Safe to say, everything we know about body mass index or BMI isn’t entirely correct
One of the most widely used means to measure body fat is body mass index (BMI). Many people believe that if their BMI tells them they are overweight, then they are unhealthy. While BMI may be valid to a certain extent, people rely too much on it without fully understanding the method.
What is BMI?
BMI is measured by dividing a person’s weight (in kilograms) by the square of their height (in meters). Based on this calculation, people are divided into four categories: underweight for those with a BMI of less than 18.5, normal for those between 18.5 and 24.9, overweight for 25 to 25.9, and obese for anyone scoring 30 or higher.
What are its limitations?
BMI can be a health indicator to an extent, but it’s a broad measure that doesn’t take into account other factors such as muscle mass, bone density, and fat proportions. According to Medical News Today, it also doesn’t account for age and sex. Women can have more body fat than men of the same BMI, and older people can have more fat than younger people of the same BMI.
For sedentary individuals, BMI can more accurately represent their body fat percentage but for active athletes or those with frequent exercise habits, it may not be as accurate. Since muscle is more dense than fat, muscular people like bodybuilders and football players would likely have a BMI that says they’re overweight but actually have low fat levels.
Another limitation to using BMI as a health indicator is that it can’t distinguish the kinds of body fat. Visceral or belly fat has far more health risks than subcutaneous or “beneath the skin” body fat, which is about 80 percent of all body fat. But are there alternatives to BMI? Let’s take a closer look:
Body Adiposity Index (BAI)
Unlike BMI, BAI doesn’t measure weight; instead it estimates body fat by comparing the hip circumference to the height. Multiply a person’s height (in meters) by 1.5 then divide the product by the hip circumference (in centimeters). Lastly, subtract 18 from the quotient to get the BAI. Convert it into a percentage by multiplying it by 100, and that represents the body’s fat content. That said, studies have also argued that BAI may not also be recommended “in determining body fat percentage in adults” and it may be used as “an additional marker” in body fat assessment.
This method also uses hip circumference to whether someone is at greater risk of developing certain health conditions—though it isn’t an infallible method. To do it, measure the waist either at the smallest point or just above the belly button and divide it by the widest part of the hips. The result should be less than one for men and less than 0.85 for women.
Waist in itself can determine health because it helps give a rough estimate of a person’s belly fat. According to the National Heart Lung and Blood Institute, risks increase for women who have a circumference of over 35 inches and men over 40 inches.
There are pros and cons to the measurements given, but the point is that you should not base your entire fitness goals on rough computations. It can motivate, yes, but it’s not about counting numbers rather it’s about living a healthy lifestyle.