Your Body Fat Percentage: How It's Measured And Why It’s Useful
A body fat measurement can be a useful part of your fat-fighting toolbox, but it shouldn't be the only one you use. Here's how body fat is measured and the best ways to use that number!
I recently measured a woman's body fat because she didn't like the number her personal trainer had given her. Maybe you've been tempted to make a similar request. There isn't anything wrong with it, but it shows a misunderstanding about what a person's body fat percentage means and how it's measured. So let's clear it up.
Here's a basic rundown: A body fat test is an attempt to separate every pound of your body into one of two categories: your fat mass and everything else. What isn't fat mass is considered "lean body mass" which consists of your bones, muscles, hair, water, and miscellaneous stuff. So no, it's not just muscle!
This ratio can be deceiving in a number of ways. For instance small, slender people who don't weigh much may actually have a greater percentage of body fat than larger, more muscular people who weigh more. That's just one reason why your weight on the scale doesn't necessarily measure the level of your health.
Measuring Body Fat
There are many different methods for measuring body fat, but some are more accurate than others. Hydrostatic weighing and other high-tech machines are expensive and almost impossible for a layperson to access. There are also hand-held devices and scales which measure body fat, but these are often inaccurate. For our purposes, the easiest and most accurate choice is the caliper method.
The caliper method—which you can learn to do yourself—measures skin folds and then puts those measurements into a formula. The formula will then spit out an estimated body fat percentage. Those formulas can also determine your fat weight and lean mass weight. Depending on the type of formula you use, you'll grab skin folds of various areas of your body. It can be terribly difficult to pinch yourself and read the caliper at the same time. That's why I recommend getting a qualified professional to do your body fat measurement. If you don't have a pro at your disposal, grab a friend and learn how to measure each other's body fat together using this article as your guide.
For the general population, I recommend the Jackson and Pollock formula. This formula can be utilized in three-site , four-site, and seven-site tests. For people who carry more body fat than most of the population, I prefer the four-site Durnin and Womersley system. For lean bodybuilders, I use the nine-site Parillo equation. Although you're by no means limited to using these formulas, they seem to work the best and are the most widely used.
Each of these formulas is built upon fairly complex mathematical equations which take the sum of the caliper measurements and apply them to a constant. Unless you're really into math, how the formulas work doesn't really matter. What's important to remember is consistency. Choose a test, choose a formula, and stick with it!
Why? If you use a different formula, you can and usually will get a different result. If you use a different caliper, you can get a different result. If you measure seven points instead of three but use the same caliper and formula, you can get different results.
Your choice of formula or the quality of your calipers is much less important than getting consistent numbers. The data is valuable because it reflects a change in your progress, not because of the actual number. Whether your body fat is truly 8 percent or 10 percent doesn't actually matter at all. What matters is that you see progress.
Using What's Useful
What constitutes a "healthy" level of body fat depends a lot on your sex and your goals. If you're not worried about keeping your body fat low for aesthetic or performance goals, then it's perfectly OK to have the goal of keeping your body fat percentage anywhere below "obese" and above "essential fat levels."
|Obese: > 31%||Obese: > 25%|
|Acceptable: 25-31%||Acceptable: 18-25%|
|Fit: 21-24%||Fit: 14-17%|
|Athletic: 14-20%||Athletic: 6-13%|
|Essential fat levels: < 13%||Essential fat levels: < 2-5%|
To determine lean/fat mass
- Fat mass: Weight x body fat percentage
- Lean mass: Weight - (weight x body fat percentage)
Use that number to gauge progress, because the scale doesn't always tell the whole story. You might be losing weight or gaining weight, but where is that weight coming from? Muscle or fat?
From a planning perspective, having your body fat percentage measured can help you determine realistic goals. Knowing your ratio of fat mass to lean mass will make it easier to determine how many pounds of fat you can likely lose each week. For instance, if you have a goal to lose 15 pounds in three months, knowing what percentage of your body composition is actually fat can help you decide whether that goal is reasonable.
Changes in your fat and lean mass weight can also allow you to make smart decisions about your programming. For example, if you lose lean mass, it means your nutrition probably needs a second look or that you may be training way too much.
Keep your eye on the big picture
For most people, the ultimate goal is to have a better-looking, healthier body, so don't become obsessed with this or any measurement. It's OK to use it, if only to put a number to the cosmetic changes you see in the mirror, to notice how your clothes fit, or track the effectiveness of your nutrition and training.
Do you know what your body fat doesn't measure? Your health, your value as a person or as an athlete. These can't be measured with any number. Simply use this technique to gain one more level of insight. It can be a great tool to have in your arsenal.