Why Your “Body Fat” Measurements Are Inaccurate

As a personal trainer, I need a way to track my clients’ progress so we can continue to find ways to improve their results. A key indicator of how you are doing with your exercise, nutrition and diet plan is your level of body fat. The distribution of body fat in different parts of your body can also be an indicator of your hormonal and health status, as well as indicators of risk factors for certain diseases. These are the various methods of measuring body fat and how good/bad/accurate/practical they are.

In increasing order of precision…

looking into his eyes
Just use your eyes to measure. A person who is an experienced trainer or personal trainer can generally tell her body fat percentage simply by looking at her body from different angles. This is the most basic and simple method of measuring body fat. However, it is easily affected by water retention, menstrual periods, room lighting, and time of day. So this is not a recommended method.

bioimpedance measurements
This method passes a small electrical current through your body and measures how easily it passes. The idea is that muscle is mostly water and conducts electricity and fat doesn’t. So the more muscular and less fat you are, the better the current will pass. The problem with this is that these machines are often at your feet or in your hand. Since electricity takes the shortest path, it only measures part of your body, if it is at your feet, only the lower part of your body is measured, if it is in your hands, only the upper part of the torso is measured.

Waist to hip ratio charts
These charts aren’t too bad but require skill and consistency in measurement and the charts are made from a generalization of people who are not generally in an athletic population so if you are lean/strong/muscular/athletic the readings will be evil.

Skinfold Calipers/Skinfold Laser Gun 1-Site, 3-Site, 5-Site, 7-Site, or 12-Site Method
This is the way most professionals take measurements. The more skilled the practitioner or personal trainer is, the more sites they will use because they will know the value of multiple readings and what they represent.

We exclusively use 12 sites in the gym that I own because it can be used for what’s called biosignature modulation, a method of analyzing hormones and health status devised by Olympic trainer Charles Poliquin. As the number of sites increases, so does the accuracy and information that can be collected. Bio-Signature Modulation can help people whose hormones are out of optimal range so they can improve their health and get better results from their training programs.

The downside of caliper measurements is that you need a trained professional or personal trainer to consistently make an accurate measurement. A good practitioner can make thousands of measurements per year, making his skill invaluable.

underwater weighing
In this method, you will sit in a capsule that is almost completely filled with water. Using the volume of water displaced by your body and the weight of your body, your density can be calculated. From there we can determine how much fat you have because fat has a different density than muscle. An example of a piece of underwater weighing equipment is the “bod pod”. This method is accurate, but the equipment is expensive and will likely only be available to professional sports teams or other large organizations.

DEXA (dual energy X-ray absorptiometry) scanners
This is a full body X-ray that is more accurate than regular X-rays. It can also show where fat is distributed on your body. This is a very accurate measurement but will cost a few hundred dollars per measurement. And just like with the bod pod, it will only be available at high-end professional teams or medical facilities.

Here we go! All common fat measurement methods. For normal people, a good personal trainer or fitness instructor who uses and knows how to interpret a 12-site fat measurement and how it relates to your current health should be good enough.