7 Reasons You Can't Always Trust Your BMI ...
Your BMI, or Body Mass Index, tells you many things. It measures your height against your weight, it teaches you a great mathematical equation, and it tells you if you're fat or skinny … but not really. If you have trouble understanding your BMI and what it means, you're not alone. It reveals your body fat, yes, and there's a scale to follow, but what does that mean? There's an equation to measure your BMI – (weight / height in inches^2) x 703 -- but what does it tell you? To fully understand what your BMI means for you, just keep reading!
1. Muscle Weighs More than Fat
Let's start off with an example: there's a purely hypothetical girl who is 5'6” tall, 142 pounds, and quite fit. Remember two things: the ideal BMI falls within the 18.5-24.9 range and her BMI – (142 / 66^2) x 703 – is 22.3. Based on her BMI, she's very close to being classified as overweight, which ranges between 25-29.9. Any lower than 18.5 and your BMI marks you as underweight; if it's over 30, you're considered obese. The problem is that muscle really does weigh more than fat, so although this hypothetical girl is close to the end of the “healthy” spectrum, she's also active and, thus, muscular. However, the BMI calculation doesn't consider muscle or its weight. It doesn't measure muscle so it lacks very important information.