PDA

View Full Version : Body Fat Measurement


Barry Cooper
06-28-2003, 07:22 AM
I have been using a Tanita Scale with the Bioimpedance thing to measure bodyfat. It has consistently told me that I'm about 32%, which has always seemed pretty high to me.

The other day I was talking with a guy in the Navy who said they just deduct your neck circumference from the measurement of the fattest part of your gut, and the resulting number is your rough bodyfat. Using that system I'm about 22% bodyfat.

I'm got modest love handles, but I also don't look chubby, just big. I'm pretty strong. If I tense my stomach you can see clearly defined muscles.

My question is this: has anyone compared a Tanita to an actual immersion test? Secondly, what methods are people using to test bodyfat? Are calipers accurate in general? Any thoughts/views based on your experience would be appreciated.

Barry Cooper
07-01-2003, 07:22 AM
I know I'm a fat boy, but I'm doing every rep and set of every workout. It's taking me up to three times as long as the top guys, but I'm doing it.

Based on other posts, people are measuring their bodyfat. How are you doing it?

David Wood
07-01-2003, 09:59 AM
Barry:

Sorry you've had no replies here . . . but generally, when you get nothing, it means that no one really knows enough to tell you with confidence.

My limited understanding is that underwater weighing (immersion) is still the "gold standard" of testing (although it's still quite imperfect . . . I think the only TRULY accurate measurements are done during an autopsy, so let's leave those aside for the moment).

Skin-fold caliper methods are also supposed to be very good (there are various formulas on the web, and the calipers themselves are pretty cheap). I've seen some reports that complained unless the person taking the measurements was VERY well trained, the results would be garbage . . . I have a hard time seeing this argument.

What you're mostly looking for in any method you use is consistency and repeatability . . . you want to know that when you take a measurement on yourself, the values it gives you reflect a real change in your fat level . . . not just random fluctuation within the measurement technology. For skinfold testing methods, this means getting exactly the same site(s) on your body every time . . . which basically means using very good (repeatable) "landmarks" to find the site. The numbers you get may (or may not) be perfectly comparable to what others report, but getting very involved in those comparisons is a waste of time under any conditions (even if all reported BF% were perfectly accurate). What matters is whether or not you are showing any improvement over time (which I guarantee you will if you stay with CrossFit, as you describe).

Actually, the single best test I know of is to stand naked in front a full-length mirror, or, better yet, one of those angled 3-way mirrors that will also show you your backside. An honest appraisal of what you see there, and whether it's getting better or worse, probably tells you most or all of you need to know about your body fat level. If you need to, take pictures (digital cameras don't need to be "developed" anywhere but your own computer) to make a record of your progress.

My understanding is that the "repeatability" of methods (like the Tanita scale) that depend on electrical impedance is not good . . . minor variations in your state of hydration (fully hyrdrated vs. dry) may affect the total impedance level your body tissues, and thus the readings.

One fairly simple way to test it is to take repeated readings every couple of hours over a couple of consecutive days. If the reported BF% varies (and I think it will), then you can be reasonably confident that the method suffers from poor repeatability . . . because you can be pretty sure that you aren't gaining or losing significant amounts of body fat or muscle in just two days. If it comes back with the pretty much the same reading each time, you can have a bit more dependence on it. Even if it does vary, you will at least have some idea of the underlying variability of the method, so you will know how big of a change is needed in order to be "real" when it reports it.

If you are doing every rep and set of every workout, and not eating everything in sight, I guarantee you will see changes.

Dave

Barry Cooper
07-01-2003, 10:30 AM
Thanks. I think I'm going to ignore the Tanita. I've seen 4 point swings in a day. They claim it's +/- 1%, but I just can't see that. That's a bummer b/c it will be hard to get consistent feedback, but better than incorrect feedback.

I've been doing this about 2 weeks, and I think I'm getting a bit trimmer, although my muscles are actually getting a bit bigger--especially my arms--since I only did very low reps before and now I'm mixing it up a bit more.