Do You Know Your BMI?

Most clients at Iron Fit in San Antonio, TX, know their BMI and its significance. BMI stands for Body Mass Index and it’s a measure of fitness. It uses the relationship between height and weight to evaluate whether a person is underweight, normal, obese class I, obese class II or is extremely obese. While it can be a wake-up call for some people, it still has flaws and isn’t the ultimate answer to whether weight loss is necessary.

One flaw is that it doesn’t account for a very muscular body.

When someone is extremely muscular, they’ll look thinner than someone who is the same height and weighs the same but isn’t muscular. That’s because a cubic inch of muscle weighs more than a cubic inch of fat tissue. Twenty pounds of fat would require a bigger container than twenty pounds of muscle. A very muscular person might appear to be overweight if you simply looked at his or her BMI, but in reality, would be very fit. It takes additional information to be conclusive about the person’s health and fitness.

How do you find your BMI?

The process is quite simple. There are charts available on the internet. In fact, your health care professional probably has one in his or her office. It’s a shortcut for the doctor. BMI uses a grid where either the weight is across the top of the chart in vertical rows and height is along the side in horizontal rows, or vice versa, and where the row with the height intersects with the row with the weight, that’s the person’s BMI number. When the number is below 18.5, it’s considered underweight, between 18.5 and 24.0 is normal and 25 to 29.9 it’s overweight. Numbers higher than that enter into the realm of obesity.

There are other variants besides the amount of muscle tissue that make BMI less predictive

People who have a larger bone structure will have a higher BMI number, even though they may be fitter. Bone structure and amount of muscle tissue aren’t the only things that need to be considered. Age, gender and how the fat is distributed also make a difference. If you’re relatively thin, but have a huge mid-section, your BMI might not reflect a problem. However, the fat that accumulates around the middle is the most dangerous type of fat for health, called visceral fat, yet the BMI didn’t identify the problem.

  • BMI is just one measure. It’s important to get a thorough assessment of health, including using waist circumference as an indicator. For men with a waist bigger than 40 inches and women with a waist bigger than 34 inches, the risk of serious conditions increases.
  • A newer method called RFM is actually a better indicator of overall health than BMI. It uses a formula that compares height to waist measurement. It can be used in conjunction with BMI.
  • Most doctors still use BMI, as do insurance companies. The reason is that it’s simply easier to do. For doctors, it’s just one starting point with observation and other indicators used.
  • Other tests to check for amount of besides BMI are either more expensive or less reliable. They include underwater weighing, MRI scans and skinfold tests.

For more information, contact us today at Iron Fit San Antonio

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