A Conversation About Body Fat% Testing » Oklahoma Sports & Fitness Athlete Blog | Running | Triathlon | Cycling | Fitness | Martial Arts | Powered by Oklahoma Sports & Fitness Magazine

Apr 022015

Have you ever thought to yourself, “I need to get in better shape!” I know I have.

In fact, I would bet that thousands, if not millions of people think this exact same thing every day. The thing with most people is — that’s where it stops. They might say it a thousand times during their lifetime, but never act on it. Why is that? Why haven’t they acted on that thought? Maybe it’s because they don’t know where to start.

I have a possible solution – a starting point: body fat% testing.  Body fat% testing is an essential first step in the process of “getting in better shape”.

Body fat% test? Umm, that sounds scary, what is it?

First off, let me shorten that term. From here on out “body fat% testing” will be known as BF%T, which should make it a little more manageable. Secondly, BF%T is not scary at all. It is simply a test to determine how much of your total body weight is fat. Pretty basic, right?

Sure, but why would I want to test my BF%?

There are many reasons why you want to have a BF%T. Not only does it indicate how much of your weight is fat, but, depending on the test, it can also show you how much of your weight is muscle and water. Additionally, it is an important factor in the goal setting process. You see, in order to find out where you want to end up, you have to determine where you are starting. Think of the BF%T as a first step in the quest to accomplish your goal of “getting in shape!”

That makes sense. How do you test BF%?

There are many ways to test BF%, but I will address just two of the most common methods found in fitness centers: skinfold measurements and bioelectrical impedance. Let’s take a look at each of them.

Skinfold Measurement

Skinfold measuring consists of measuring folds of the skin (imagine that) at different sites on the body using an instrument downloadcalled skinfold calipers. The tests vary from measuring as few as three different skinfolds up to as many as seven. Now, I know
what you are thinking – what if I don’t have any folds in my skin? Easy, skinfolds are created by pinching the skin and measuring the thickness of the fold. The numbers are entered into an equation which calculates your estimated BF%.

This test usually takes about 5 minutes and will estimate how much of your weight is fat mass and fat free mass. Skinfold testing can overpredict or underpredict BF% by as much 10% and 15%, respectively; however, one study reports that the error rate is as low as 3-5% when measuring over a long time period (3 to 6 months) (Krieger). Much of the inaccuracies are due to tester error, meaning the person administering the test is not doing it correctly. Skinfold calipers are widely available which makes testing much more affordable. In fact, many fitness centers will do it for free making skinfold measuring a fairly accurate (long term) and economical method to test BF%. (image)

Bioelectrical Impedance Analysis (BIA)

The other method is known as bioelectrical impedance analysis, or simply as BIA. Of the methods discussed thus far, BIA is probably the easiest method of testing BF%. Many people even have scales that will test BF% using this method.inbody-230-medicion

BIA estimates BF% by sending a small electrical impulse through the body. The scale analyzes how much the tissues of the body impede (resist) the impulse, hence the term bioelectrical impedance. The impulse travels through all tissues of the body and some tissues impede the impulse more than others. For instance, tissues that are more hydrated would provide less electrical resistance than tissues that are less hydrated (fat). The scale would then analyze the data and estimate your BF%. (image)

One of the neat points about BIA is that it will tell you how much of your weight is fat mass, fat free mass, and water. The test only takes about 30 seconds, but has an error rate as high as 8% (Krieger). Essentially, this means that you could have lost 8% BF, but BIA might not even show a loss. Additionally, BIA is very sensitive to water. For example, if you were to test your BF using BIA right now, then drink a gallon of water (about 8 lbs) your BF% would actually be lower because the influx of water creates less resistance to the electrical impulse. That being said, if BIA is your chosen method, it is important to be as consistent as possible with respect to the timing of your test. BIA can be done at most fitness centers and is typically free. However, some fitness centers have more sophisticated BIA machines and might charge up to $30 per test.

Okay…that was confusing, so which one do you recommend?

Great question! Obviously, each method has some advantages and disadvantages. Each of them considered, I recommend BIA over skinfold measurement – with a caveat. Understand that BIA is very sensitive to external factors such as when you ate, when you worked out, and how well you are hydrated. As a result, it is very important to be as consistent as possible with BIA. I have my clients test at the same time on the same day of the week as previous tests. This allows me to track trends with some level of consistency.

Got it. When should I have my BF% tested?

At the very beginning of your fitness journey! Testing your BF% in the very beginning will give you some goals on which to focus. With my clients we set a goal to increase fat free mass (muscle tissue and water), decrease fat-mass, and decrease overall weight (for weight loss clients, anyway). We would not be able to set these goals if we only focused on total body weight.

I can do that! How often should I retest?

Because the error rate of BIA is as high as 8%, it would probably be best if you retested every three months. You can certainly retest more frequently, but remember that these tests are most accurate over a long time frame. I retest my clients every couple of weeks, but I don’t put too much thought into the biweekly tests. It’s similar weighing yourself every day. Your weight will fluctuate a great deal on a day-to-day basis, but your weekly weigh-in is a little more indicative of actual fat loss. The same goes for BIA. Don’t worry too much about a reading with only a couple of weeks in between, but do pay attention to the readings with a couple months between them.

Awesome! What if I have questions in the future?

I love questions. If you have any please leave them in the comments section!

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