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BMI vs Body Composition

Everyone would like to have a great BMI (Body Mass Index), but what if I told you that a good Body Composition will not only make you healthier, but look better, too?

Let's talk (briefly) about what these two things are, and then we'll discuss why Body Composition is better for you.

Measuring your weight at the scale

Body Mass Index (BMI)

According to the CDC (Centers for Disease Control and Prevention), the American Heart Association, and the NIH (National Heart, Lung, and Blood Institute) Body Mass Index attempts to guess whether you have too much fat in your body based on your height and your weight. You literally divide your weight (in kilograms) by your height (in meters); the resulting number is supposed to tell you if you are "fat" - meaning, that you have too high of a content of fat in your body.

The problem with this measurement is that it does not take in to account your age, your gender, your muscle mass, or anything else which might affect a judgement of your fitness level. It is a gross estimation (grosstimation?) of your fitness based on two numbers, and nothing else. It's actually an attempt to gauge your Body Composition based on far too little information.

Body Composition

Body Composition is a measurement of your body's components. It might include fat mass, muscle mass, mineral mass, bone mass, water mass, organ mass, and fat location. Two two most commonly understood and useful statistics are fat mass (fat%) and muscle mass (muscle%).

In general, the higher your body's muscle% and lower your body's fat%, the more healthy you are. "Weight" is merely what you get when you add up your body's different components.

Sources:,,, Cooper Institue.

Sean's Body Composition

Example (non-hypothetical) Body Measurements

Let's pretend, for a moment, that (like me 3 months ago) you are a 47 year old male with 52.3 pounds of fat and 62.28 pounds of muscle, which adds up to 114.58 pounds, or 73.02 pounds less than my total weight of 187.6. That means that 73 pounds of my body are organs, bone, and water.

After three months of working out and good nutrition, the fat weight changed to 40.1 pounds (12.2 pounds lost), muscle to 65.05 (2.77 pounds gained). My weight changed to 178.4, so the difference between total weight and (muscle + fat) is 73.25. We now know what my body is composed of and can hopefully agree that I was healthier after those 3 months of working out and eating right than before. But did it really have to do with the "weight" that I lost?

In my case, yes, because not only did my muscle% not go down, but my muscle MASS went up. Losing 9.2 pounds of "total" weight could mean a lot of different things. In my case, it means that I lost over 12 pounds of fat! It could have meant that I lost 6.5 pounds of fat and 2.7 pounds of muscle.

Which do you think is more healthy - losing 12 pounds of fat and gaining 2.7 pounds of muscle, or losing 6.5 pounds of fat AND LOSING 2.7 pounds of muscle? (The answer is: Losing Fat and Gaining Muscle, NOT Losing Fat and Losing Muscle)

How Do I Find My Body Composition?

I figured out my body composition using an Omron Scale, but what if you don't have access to an electronic fat scanner like this?

Read my article on How to Measure Your Body Composition for several options on how to measure yours- be sure to continue reading this article when you're done with that one!

How To Change the Numbers

The water weight will vary by several pounds throughout each day and from day to day. Bone weight increases slightly as your fitness level increases, and decreases as you age or your fitness level decreases. Organs change depending on your health and fitness levels.

The two numbers that you can do something about, directly, are fat mass and muscle mass, so let's focus on what you can do to change those. Our goals: attain a healthy level of fat and a healthy level of muscle. Many people say they want to "lose weight," but really mean that they want to "get fit," which may involve gaining or losing muscle as well as losing (or gaining) fat, depending on where they're at now. See my article on Losing Weight vs. Getting Fit for more information.

What are the healthy numbers?

[[ Article Coming Soon ]]

Why Lose Fat

Everyone knows that if your fat content is too high that you want to lose fat, but they may not know the important health reasons why you want to lose fat. See my article on the important reasons why you want to lose fat. [Article Coming Soon]

How to Lose Fat

Now that you've learned why you want to lose fat, let's talk about how to lose fat effectively, and dispel some myths about fat loss. [Article Coming Soon]

Why Build Muscle

Unless you already work out with resistance (meaning working out with weights, bands, or body weight against gravity) you probably need to build more muscle. In this next article, I talk about why it's important to build muscle, no matter your age or gender! [Article Coming Soon]

How to Build Muscle

Now that we've talked about why building muscle mass is important, let's talk about how to build it.

Change YOUR Body Composition

Are you ready to get started changing your Body Composition? I'm here to help!

Sign up with Sean Arenas as your Fitness Coach - Welcome to the Arena!

#BMI #BodyComposition #Health #Fitness

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