Why BMI isn’t the best measurement of fat

By Ea Francisco

One of the most widely used means to measure fat is BMI or body mass index. People believed that if their BMI tells them they are overweight, then they are unhealthy. While BMI can be valid to an extent, people rely too much on it without fully understanding the method. 

What is it?

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. 

Limitations

BMI can be a health indicator to an extent, but it’s a broad measurement that doesn’t take into account muscle mass, bone density, and fat proportions. According to Medical News Today, it also doesn’t account for age and sex. There’s the tendency that 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 has more density 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 for health measurement is that it can’t tell the kind 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. There are other better methods to measure fat like these three alternatives:

Body Adiposity Index (BAI)

Unlike BMI, BAI doesn’t count weight, but 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.

Photo from Pixabay
Waist-to-hip Ratio

This method also uses hip circumference. 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 Circumference

Actually, 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 are increased for women who have a circumference of over 35 inches and men who have over 40 inches.

Experts and other institutions can provide a better reading with their special equipment. There are pros and cons to all of the measurements given, but the point is that one should not base their entire fitness goals on rough computations like these. It can help as motivation, but it’s not about counting numbers rather living a healthy lifestyle.