor around the time she won a state fitness title. So, how is it possible that she could have been overweight, as the BMI indicates, and still in shape to win a fitness contest? Because the BMI doesn’t account for muscle mass!

The fact is that muscle weighs more than fat. So, if you’re short and muscular, you’ll weigh more than someone who’s short and fat, but your body fat percentage will be lower. However, it’s entirely possible that your BMI will be higher since the only things BMI considers are height and weight. Not body composition.

To Sum It Up For You

BMI only evaluates body weight as a whole, not estimates of body fat versus lean body mass. For this fact, the system doesn’t differentiate between those who are over-fat and those who are athletic. It’s a decent measure for the majority of the population who isn’t highly athletic or muscular, but ideally, BMI assessments will be used in conjunction with other means of body composition measurements.

Please, if you’re over weight and it’s from lack of exercise and overeating, don’t estimate your BMI and go celebrate because this article states that people with a lot of muscle can have a high BMI so you figure you must be genetically blessed with all kinds of natural muscle.

In the absence of additional methods of body composition assessments, common sense will go a long way in helping you decide whether or not you should take your calculated BMI at face value.