Discover your ideal body fat range. Then, explore various methods for measuring body fat, assessing the strengths and weaknesses of each. These include the Bod Pod, skinfold pinching, and Bioelectrical Impedance Analysis.
Determining Your Ideal Body Fat Range
What is the ideal amount of body fat? Typically, body fat levels are broken into optimal health and optimal fitness.
Generally, health refers to the optimal level for reduced risk of disease, and fitness takes it a step further. We should all strive for at least optimal health.
For women, optimal health is a body fat range of 18%–30% and optimal fitness is 16%–25%. For men, optimal health is 10%–25% and optimal fitness is 12%–18%.
Consider your fitness goals to determine which range you should fall into. Then, determine your current body composition.
Many methods exist to measure body composition. Keep in mind, though, that most methods have an error margin of 1%–4%.
For most of these tests, you can either ask your local gym personnel to administer them, or search for a human performance or exercise science laboratory at a local college.
Advanced Methods for Measuring Body Fat
Some of the more expensive and laboratory-based methods include:
- Hydrostatic or underwater weighing
This method involves getting into a large tub of water, going under, and fully exhaling. This is definitely uncomfortable.
But with underwater weighing, it’s important to expel as much air from the lungs as possible to get an accurate measurement. When you go underwater, you displace water.
“By weighing you both underwater and on dry land, we can calculate your body volume and density,” said Dr. Michael Ormsbee, Associate Professor in the Department of Nutrition, Food, and Exercise Sciences at Florida State University.
Because muscle is more dense than fat, those with more muscle mass will have a greater body density, and those with more fat will have less body density. Ultimately, this technique is a great tool, but it can be difficult to get a truly accurate measurement.
- Air-Displacement Plethysmography, or the Bod Pod
The Bod Pod relies on Boyle’s law: at a constant temperature, volume and pressure are inversely related. As with with hydrostatic weighing, body volume is measured and then body density and body fat are estimated using standard calculations.
- Dual-Energy X-Ray Absorptiometry (DEXA)
This method is most often used in hospitals or research laboratories. Here, you lie on a flat table as a scanning arm crosses above you to systematically image your body. Using a very low-dose X-ray, about the amount you would get from a transatlantic flight, the DEXA calculates areas with more or less density, including your fat, muscle, and bone tissues.
More Common Techniques
- Skinfold measurements using skinfold pinches
This method of assessing body composition is practical and widely used. A caliper, or a plastic or metal pincher, is used to pinch the fat underneath your skin at specific sites on your body.
Many times this method includes just three different sites. For women, this would be the back of your arm, your thigh, and your suprailium, which is just above your hip on the outside of your body. For men, the pinches are taken at your chest, your abdomen, and your thigh.
Ultimately, the percent body fat is calculated from your estimated body density using standard equations. Unfortunately, there may be considerable error depending on the type of caliper and the experience of the technician.
- Bioelectrical Impedance Analysis (BIA) using an electrical current
This is the most commonly used body composition analysis tool by gyms and clinics. Models include handheld devices that you hold onto like a steering wheel, floor models that you stand on like a scale, and high-grade BIAs where you lie on your back with small electrodes attached to your hands and feet.
“With bioelectric impedance analysis technology, we use electricity to assess body composition,” Ormsbee said.
Because much of your body is comprised of water, and muscle mass is particularly concentrated with water, an electrical current can pass through quite easily.
On the other hand, fat contains little water and will blunt the electrical current, slowing down the signal. The BIA uses a very low-level electrical current—you can’t even feel it—and usually just two points of contact. Within the handheld model, this would run from your left hand to your right hand, and based on the relative amounts of fat and muscle you have, the BIA will calculate the speed of the current and ultimately estimate fat-free mass and fat mass.
Because this tool relies on total body water, naturally how much water you’ve had to drink will influence the results of this measurement.
In practice, the BIA tends to work well for most people to accurately gauge body fat levels, but it also may give very lean people a higher body fat measurement, or very obese people a lower value than anticipated.
Nevertheless, this tool can be used to track body fat levels over time, as long as you’re consistent. Eating and drinking habits as well as activity level should be similar before testing.
Now, you know how to measure your body composition. But remember—all of these methods can only estimate your body fat percentage.
Dr. Michael Ormsbee is an Associate Professor in the Department of Nutrition, Food, and Exercise Sciences and Interim Director of the Institute of Sports Sciences and Medicine in the College of Human Sciences at Florida State University. He received his M.S. in Exercise Physiology from South Dakota State University and his Ph.D. in Bioenergetics from East Carolina University.