Is Body Mass Index a Legitimate Health Indicator?

You may have heard of BMI, or Body Mass Index, which is a measurement used to assess health by comparing your height to your weight. In technical terms, it’s your body mass divided by the square of your height and expressed in units of kilograms per meter squared. It’s been criticized fairly often because of how it only focuses on these two measurements — height and weight — when there are so many other factors that come into play in human health.

Generally, you are considered “healthy” according to BMI if your number value is between 18.5 and 24.9. You are underweight if your BMI is under 18.5, and you are overweight or obese if it is above 24.9. Pretty oversimplified, right?

You might have some questions after reading those narrow ranges. How does it take into account your frame size or bone structure? Does it take into consideration the fact that muscle weighs more than fat? No, it doesn’t. BMI is only one measurement of your health and may be distorted if your frame is smaller or larger than average or if you are a serious athlete. It might also be a bit inaccurate for teenagers, especially teen girls, who may be experiencing bodily changes during puberty.

Earlier this year, Tessa Embry, an 8th grade student from Indiana, wrote a now-viral essay in protest of her school’s use of BMI in gym class. According to the number value calculated by Tessa’s height and weight, she was classified as obese and at risk for health problems. As an athlete, who, in her own words, makes “very healthy choices,” she was taken aback by her school’s use of the measurement. After visiting her doctor, she was “given a clean bill of health,” and she refused to participate in the next assignment requiring the use of her BMI. She wrote an essay detailing how the measurement is arbitrary and outdated instead.

Does that mean BMI is completely worthless? It isn’t entirely. Tessa was right that it’s outdated and takes very few factors into consideration when determining health. It shouldn’t be used as a diagnostic tool or to shame people for their weight; but, if your values aren’t inside the recommended 18.5-24.9 range, it may be helpful to discuss your health with a doctor. Being underweight or overweight does not mean you are automatically unhealthy, just as people who are considered average weight are not necessarily healthy. But weight outside the general parameters can increase your risks for certain illnesses or indicate a need for changes in your diet.

Pretty much, just don’t worry about it too much, okay? It’s just one number when there are so many other more important things about you, and one data point isn’t enough to make any conclusions anyway. Maybe one day there will be a method in the health field to actually determine a person’s risk for diseases and overall health state with just a little bit of information on your body, but that day is probably not going to come anytime soon.

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