The Weight/Body Fat Conundrum

Body weight doesn’t matter, body fat does. Here’s an analogy. Think back to your middle school Earth Science class. Remember when you had to weigh different rocks, and it was shocking to find a small rock that was much heavier than it looked, even heavier than larger rocks? What was your teacher’s explanation? If you don’t recall, here it is: the small rock was more dense than the others; in other words, it had a tightly-compacted atomic structure. Density impacts weight. The more dense something is, the more it weighs. The same is true for muscle versus fat. Muscle is dense and compact. Fat is less dense, but occupies more space.

As you lose body fat, you can retain or develop muscle simultaneously. Given this reality, your weight can ultimately change minorly: increase while your body fat percentage decreases, or your weight can even stay the same.

In a society that places emphasis on the scale, teaching my clients the basic science of density versus volume was a big challenge. It’s simple, really. Your total body weight consists of your blood, bones, muscle, body fat, whatever you just ate — or didn’t eat — waste, and so on. This can, of course, fluctuate — and does frequently. Conversely, your body fat percentage is, well, your body fat percentage. Its number reveals more about the state of your health than the fact that you have blood and bones that weigh something. Body fat percentage also takes time to change, and the handy thing is, it’s a measure of what those scale-obsessed people really want to know: how much of their weight is fat. The image below demonstrates why this is so important.

Now that you’ve learned the difference between total body weight and body fat percentage, it should really be a no-brainer to be more concerned with body fat percentage than how much your body waste and all that fun stuff weighs at any given time. Still, many people (women especially) obsess over the scale. Please, take the logical route. Get your body fat percentage checked at a local gym for free, or buy a body fat analyzer or calipers, and simply check what you really care about: your body fat percentage. Below is a chart of body fat percentages for women and men recommended by the American Council on Exercise.

BONUS: Once you find out your body fat percentage, subtract it from your total body weight. From there, you’ll have your body-fat-to-lean-body-mass ratio. That information can help you determine more accurate caloric needs than calculations based on ever-fluctuating body weight. To get you started, input your body fat percentage, activity level, weight, and other metrics into our calorie calculator to learn your caloric needs based on the goal of fat loss, muscle gain, or maintenance.

Try Our Calorie Calculator

Our calculator utilizes the Katch-McArdle formula, which factors your lean body mass and activity level to determine your caloric needs. Lean body mass is obtained by subtracting your body fat percentage from your weight, thus, leaving working mass (muscle) as a primary determinant of your caloric needs, along with your activity level.

Article initially published on December 9, 2016 - Updated and republished on May 24, 2018

LLAFIT Senior Writer/Editor

As an athlete for over 21 years and a broke single mom for most of that time, I created brokesinglemomfitness.com, now LLAFIT.com, to aid anyone who believes the road to fitness requires a lot of cash or time. In reality, the way to fitness is paved with knowledge and firm principles; teaching readers how to master both is the goal of this site. LLAFIT – Lifelong Applied Fitness