If you’ve been frequenting the gym or went to a physicians office lately, you might have seen a BMI chart on the wall. Some people will tell you that the BMI chart is complete nonsense, while others continue to look at it for information. Even with BMI getting slammed by fitness gurus and medical professionals for not measuring health accurately, there’s a reason why you should still take a look at your BMI range.
BMI, which stands for “Body Mass Index,” has been used for over a century for figuring out whether people are under or overweight. While the BMI is imperfect, understanding where your body fat is when compared to your height and weight can help you understand just how healthy you really are.
What is the Body Mass Index?
The Body Mass Index (BMI) is medically defined as the measurement of a person’s weight divided by their height. BMI is thought to correlate with the total body fat present on someone’s body, meaning that as the BMI score rises, so too does the total body fat.
The World Health Organization (WHO) states that an adult who has a BMI between 25 and 29.9 as overweight, 30 or higher to be considered obese, and a BMI that is 18.5 or lower to be underweight. Therefore, the ideal range on a BMI chart would be 18.5 to 24.9 points.
How To Calculate BMI
Calculating your BMI is very easy. There’s a number of calculators available online, but if you prefer to do the math yourself, the equation is:
BMI = (Weight (lbs) / (Height (in))^2) x 703 (kg/m^2)/(lb/in^2)
Because BMI is originally represented by kg/m^2, it might be smarter to convert the pounds and inches over to kg and meters, which makes the equation look like this:
BMI = Weight (kg) / (Height (m))^2
For example, if you weigh 58.9kg (130 pounds) and are 1.67 meters tall (5’6”), your BMI would be around 20-21 points.
According to a standard BMI chart, this individual would be underweight. But is that accurate? Let’s break it down with the good, the bad, and the ugly facts about BMI.
The Good About BMI
BMI works well when it is used as it was supposed to be: to measure the rate of obesity in a group. Because BMI is a measure of generalized obesity in a population, the BMI levels of body fat percentage have changed throughout the years. Similarly, because it’s an easy way to take measurements on body fat, many researchers use BMI when gathering data for more detailed investigations that might look into how obesity affects a certain group of people.
In terms of the general population, however, BMI can be a useful tool for indicating whether or not someone is underweight, overweight, or obese. Due to the simplicity of calculating one’s BMI, it is easy to gauge your health, or the health of someone else, relatively quick. Children and teenagers can also use the BMI scale, but adolescence may skew the results since girls tend to put on more fat as they go through puberty than men.
The Bad About BMI
As mentioned above, the main problem with a Body Mass Index reading is that it doesn’t take into account the lean body mass. BMI often emphasizes the amount of mass a person has or doesn’t have. For example, an in-shape bodybuilder is often found to be obese because of their size, while a slender individual with little muscle mass might be seen as normal weight even when they are underweight or “skinny fat.”
For bodybuilders, athletes, and those with an apple shape—where the weight is carried predominately around the midsection—the waist circumference measurement is a more accurate indicator of health. Waists that measure larger than 40 inches in men and 35 inches in a woman could be a sign that the individual has too much visceral fat.
Visceral fat cushions internal organs, but too much raises your risk of conditions like Type 2 diabetes and heart disease. Subcutaneous fat is beneath the surface of the skin, the kind that you can pinch with skin calipers. Even if you’re slightly overweight, it’s better to have more subcutaneous fat, especially on the hips and thighs, than it is to have high amounts of visceral fat.
However, some people have thicker midsections solely because they have a lot of muscle.
The Ugly of BMI
Now, the problem with BMI that is most egregious is the fact that BMI doesn’t take into account where the weight comes from, so even the elderly who have high amounts of body fat and little muscle mass might have a normal BMI. This is why so many fitness and health professionals tend to scoff at BMI charts because you might be considered overweight, even when you’re covered in muscle and have very little fat. The ugliness ensues when people forget one very important thing: you, as a bodybuilder, might be called overweight by a BMI chart because of your mass, but it takes an unnatural (read: steroidal) amount of muscle to reach obesity.
However, this criticism is forgetting what the BMI was made to do. The Body Mass Index is extremely accurate when predicting obesity in children and adults. Research (1) has proven that, for those with a BMI reading that points to obesity, there’s a 95% chance for males and 99% chance for females that you’re truly obese.
The takeaway from all of this information is that, if you’re tracking body fat, working out, and eating optimally for fat loss and muscular gains, your BMI score should be normal. Use BMI like a snapshot into your overall health, helping you understand if you need to continue putting on weight, or if it would be a good idea to lose weight, especially around the middle. This insight can be the beginning. Where you take that BMI number from here is all up to you.
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References
(1) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2877506/
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