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Jason N: BF% Follow-Up

Jason: Just some follow-up. As you may remember, I use the Tanita-612 and the Omron Body Logic Pro to follow my body composition.(I use them both as sort of “double checks”, along with mutiple measurements, for greater accuracy). Just some things I wanted to follow-up on:

1)I tried dampening the bottoms of my feet for a while prior to measuring on the Tanita. There was no significant difference in my measurements over time.

2)The Omron shows less fluctuation, over a series of measurements, over time, BUT a)remember that it does not measure your weight and b)the Tanita takes your full body weight (unlike the hand held Body Logic). However, they are still consistently within 1-2 percentage points of each other.

3)I would like to echo something you have been trying to drive home, Jason: CONSISTENCY BREEDS GREATER ACCURACY WITH THE IMPEDENCE DEVICES! All in all, I’m very pleased with both devices.

Just a few notes; I just got the Tanita-626 a few weeks ago and am already starting to notice some things that might help give more consistant readings. If you’re taking measurements first thing in the morning, if you aren’t on a set schedule, you’re gonna get drastically inconsistant results. Try to go to sleep and wake up at the same time. (I notice differences of several %'s depending on whether I wake up at 6AM or 9AM for classes)Even more helpful would be to have your last meal at the same time each night before you go to sleep. These scales are incredibly sensitive to water weight fluctuations so keep in mind how hydrated you are before interpreting your reading.

Statement #1 - I also tried dampening my feet with no improvement. That is why I did not recommend this in my article.

Statement #2 - I have not used the Omron, but I do like the Tanita because it gives you both measurements. I'd rather have my second check method come from skinfold calipers, but I have greatly lowered the amount of times I use calipers because I've had such good success now with my Tanita TBF-551 scale. My measurements have varied no more than 1.5% in a week for 3 months now (usually less than 1% and I can predict if it will be high or low each time)

Statement #3 - Agree! Agree! Agree!

Other comments - Kingprotein brings up some good points about trying to measure at the same time. This may be impossible for some, but it should not really screw up your results too bad. Measuring at different times of the day, such as morning compared to evening compared to bed time WILL DEFINATELY screw up your results.

The fluctuations you see with bioimpedance are due to hydration differences, so expect to see them when you drink different quantitites of water or consume different amounts of carbohydrates. Here's 2 examples:

Example 1 - You drank much less water on Wednesday than normal including no water after 8pm and you go to bed at 11pm. Expect to wake up dehydrated on Thursday and see a low body weight and a higher % body fat. Water (73%), Protein, Mineral and Glycogen make up lean body mass and water makes up the greatest portion (I can add the other percentages later, just don't have them off the top of my head). Fluctutations in water don't change the amount of fat on your body, but it does change the ratio of fat to lean body mass so prepare accordingly.

Example #2 - You're doing a cyclical ketogenic diet. You're carb depleted M-F and carb load on Saturday. Expect Sunday morning to show a large increase in weight and a significant drop in %body fat. You likely added around 5lbs of glycogen and water (lean body mass) (each unit of glycogen needs 2.7 units of water for proper storage).

Bottom line - I recommend skinfold calipers to most people who are starting to measure their body composition not because I think that calipers are significantly better, but because bioimpedance requires a thorough understanding of the underlying components of body composition science and research to truly interpret the results. Here are my current recommendations for those using an impedance device:

Every morning (first thing after going to the bathroom) measure yourself in the nude or wearing minimal clothing. Drop the first measure and take 2-5 other measures until you see the same one at least twice and average the other 2-5 measures for your daily body comp number. You will have a lot of day to day variation so don't worry too much about day to day flux. Once you have 7 measurements (Mon-Sun), average them and that will become that week's body composition measurement. Compare weekly averages. DO NOT compare day to day flux or you will go nuts. I guarantee it. Stick with weekly averages and you will have a good experience.

If you guys liked what you heard, send TC an email. I submitted an article detailing my thoughts on practical body compostion measurement for the body builder. Questions on this topic are constantly arising and I think the article should handle most of anybody's basic questions. And if there are more detailed questions, you guys always know that you can find me right here on the forum.

Good luck and happy measurement!

i think i am a perfect example of Jason’s Example #2. i was doing a hypocaloric diet massive eating stle for the past 2 weeks. i was still taking in about 250g of carbs a day though with 3 protein/carb meals and 3 protein/fat meals a day. i started the diet at 170 and 12% according to the tanita and finished at around 163 and 11%. I just started my mag10 cycle today and upped my carbs to 600g a day and upped my total calories by 2000 a day. now the tanita reads 173 and 9%. that’s 10 pounds heavier and 2% less fat from one day to the next. hopefully the results will become more consistent throughout the rest of the week.

Nic - you are exactly right. That is a perfect example of what to expect with bioimpedance measurements. Bioimpedance is great because it can tell you exactly what kind of weight you are gaining. In your example, you just topped off depleted glycogen stores and added a bunch of water. Your fat mass did not change but your ratio of fat to lean did, thus your %body fat will change. Definately expect to see the numbers stabilize as you maintain this type of diet for a couple of days.

I’ve got one of the very, very early model Tanita scales. Its measurements are all over the shop and I no longer use it for BF readings. However, it works fine as an expensive set of scales.

I’m very confused, I have a tanita and have tested many of my clients on this machine. I take their bf reading on the scale then I do a skinfold, calliper check on 9 spots of the body. Everyone’s bodyfat I have done has been within 1~2% of the scale. When I do my own bf with the calipers I am about 6% which is pretty accurate because all me abs and intercoastalls are very detailed and visible. But, when I step on the Tanita scale, it says 17~18% BF. How can it be that off? All the other people I have checked were within 1~3% of the callipers.Why am I 11~12% off. I have been seriously training for 20 years, all the other people I tested have under 8 months of resistance training under their belts, I think that is whats causing the problems. Something is just not jiving, I just tested a person with 4 years training expierience and he was the same bf as me according to the Tanita scale, he is quite fat and I’m totally ripped and the freakn Tanita says we are the same, whats up with that? Why was there a warning on my scale that said “this scale is not accurate for professional bodybuilders” WHY? any thoughts???

First of all, you are a guy, so please get a new handle. Now, back to your question. What do your feet look like? If the skin is thick, dry or crackly, you may not be able to conduct a signal well throughout your body. You may want to swing by a store that sells the Omron analyzer and give that one a shot.

Another unlikely source of error is that you could be chronically and significantly dehydrated (this is the lame logic that the Tanita people have said about all bodybuilders and is why they give you that warning).

There are many many ways to measure body composition and some ust don’t work well with some people. I have seen fluctuations of 15+% in people between different methods like Hydrostatic weighing, bioimpedance and DXA. I have not seen such a drastic difference for someone who is as lean as you though. I don’t have a real good answer, so check your feet, try a different bioimpedance device and use skinfolds to monitor your body composition.

DOOCH, I experience the exact same problem! The scales put me at 165 pounds and 17-18%, whereas the calipers say I’m at 6-8%.

Jason: DOOCH’S problem brings up a point that I’ve been wondering about.

The Tanita-612 I have has an “athelete mode” that renders readings ON AVERAGE about 10 percentage points less than the “adult” readings (with the readings I’ve seen of various individuals).

Any idea exactly what occurs in the device when switching to the “athelete mode”? Stronger electrical pulse? Weaker? Other? (This may be something for DOOCH to consider).

However…I agree that all forms of measurement will not work for all people (an example that I’ve seen? Calipers do not work well if a person has a lot of loose skin from significant weight loss).

Mufasa - you bring up a very good point. In my opinion, anyone who is serious about bodybuilding should get a scale with the athlete setting.

This is more for psychological reasons than physiological because I think that both can show the changes that occur over time, but you always want to at least be close to the actual number.

As for changes in the way that the machine measures athletes versus sedentary folks, I don't think anything changes. What does change is the regression equation that takes into account your impedance, weight, height, sex, and athletic status and then converts that information into a %body fat.

It is extremely vital to realize that bioimpedance does not measure body fat directly. No method, except for ether extraction in a corpse can measure fat directly. Bioimpedance measures the body's impedance (voltage difference from starting point to ending point) and then integrates the impedance value, ht, wt, sex, etc. and spits out a %body fat. It has to rely on several assumptions about the body's compartments that may or may not be true in an individual's case.

It is obvious that sedentary people and athletes are very different, so to get a quality regression equation for the scale to work, they obviously had to do studies with both sedentary people and athletes to get the normative data.

If you are a hard training bodybuilder who takes careful note of what they eat, the athlete mode is the proper choice.

Got it!

So essentially the scales use the same voltages, etc, BUT by turning from “adult” to “athelete” mode, the computer in the scale utilizes a DIFFERENT calculation, that in turn allows it arrive at a different (perhaps more accurate) reading for the atheletic person.

Kewl stuff! Thanks!Mufasa

Glad I could be of service :slight_smile:

Zippy - I bumped this thread up for you. It covers the athlete/real person difference. If you have a specific question of which method you should use, I need to know how you are training, how long you have been training and your approximate visual % body fat or skinfold measures.


Thanks for the bump! What I got out of this is that the “athlete” setting is for people who’ve been training for a while, i.e. athletes. I have been training about a year and a half now, but only just started leg training (getting off the beach muscle work-out). I think that in a couple of months the “athlete” setting will be more applicable to me. I think that I fall somewhere inbetween the two right now. My plan is this -> Measure in another way as a sanity check. I am going to get some calipers and see what they say.

In my original post, someone (I forget who) mentioned to use the mirror as my “measure”. This is why I think I am closer to the “adult” setting :wink: Working on getting down, but I think that I am not as low as the “athlete” setting reflects (yet).

Thanks for the great information!!


Glad I could help you out. Have you seen my recommendations for using calipers? I’ve talked about them a lot in previous posts so let me know if you need some help. My suggestion is to pick up some slim guide or accu-measure calipers and use the male 3 site skinfold equation. Check out www.enforcergraphics.f2s.com/ bodyfat.htm for any easy online skinfold calculator. The recommendations at the site are good for placement and make sure to take several measures at each site.

first off, kudos to jason and mufasa. i myself have documented over 18 months worth of specifically timed two-a-day bf% measurements and can confirm that what jason and mufasa propose is absolutely true. i myself use my bodyfat monitor as more of a tool for tracking hydration levels and water partitioning in addition to the obvious bf%. although i have an interesting bit of info regarding the hand held omron model specifically, but holds true for all impedence monitors.

remember that electric current always follows the path of least resistence and depending on where you packed on your new muscle (ie upperbody vs. lowerbody) this muscle may or may not register on the monitor as muscle. it could very well register as fat. the data that i have collected suggests this is the case and a recent mag10 cycle proved this to me beyond a doubt.

i have always known that post workout bf%measurements always yield a lower bf% reading due to the water repartitioning that takes place during a massive pump inducing workout. more water and fluids in the muscle yields less resistence and lower readings. depending on which muscle group you just worked out you will get a different reading. to test this i took pre and post workout bf% measurements and noted the difference in the numbers. all pre/post numbers were different (post always being lower), but the most drastic difference was when i worked shoulders and traps. the post workout reading was a whopping 2% less than the pre workout reading. interestingly, the further away the muscle group was from the logical path of least resistence of the monitor the less difference there was between the two measurements.

if you think about the path of current travel for a handheld device it would be to go from one hand through your arm across your shoulders and traps and out your other arm. my readings suggest that the current does travel elsewhere in the body because other less influentially located muscle groups yielded a difference as well, but not as much. this makes me wonder about the timing of measurements not only in terms the time of day, but in relation to your workout schedule in general. we all experience the flattening (or de-volumization and dehydration) of muscles we worked out the day before and depending on which muscles they were will have a varying effect on your measurements. and as these muscles begin to recover, grow and re-volumize the measurements will vary as well. it seems to me that as long as the change in fat composition during this timeframe is significant enough it’s effect on the measurements could weigh in more heavily and could in essence override the effects of varying muscle volume. just a thought.

about my mag10 cycle. it appears that my “baseline” for bf% measurements has been adjusted due to a massive muscle gain in my glutes and hams. essentially after completing my mag10 cycle i am visually as lean as i was before (actually a bit leaner) but my weight is up 16 lbs, but because of the location of the gain (my legs) it registers that i have 10lbs more fat mass than i did when i started. so basically the monitor thinks i am fatter (13% post cycle vs. 7% pre cycle). that is a HUGE freakin’ difference. i believe this is directly related to the “path of least resistence” idea that i discussed above and because this extra mass is not close enough to the current’s path to be registered as muscle it is registered as fat instead. gotta love it, eh? kevo

Simply outstanding, Bro!

Yea…Jason really got me clued into how these devices work. The greatest revelation was that they DO NOT directly measure fat, but extrapolate fat weight from your total weight. Since the Omron has no “athelete” mode, your descrepency makes a LOT of sense. The Tanita, however, seems to take lean mass into account much more with it’s “athelete” mode.

Again…like you…the two devices together…along with consistent, serial measurements…have worked great for me.

This thread should explain most of my current thoughts on how to use a bioimpedance device.

Once again, let me know if you have any questions.

-Jason Norcross

Hope this helps.

Let me know if you have any questions.

-Jason Norcross