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Weight Loss Forum / Low Carb / August 2006BMI and muscle on an electronic scale
Hello everyone, Was wondering something: on my Tanita scale, it is said that a very muscled person should not use it to monitor accurately its body fat. I Guess that it makes the BMI falsely too high or too low. But in wich way? Thanks for your answers. Huey You're not muscular enough to worry about it. HTH > Hello everyone, > [quoted text clipped - 6 lines] > > Huey > Hello everyone, > > Was wondering something: on my Tanita scale, it is said that a very > muscled person should not use it to monitor accurately its body fat. > I Guess that it makes the BMI falsely too high or too low. > But in wich way? My Tanita supposedly measures body fat, but doesn't seem accurate at all. I believe there is a set mathematical formula built in that is based on average height and weight. You can test this out by increasing the height in the personal settings and watch the fat % go down when you step on it. I'm 5'11" and 180 lbs. It shows me at 19, or sometimes 20% body fat. If I input 6' 3" in the settings and weigh myself, it says I'm 12%. If I have it set at 5' 11" and lean on the sink to make my weight lighter on the scale to 165 lbs, the fat % comes out at 14%. I was under the impression, when I shelled out $80, that it would accurately measure body fat. There are some "electric pads" on the scales that they claim measures the fat. There must be some sort of current that goes through it because it shows an error message if you have shoes on. It does appear, though, to be right on with just the weight measurement, comparing it to 2 different mechanical beam scales. Over all, it is not worth the money in my opinion. > Thanks for your answers. > > Huey >>Hello everyone, >> [quoted text clipped - 22 lines] >> >>Huey Copied from: http://en.wikipedia.org/wiki/Body_fat_percentage The key idea is that the electrical resistivity of fat, muscular and skeletal tissues are different, and therefore, electrical resistivity of the body COULD be a convenient way to measure or estimate body fat percentage. It is far from perfect. --------------- Wikepedia article clipping ---------------- Bioelectrical Impedance Analysis (BIA) This method can be conducted accurately in the laboratory or at home with less accuracy, though this version is more affordable. The general principle behind BIA: two conductors are attached to a person's body and a small electrical charge is sent through the body. The resistance between the conductors will provide a measure of body fat, since the resistance to electricity varies between adipose, muscular and skeletal tissue. Criticism of this methodology is based on where the conductors are placed on the body; typically they are placed on the feet, with the current sent up one leg, across the abdomen and down the other leg. As men and women store fat differently around the abdomen and thigh region, the results can be less accurate as a measure of total body fat percentage. Another variable that can affect the amount of body fat this test measures is the amount of liquid an individual has consumed before the test. As electricity travels more quickly through water a person who has consumed a large amount of water before the test will measure as a lower body fat percentage. Less water will increase the percentage of body fat.  Signature1) Eat Till SATISFIED, Not STUFFED... Atkins repeated 9 times in the book 2) Exercise: It's Non-Negotiable..... Chapter 22 title, Atkins book 3) Don't Diet Without Supplemental Nutrients... Chapter 23 title, Atkins book 4) A sensible eating plan, and follow it. (Atkins, Self Made or Other) > >>Hello everyone, > >> [quoted text clipped - 54 lines] > lower body fat percentage. Less water will increase the percentage of > body fat. I understand how it's supposed to work, but I don't think the Tanita scales function like that. There are certain inputs that you put into the "personal settings". Male or female, height and current weight. If you re-set the height portion, it comes out as a lower fat % at the same weight. This seems to me like they are using a formula to guestimate what your fat % should be at certain heights and weights based on averages. If I hold on to the sink to make my weight less on the scale by 15 lbs, it shows that I am at a much lower fat %. 14% instead of 19%. If I hold a 25 lb weight, the fat % shows 24. There should be no difference in my electrical conductivity at 165 lbs, or at 200 lbs. If anything, the increase weight I'm holding should theoretically cause my feet to be more conductive from the pressure on the metal pads and show me as less % fat. It also doesn't register a different fat % whether my feet are damp, or dry. I think it is all done by a calculation. There may be some good devices out there that actually measure these things properly, but this technology doesn't seem to be within the Tanita scale. > -- > 1) Eat Till SATISFIED, Not STUFFED... Atkins repeated 9 times in the book > 2) Exercise: It's Non-Negotiable..... Chapter 22 title, Atkins book > 3) Don't Diet Without Supplemental Nutrients... Chapter 23 title, Atkins > book > 4) A sensible eating plan, and follow it. (Atkins, Self Made or Other) >>>>Hello everyone, >>>> [quoted text clipped - 98 lines] > out there that actually measure these things properly, but this technology > doesn't seem to be within the Tanita scale. You and I do not know what algorithm (mathematical relatinships) are programmed into the scale. You are making "guesses" as to what use, if any, is made of the parameters of weight (measured), electrical resistance (possibly measured), sex (user input) and height (user input). It is absurd to thing that from weight and height alone that the percentage of body fat can be reasonably assessed. After all, we have discussed the effect of muscle build on the process. I have heard you twice reiterate that if you input a different height or ficticiously remove some of your weight ( force acting vertically upon the scale), then the results change. The above proves nothing. Except that among other things, the force on the scale and the user input height are used in the programmed logic of the computer chips in the scale. If you scale didn't give different readings under the conditins you have twice described, it would be worthless junk. You are trying to prove something, somehow. That is clear. I suggest that you actually read up on the subject, if it is still of interest to you. It isn't of much interest to me, however. Good luck, Jim Signature1) Eat Till SATISFIED, Not STUFFED... Atkins repeated 9 times in the book 2) Exercise: It's Non-Negotiable..... Chapter 22 title, Atkins book 3) Don't Diet Without Supplemental Nutrients... Chapter 23 title, Atkins book 4) A sensible eating plan, and follow it. (Atkins, Self Made or Other) > >>typically they are placed on the feet, with the > >>current sent up one leg, across the abdomen and down the other leg. > > And the composition of my legs and abdomen do not change when I hold a 25 lb weight over my head, but the scale assumes all weight gain is fat. > You and I do not know what algorithm (mathematical relatinships) are > programmed into the scale. No I don't, but it sure looks like a pre-programmed table. > You are making "guesses" as to what use, if any, is made of the > parameters of weight (measured), electrical resistance (possibly > measured), sex (user input) and height (user input). My guess is that the scale is useless. > It is absurd to thing that from weight and height alone that the > percentage of body fat can be reasonably assessed. After all, we have > discussed the effect of muscle build on the process. Yes > I have heard you twice reiterate that if you input a different height or > ficticiously remove some of your weight ( force acting vertically upon [quoted text clipped - 6 lines] > If you scale didn't give different readings under the conditins you have > twice described, it would be worthless junk. There is also an age input. If I input 25 instead of 48, it is assumed that my weight is more muscle, as it shows up at 16% fat. My Dad is within 5 lbs of my weight, but 5" shorter. His fat % comes out at 19% as well, yet he is obviously chubbier. On discussions, he has stated that in his younger years, his ideal weight was between 155 and 160. The scale assumes it is me stepping on it ( since the weight is so close ). His composition is certainly different than mine. > You are trying to prove something, somehow. That is clear. I'm not trying to discredit you. You pointed out that the results are not always accurate. I was agreeing with that, with my own experiments. The weight gained or lost on the scale is always assumed to be fat. If it sounds like I was being argumentive, it was not my intention. > I suggest that you actually read up on the subject, if it is still of > interest to you. I think that a mirror is more accurate. > It isn't of much interest to me, however. > [quoted text clipped - 8 lines] > book > 4) A sensible eating plan, and follow it. (Atkins, Self Made or Other) > I think that a mirror is more accurate. Agreed. And the pinch test of the abdominal skin/fat. Your scale sounds like is pre-programmed and useless as a fat measuring device. LW Re-Start - 7/5/06 - 170lbs Today - 156 lbs Goal - 130 lbs Height: 5'6" Female. Age: 61 Don't worry about what people think, they don't do it very often. =================================== ::: I think that a mirror is more accurate. :: :: Agreed. And the pinch test of the abdominal skin/fat. :: :: Your scale sounds like is pre-programmed and useless as a fat :: measuring device. Those scales are well-known to be useless at determining bf % accurately. Some think that perhaps, when used correctly, they are useful for determining the trends, as in increaseing or decreasing bf%. However, looking in a mirror, measuring one's weight, or looking at how clothes fit are all better, IMO. If you really want to get bf info, use the caliper method and find someone skilled at doing that measurement. However, > looking in a mirror, measuring one's weight, or looking at how clothes fit > are all better, IMO. This is the method I use. It works well and doesn't cost a penny. LW Re-Start - 7/5/06 - 170lbs Today - 156 lbs Goal - 130 lbs Height: 5'6" Female. Age: 61 Don't worry about what people think, they don't do it very often. =================================== > I understand how it's supposed to work, but I don't think the Tanita > scales function like that. There are certain inputs that you put into the > "personal settings". Male or female, height and current weight. It's not a miracle device, you know ;-) What I understand is that the scale sens electricty on one side and just takes a note of the time it gets to get to the other side. So, of course, if you measure 2,20m there's a big difference. I think it's a combination of several datas, really. But it can help sometimes. For instance: When I read that I suddenly lost 2kg on my scale *but* that my BMI is 2 points higher than last time, I can easlily deduce that I must miss some water and that my real loss is less than 2kgs. So I can prepare myself not to be "disapoited" next time i get on the scale. Same thing the other way around. Huey > As electricity travels more quickly through water a person who > has consumed a large amount of water before the test will measure as a > lower body fat percentage. Less water will increase the percentage of > body fat. This is very useful to keep in mind, I think. Huey > Hello everyone, > [quoted text clipped - 6 lines] > > Huey Well, we know now how water affects BMI reading, but can it be extended to muscle? I'm still wondering. The underlying question is now: is muscle conducting electricity better or not than fat. Furthermore, when one has adopted LC as their "way of eating", we know their muscles contain much less water than usual since most of the glycogen is gone. How would that influence the reading? Am I going to far there? ;-) Huey >> Hello everyone, >> [quoted text clipped - 19 lines] > > Huey Rather than "think", have you tried to google for the algorithms of this, or for the electrical resistivity of muscle, fat and skeletal tissues? It is fun to "think", but research can be useful. Jim Signature1) Eat Till SATISFIED, Not STUFFED... Atkins repeated 9 times in the book 2) Exercise: It's Non-Negotiable..... Chapter 22 title, Atkins book 3) Don't Diet Without Supplemental Nutrients... Chapter 23 title, Atkins book 4) A sensible eating plan, and follow it. (Atkins, Self Made or Other) >> Well, we know now how water affects BMI reading, but can it be >> extended to muscle? [quoted text clipped - 16 lines] > > Jim I think you are making a reference to another post. Otherwise I don't really understand what you mean. I'm sorry Jim, but I think you are a bit aggressive on this one, aren't you? :-) When I ask a question here on this NG, it's that I want to avoid many confusion that lies out there on the web; I just prefer sometimes ti rely on some people's experience. And,as a matter of fact, yes: "to think" is fun. Huey |
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