How To Calculate Your BMI

In order to achieve your goals, you have to know where you’re at right now and find a way to measure your progress. BMI is a tool that helps you do both. At UpFit Academy in New York, NY, we do use BMI to help calculate both things, but it’s just one way to both identify your present fitness level and track your progress. It’s not necessarily the best way, either. BMI stands for body mass index and it uses both your height and weight to create a ratio that identifies whether you’re underweight, normal, overweight or obese.

The process is simple and it’s one reason most doctors use it.

There are a number of charts available, but they all use the same format. Weight is either across the top or down the side, with height taking the opposite position. In most cases, height creates rows down the side and weight creates columns across the top. Some charts are gender specific, some are specifically for children. All work the same way. You locate the person’s weight, normally at the top, find the height, normally at the side and where the column and row intersect, that number is the BMI. BMI numbers below 18.5 are underweight and 25, above overweight and 30 and above obese.

It’s a quick way to create a mental image but has many flaws.

Most people that are involved with fitness understand that when you’re comparing two people with the same bone structure, the same height, the same gender and the same weight, but one is extremely muscular and the other has almost no muscle, the muscular person will look far thinner. That’s because muscle tissue weighs more per cubic inch than fat does, so a pound of muscle mass will fit into a smaller container than a pound of fat. That fact affects the quality of the results of the BMI. An extremely muscular person, who has little body fat, may show up on BMI charts as overweight and in extreme cases, obese. In reality, they’re simply muscular.

You need other tools to make the right assessment.

Doctors use BMI because it’s quick and over time, tracking BMI can be an indicator in health. If someone has a normal BMI that suddenly drops to underweight or increases to obese, something may be wrong with that person. It’s another clue into the person’s health but needs follow-up questions. Is the person trying to lose weight? Are they now working out? Do they have a health issue that’s causing weight loss or weight gain and are there other indicators, like an increase in blood pressure or high blood glucose levels, which require further exploration? Is the BMI constantly increasing or relatively level?

  • Using a waist circumference is another tool that’s simple. If you carry your weight around the middle, you’re at more risk of serious conditions. Women with a waistline of 34.6 or more or men with a circumference of 40.2 inches are at risk.
  • One reason for using gender specific charts is the difference in bone structure and muscle mass in men and women. On the average, men tend to have a larger bone structure and more muscle mass.
  • RFM—relative fat mass—is a new quick indicator that considers amount of muscle. For men, the formula is: 64 – (20 x height/waist circumference) = RFM and for women it’s: 76 – (20 x height/waist circumference) = RFM.
  • Regularly taking body measurements, measuring body fat with skinfold calipers and even using clothing size are inexpensive techniques to identify progress. More expensive techniques include MRI scans and underwater weighing.

For more information, contact us today at UpFit Training Academy

Leave a Reply