There are a few different products and methods for measuring body composition (I’m not sure if you are asking for a comparison within different products to use, or within the same products to know which brands are better).
You can use skin fold calipers (take a little more training, but tend to be more on the accurate side depending on the testing skills of the trainer), hand-held bio electrical impedance machines (easy to use), body circumference via a tape measure (easy to use), and hydrostatic weighing in water (one of the most accurate measures). There is also a newer method for analyzing body composition using a DEXA scan that is supposed to be very accurate as well.
As long as you are using the same product to take retests, you can get a basic picture of body composition trends.
I hope I’ve helped to answer your question.
There are many different methods to measure BF as Christine mentioned. The underwater method is the most accurate of all but not the most practical since you have to go to a location that offers it. I have been using calipers for 25 years now and even though it has a 3% + or – error it’s the cheapest and most practical (for me at least). I’m sure newer trainers like to use the hand-bio electrical impedance machines, but those are not the most accurate either (especially for the amount of $ you have to spend).
There are so many body composition products on the market, are you looking for something practical or more a product that has the least amount of error as possible?
If looking for the “gold standard”, it is my understanding that DEXA which stands for dual energy x-ray absorptiometry is the gold standard and gives you bone mineral density readings also. Is it practical, not really unfortunately. Depending where you live, you can bet at the minimum price it will cost $100. There are other tools such as Bod Pod and the dunking tanks.
Something more practical is using calipers if you get really good at them, using BIA but understanding the variables that affect readings, and being consistent with measurements in my opinion. I’m a big fan of the “how my clothes fit” method especially if the client does not want to be measured or does not want to pay for such things.
Thanks Pedro. I agree with you about the “how my clothes fit” and also “how I feel”. I don’t always take the bf%, only if it’s necessary and my client really needs to know. DEXA has gotten some great reviews, but like you said it’s not the most practical way to measure BF%. Recently I had a couple of clients who did the Bod Pod method and I have to say that it’s not the most accurate tool.