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.

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