In my opinion, the best method is still hydrostatic weighing because it is safer than a DEXA (Dual-energy X-ray absorption) scan, but both hydrostatic weighing the DEXA scan are fairly comparable to each other as far as providing the closest estimate of true body fat. There is also something called the Bod Pod. This device is a chamber that you get into that measures the overall air displacement of your body. I don’t know how it works exactly, but it’s supposed to be able to better account for hydration, the volume of air in your lungs, and other extraneous factors that often affect body fat analysis. Any of the above three techniques would yield the best results when measuring body fat. It’s not often that you see fitness centers with these facilities, however. Even then, you would need some certified medical professionals to conduct the tests and give clients directions on how to control for certain factors (like hydration).
For fitness professionals today, the two best methods out there in my opinion are skinfold calipers and Bioelectrical Impedence Analysis (BIA). I tend to err on the side of BIA because it’s more comfortable for the client. Even though it’s not as accurate as I would like it to be, I think it gives an accurate representation of body fat changes over time. This method can vary up to 5 percent give or take. It’s all dependent on how much water is in the body, ultimately. It’s hard to control for that. For women, the menstrual cycle can affect this measurement.
Skinfold calipers are great if you know what you’re doing. The problem is that a lot of people don’t use them correctly, and you might as well be throwing darts at a dart board. I, personally, find it very difficult to separate the fatty layers from the muscle underneath when pinching. Not only that, I’m always worried about my fingers slipping and pinching the client, which isn’t good for our relationship when I’m doing the initial assessment. So, call me inept, but I prefer BIA. Yes, there is a wide range of variability, however I view it as having less variability than if I were to inaccurately separate the fatty layer from the muscle underneath. I also see it as less invasive for the client. The BIA can be done quickly. This means that we can take measurements over a week (in a perfect world, at the same time of day) and average those measurements to get a more accurate assessment of body fat. That’s if we’re really interested in body fat. My experience is that body fat is less of a concern than are body image, strength, and functional movement. As long as body fat falls within an acceptable range for health give or take 5 percent, I think body fat shouldn’t be the focus of a training program.
Joanne is right skinfold calipers should be pretty accurate with the four spot measurement or 3 spot measurement for clients with lower body fat. Decent calipers are $15 to $200+ and usually come with a chart for the measurements or an alternative is electric impedance measurement with a specially designed body fat measuring scale. I use the cheap slimline calipers but I’d like to get one that is smaller and more comfortable