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Thread: Body fat

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    Body fat

    What is your preferred way to check % body fat?

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    Huachuca Rider webist's Avatar
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    Calipers
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    RAGBRAI. Need I say more? Steele-Bike's Avatar
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    Originally posted by flyefisher
    What is your preferred way to check % body fat?
    Girlfriend

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    L41
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    Covert Bailley gives a formula using body measurements. Not an expert on this as far as its relative merits, just offering what I have read. (He states that it is +/- 2% accuracy compared with underwater immersion tests.)

    Women 30 years and younger:

    hips +(.80*thigh) - (2Xcalf) - wrist = % body fat

    Women over 30:

    hips + thigh -(2Xcalf) -wrist = %body fat

    Men 30 years and younger:

    Waist + (1/2hips) - (3Xforearm) - wrist = %body fat

    Men over 30:

    Waist + (1/2hips) - (2.7Xforearm) - wrist = %body fat

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    Covert Bailley gives a formula using body measurements. Not an expert on this as far as its relative merits, just offering what I have read. (He states that it is +/- 2% accuracy compared with underwater immersion tests.)
    Do you have a link that gives details about the derivation of these formulae? I'm curious about what magically happens on a persons 30th birthday that would make their body fat spontaneously increase by 0.2 thigh diameter or 0.3 forearm diameter, depending on gender.

    I know, I know - all formulas like this are based on averages - I'm just curious and would like to see the rationale for this particular derivation, as it isn't one I've seen before.

    Thanks

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    Mirror.

    At this stage there's no use using any formulae to measure my body fat. It's all too obvious that I have far too much.

    I dream of having to use calipers or a formula.

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    L41
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    Originally posted by OldDog


    Do you have a link that gives details about the derivation of these formulae? I'm curious about what magically happens on a persons 30th birthday that would make their body fat spontaneously increase by 0.2 thigh diameter or 0.3 forearm diameter, depending on gender.

    I know, I know - all formulas like this are based on averages - I'm just curious and would like to see the rationale for this particular derivation, as it isn't one I've seen before.

    Thanks
    So far, I've not been able to find the information you're requesting, either in the book on in the web. The book is "popular", not scientific in scope, so it's meant to be easy for people to understand and follow, not detailed, explained, and footnoted to the nth degree, unfortunately. I did find a scad of other formulae floating around out there, and that seems to be par for the course, at least for what turns up in general web searches - no one seems to mention what their favorite calculations are based upon.

    I don't see an explanation for why the switch at age 30. He discusses some of the physical changes with age - loss of muscle mass and bone density that would cause changes in body composition, but this would seem to already be accounted for when he advises people to adjust their weight downward as they get older to keep their body fat constant as they lose lean body mass. He definitely isn't advising people to let the fat pile on after they reach a certain age.

    The only website with a reference to this I have found so far is http://www.healthcentral.com/cooltoo.../bodyfat1.cfm. It does not provide the formula, but it does use a calculator that I am pretty sure uses the same formula, as the reference book is the same that I quoted from - "The Ultimate Fit or Fat" by Covert Bailey.

    Another tool at the same site yielded a rather interesting/questionable result for my own measurements - using your % body fat and and current weight, it calculates your ideal weight. For me, female, 5'6" and 274 pounds, it calculated 33% body fat (which seems quite low), and calculated that I needed to loss 39 pounds of fat for an ideal weight of 235 pounds, purportedly at 22% body fat, which seems extremely high (height/weight or BMI charts give 155 pounds as the top weight with 146 as ideal.) How does this thing "know" that at 235 pounds, I'm going to be 80 extra pounds of muscle over my "ideal" weight, not fat? (For sure, I wouldn't accept that as a final weight without validation by more accurate form of testing by someone that knows what they are doing.)

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    The equations relating body fat to body dimensions are extremely unreliable and inconsistent. Caliper-based and electrical resistance-based measurements are far better, but I suppose immersion/buoyancy is the best. I just watch how much pinchable flab I accumulate around the navel.
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    I don't see an explanation for why the switch at age 30.
    Maybe I'll have to check out the book. Based on his formula, were I 29 my body fat would be 9%, but since I'm 36, it is 12.6%. I'm inclined to believe the latter figure (I'm in good shape, but not THAT good), but I don't think I'm losing lean body mass - in fact I'm pretty sure that I've increased it since I was 29, since I have gotten much fitter in the last 7 years.

    I think you are right about the link you provided using the same formula - it tells me 13%, but if I change the age to 29, it tells me 9%. The 'ideal weight' thing also tells me that for my height (6'2") and current weight (191) I need to gain 4 pounds to be at my ideal body weight - not. If I'm going to do the Bicycle Tour of Colorado and climb those hills next summer, I need to get DOWN to 180 or below, not go up. I guess its all about averages again. And people getting fit by biking, no matter how big or small, are not the 'average' couch potato.

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    that formula says I'm 6% body fat.... i KNOW that's way off... I have very large forearms though...12.5"

    34" waist... I'm 5'10 and 186#

    i was just thinking today how much i want to be 5% body fat... so i know it's all wrong :-D

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    L41
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    The neatest thing about posting comments on things I really don't know about is that I learn so much from the responses

    And here I was, making plans for those 80 extra pounds of muscle, thinking maybe I would have a new career in pro football or wrestling in my middle age

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    based on my feeling (basically guessing), best to worst measurements:
    1) immesion - never done it, but i think it's complicated and you measure your volume displaced in the water, then subtract your lung capacity (or measure somehow when fully exhaled) and then divide by your weight somehow -- i don't know the formulas
    2) calipers - usually 3 or more places - i think back of arm, waist and thigh are the most common - again i don't know formulas, but i think there are different ones that have different measurements and/or weight them differently
    3) electrical resistance - these measure the difference in conductivity between fat and muscle -- not sure, but i think things like the device as well as your hydration level would effect this measurement a lot (mine done on a basic cheap handheld during my Lactacte Threshold test last Spring was 10.5% which i think is way too high -- i know i've lost muscle and my body fat is up a bit from the 5% or so about 3 years ago, but i don't think it's that high (more like 8-9% i think) --- i'm 6'1" and 165lbs just for reference)
    4) formulas based on weight-height-diameters -- i don't see these being very accurate
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