Your Body Composition

Your body consists of skin, organs, muscle, bones, water, and fat. But most people, when they think about body composition, limit their consideration to two broad constituents: that which is fat and that which is not fat. This is only partly because of our beauty obsessed culture. The truth is that your ability to control the proportions of most of these things is pretty limited. You can’t deliberately subtract bone mass, you can’t ordinarily grow new organs. But you can readily lose fat and grow new muscle mass. We’ve talked before about you do this with diet and exercise.

Healthy Body Fat Percentage

According to Winchester Hospital (of Beth Israel Lahey Health), the percentage of healthy body fat varies between genders and changes with age. For women, it is 21%-32% (ages 20-39), 23%-33% (ages 40-59), or 24%-35% (ages 60-79). For men it is 8%-19% (ages 20-39), 11%-21% (ages 40-59), or 13%-24% (ages 60-79).

Medical News Today offers charts that break down the ranges even more precisely. Their chart gives values for “excellent,” “good,” “fair,” “poor,” and “dangerously high.” But it also gives one for “dangerously low.” This suggests that too little body fat, while it might make your photo suitable for a magazine cover, is unhealthy. Specifically, it can affect fertility, immunity, heart health, and something I would call “disease endurance.” At the other end, too much body fat sets you up for diabetes and cardiovascular problems. 

Measuring Body Fat

How do you even measure your body fat? There are a handful of ways to do this, from skinfold calipers to water displacement. Some of the measuring techniques require expensive equipment or a highly trained measurer, or both. The most accessible method is bioelectrical impedance. This is what you find in those bathroom scales that measure body fat at home.

When you use a body fat scale, the device passes a weak electrical current through your body via the soles of your feet. The current is so weak that you can’t feel it. But the scale can measure it, and when it measures how much of the current comes back compared to what it sent out, it knows how much resistance (impedance) your body offers. Your muscles hold most of the water in your body. Current passes through water faster than it passes through fat. These principles allow the scale to estimate your body fat. You can see right away that it’s easy to cheat the scale by drinking a lot of water right before using it. Your reading will also be inaccurate if you measure on a full stomach, or if you exercise (and dehydrate) right before using the scale.

Tracking Body Composition

Because bioelectrical impedance can be fooled by so many variables, body fat experts prefer more expensive techniques like water displacement or dual x-ray absorptiometry (DEXA) scan. I would suggest, however, that bioelectrical impedance measurement can be very useful for maintaining your health. Just make sure you aren’t doing anything to defeat the measurement when you take it. It’s a good idea, for example, to take it at the same time of day every time you do it. If you take it regularly, you can use it as a relative measurement. It doesn’t really matter how accurate it might be if you’re only trying to see whether it’s going up or down. What matters for tracking is consistency, and since it’s an electromechanical device, it will be consistent.

If you have reason to believe your body fat might be outside the healthy range, my advice is to get a body fat scale. Then line up one of the expensive measurements, such as DEXA scan or water displacement, and get the most accurate reading you can. Go home and take the best measurement you can on your body fat scale (no over-hydrating beforehand, empty stomach, etc.). Use the expensive measurement to calibrate your at-home measurement.

Just so you know, here at Peak we offer the InBody body composition scan as part of our nutrition planning service. And that might be the most reliable way to manage your body composition.

Photo: One of Peak’s helpers, Floyd Kemske (known to his Withings body fat scale as “FLO”), clocks in at 17.6% body fat.