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Fancy new scales - Bone density? Muscle Percentage?

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I tried my friend's fancy new scales and they gave me the following readings:

124.2lbs (i'm 5' 5 1/2")

fat percentage - 19.7%

water percentage - 59%

muscle percentage - 38.8%

bone density - 4.8

i know the body fat and water are good readings but i'm not sure about the muscle and bone density ones. are they good or not? is there a range? i had a quick google but couldn't really find anything very helpful. i've been doing a mix of cardio, weights and yoga so i'd like to know how that is affecting my body. i'm pretty much at the 'maintaining' stage of weightloss so looking now to improve my fitness and strength. any help?

Edited Dec 12 2013 11:28 by coach_k
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The number is meaningless unless you look at the scale's instruction book. It should tell you what their parameters are and on how they get to their numbers.

yes, that's what i thought but the book gave no indication of ranges/values for muscle percentage or bone density. it is a 'salter' scale as well which is, i think, a really good make. strange.

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Hi, did you ever find the ranges/values for muscle percentage or bone density? I looked in my Weight Watchers bathroom scale book, and it gives the guide to interpreting the body analysis. Would be glad to share it with you if you're still wondering!

I am have the same problem as bebe_66.  I have a scale that measures your weight, bone density %, your muscle %, your water %, and your fat%, but there is now guide to use to interpret what it means.  Can anyone help

Bioelectrical impedance does not really work. So the numbers you are getting from your scale are not much use.


I have a similar scale that measures all of those also.

It gave my bone density a 9.1 on my scale which is extremely high.  I just couldn't figure out how it figures out bone density.

If you were to get on there in the morning after you pee, wouldnt your tissues be a little dehydrated and make the reading drastically different from when you are hydrated? Sounds like you couldnt really trust the readings to me. I mean, the weight would be acurate maybe, but then you could just buy a regular scale. That has been the thing stopping me from dropping $ on these things.

When they do the bone density test at the doctor's office they immerse your heel in water. I would get one done there is you are concerned about osteoporosis. I wouldn't trust a commercial scale with something that important.

Sure, I just bought one today! The info you are looking for is on the flip side of the instruction paper.  What I would like to know is how accurate the bone density percentage that it reads is. Do you know?  Smile



I don't think those are accurate, to get a good reading you have to do the water test. The only number you can be sure of is your weight. They are cool gadgets though!

I've gotta say this is really annoying.  I was looking for this answer, too, because like many others, the book that came with my scale doesn't give the ranges for everything.  Mainly water and body fat, which is easy enough to figure out on your own.  I'm interested in bone density, as mine is coming up 4.4 and I have no idea if that is normal or not.  I wish people wouldn't post just to tell others it doesn't work, or that they should go to a doctor.  That is simply their opinion, and (mine is) these scales do actually work, because, if nothing else over time you can see your body fat decreasing and your muscle mass increasing.  This tells you you are losing what you want to (fat, not muscle) and that you are steadily reducing your fat and increasing your muscle.  This is very useful especially when your lbs are not changing, or even increasing.  I have had instances where I have stayed the same weight, but my fat %, muscle % and my actual measurements have decreased considerably (or increased, with muscle).  This tells me I am not at the plateau my scale seems to be suggesting I am, and there are still changes occurring that I otherwise wouldn't know about.  It also, to a degree, tells me if I gain both weight and muscle, and my fat stays the same or decreases, that I am not putting on "bad weight".  It's just a normal part of getting stronger for the first while.  Additionally, really, come on.  Go to see your dr because you want to know if your bone density reading is normal?  I would go see my dr because I was worried I might be developing osteoporosis.  But I'm not.  I'm a normal, healthy 34 year old that doesn't have any concerns about my bones, and I wouldn't justify that as a good reason to go get an (at this point) unnecessary medical test that would waste time, money and resources for someone who really could use that test.  I'm just curious.  I'd like to know if my bone density reading is considered normal.  That is it.  And I have used two of these scales (one broke) for the better part of a year and I can tell you that although I could not say if the percentages are exact, they are certainly accurate in that they do not go yo-yo-ing all over the place and are consistent over a long period of time, as well as from one day to the next.  Anyway this information is hard to find--so far I have been unsuccessful--so it would be nice if people who chose to respond, responded to the question.  Had it been, these are my results, do you think these scales are accurate and I can trust these numbers?  would be one thing.  But it wasn't, and it sounds to me like there are a number of people out there in the same boat, who would just like to know what it means and the statistics are.  These scales are excellent for keeping you on top of your results, and getting where you want to be, and keeping you motivated as you see them improve--and catching it if they were to slide in the wrong direction, like losing muscle or gaining weight or increasing fat %.  Whether they "work" is a very subjective thing.  And even in a very literal sense there is just as much for them as against them, (like everything else in health out there) unless you are going the caliper route, then, sure that will be more accurate.  But are you going to go get that done every day?


Anyway, back to the question at hand, which was bone density (sorry I do not know either) and your muscle % is pretty good (but I am basing that on my own which is around 36% now) but I am going to be increasing it a lot more--and I don't know what your body type is.  But I will guess based on your very low fat % that your corresponding muscle % is very good, and would make you a very fit person (but again that is just based on my understanding of fat and muscle % and my own experience, and assuming this scale is accurate).  I think the reason no one seems to include that one in the handbooks is there are so many variables.  

And there is always the simplest of all:  look at yourself.  (I know, you didn't need me to tell you that! lol)  But seriously, at my most fit, I always got out of the shower every time and noticed how fit and toned I looked, how my body looked sculpted and toned and I didn't have any visible fat.  I didn't think all of those things of course, but it was always a pleasant surprise, kind of like "I look good!"

Any way, good luck, it sounds like you are doing really well :)

The body fat readings of BIA (body impedance analyzer) scales have been tested against underwater weighing in numerous trials.  I don’t recall the details of the reports I read, but in general the average error is reported to be around 5%.  (To be clear, that is not five percentage points as is “14% is five percentage points lower than 19%”, that is 5% as in “18% is 5% lower than 19%”.) 

However, there are some significant caveats.   First, that is the average error among the test group of 20 or 30 or 50 people.  The error for any one individual in the group could be greater or lesser.  And indeed the standard deviation of the error is significant.  Second, BIA scales are designed for a particular set of bodies.  An intermediate age group, not children and not elderly.  An typical body type, not extremely muscular/lean and not extremely obese.  And there are some racial differences (blacks tend to have more dense bones, see race.html
and the scales don’t ask for your race).  Third, BIA scales can’t, as far as I know, distinguish between the contents of your digestive tract (food, water, and waste) and the mass of your body (muscle, fat, bone and organs).  Fourth, in theory the BIA scales with handgrips as well as footpads “should” be more accurate, but I don’t know of any evidence that they are.  Fifth, the BIA scales that seem to be tested most often are Tanita and Omron.  I haven’t any idea if the other brands use the same algorithms.

Bottom line, you can’t assume the BIA scale is giving you a precise estimate of your body fat.  However, if you use it consistently (measuring in the morning, after toilet, before eating/drinking), I think the BIA scale can give you a reasonable sense of your trend from week to week or month to month. 

In other words, if it says you are 19.7%, you might or might not get the same estimate from other body fat measurement methods such as calipers or underwater weighing.  Of course, you could check your BIA scale against those other methods and get a pretty good idea of the error for your particular scale and body.

But if you get your own BIA scale and several measurements over the course of several mornings now average to 19.7%, and in a few months several measurements over the course of several mornings average to 18.7%, it is pretty likely that you’ve lost more or less 1 percentage point of body fat. 

Of course, you could simply get a $20 set of skinfold calipers and do the same thing, or simply get good at assessing yourself in the mirror.  And given your goals are about fitness/strength, maybe you should focus directly on those measures (heart rate, weight lifted, etc) instead of body composition.  But if you want a new scale anyway, the BIA features come fairly cheap.

I don’t know how accurate the BIA scales are with muscle percentage, bone density, visceral fat, or other things they claim to measure.  I haven’t ever looked for test results on those things, and it isn’t clear what some of those measurements even mean (e.g., what does “4.8 bone density” actually indicate?)

Here is an abstract (summary) of some testing of aTanita BIA scale's muscle percentage measurement function. Report published Aug 2011. It concludes the Tanita product overestimates muscle percent and underestimates fat percent in older women, while underestimating muscle percent and overestimating fat percent in older men. This was in a test group of European ethnicity, men and women averaging 69 y/o.

This only applies to one model of BIA scale, but gives you an idea of why you can't assume themuscle percentage reading isa precise estimate.

"Segmental determination of muscle and fat mass (MM, FM) attains growing importance for judging effects of training and malnutrition in older people. This study evaluated the reliability and accuracy of segmental bioelectrical impedance analysis (sBIA) for use in older people. In 72 (40 men, 32 women) healthy elderly (mean age 69.0 4.8 years), the MM and FM of right and left arm (RA, LA), right and left leg (RL, LL), and trunk were determined by sBIA (BC-418-MA, Tanita) and dual-energy X-ray absorptiometry (DXA) as a reference method. The sBIA provided in both sexes reliable values for limb and truncal MM and FM, except for MM of RL in women. The accuracy of sBIA displayed sex-specific bias. For MM, accurate values were noted for men's trunk and women's limbs (except LA). By contrast, MM was significantly underestimated in men's limbs by 6-18% and overestimated in women's LA (13%) and trunk (14%). Estimates of FM were accurate for men's arms as well as women's legs and trunk. However, FM was significantly overestimated in men's legs (34-37%) and trunk (60%), but underestimated in women's arms (27-35%). The proportional deviations of sBIA estimates from DXA values for limbs and trunk were significantly related to the respective MM or FM. The sBIA tends to underestimate MM in men and to overestimate in women. The reverse occurs for FM. The actual equations of the Tanita device may not completely represent the European older population and should be partly revised.

Last bit from me - thanks for the opportunity to learn about BIA and muscle mass percentage measurements, by the way - here is a study in which some researchers explored how accurate (or not) BIA estimates of muscle percentage could be. It shows you how the BIA algorithms are developed, the range of error that you might expect from a BIA process, and some of the sources of error. Note that they developed the algorithms on Caucasians and then found that they underpredicted muscle mass in Asians. The consumer BIA scales are developed using a similar process. ng

Anyway, sorryif this is boring. I am rather pleased to see there is some possibility that my BIA scale is underestimating my muscle mass (as I am Asian), so I am content to quit reading up on the topic. Stop when you get the answer you want, I say.


I too have a scale that measures body fat, muscle, water weight, and bone mass. I am now 40, and have been tracking these figures for the last several years with out much concern. I noticed recently, my bone mass decreased (based on the scale) from 4.4% to 4.2%. I researched online to understand how this compared for my age group, and was concerned that it was out of range by SEVERAL percentage points. This, coupled with the fact my mom has osteoporosis, prompted me to visit the Dr.

What I learned, was that there appears to be no direct correlation, between the scale results and the health of my bones. For example osteopenia is defined as a standard deviation of -1 to -2.5. My official bone density readings came in on average around a -.4 (four tenths) - which is healthy.

I wouldn't be too concerned about the scale reading on the bone mass, even if it "appears" to be outside of the normal range. I think it's great to have it checked out if you can. It's kind of like gingivitis - you don't want to wait to hear you have it from the dentist before you start flossing. Once you lose Bone, you can't regrow it:(. There are younger women diagnosed with this condition, and it's best to be proactive (again, if you can).

Hope this helps!!

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