Body Fat Calculators: Voodoo science

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mromnek
mromnek Posts: 325
in Fitness and Exercise
I have seen people on here concerned with their % body fat. I think that is a fantastic metric to use with weight loss plans. It accomplishes two things. First, it tracks those fat lbs as they come off. Second, it allows a person to set a realistic end weight goal, based upon their desired body fat percentage.

However, do not gravitate toward the body fat calculators. The most common is the US Navy's "Rope and Choke," as we called it years ago. I knew back when I was in the Navy that the accuracy is +/- 20%. When I was at my peak fitness, The Navy rope and choke said I was at 26% body fat (obese: unable to re-enlist). At the same time, I was 13% by caliper measurement (not even overweight by Navy standards). So, for me, there was a 13% variance between the body fat calculator and caliper measurement.

Earlier this month, I went ahead and took my measurements and plugged them into the body fat calculator. In full disclosure, here are the results from Feb 1 and today.
Feb 1
Today
Difference
Weight----264.6
260.4
( - ) 4.2 lbs
Waist
52
51
( - ) 1 inch
Hips
46
45.5
( - ) .5 inch
Neck
18
18
no change
Chest
51.5
50
( - ) 1.5 inch
Wrist
7.5
6.75
( - ) .75 inch
Forearm---12.5
12.25
( - ) .25 inch
% BF
35.78
36.82
( + ) 1.04%

So according to the inaccurate body fat calculator, I lost 4.2 lbs and 4" total measurements, and gained a bit over 1% body fat.

Can you imagine how I would feel if I put faith in that measurement. Can you believe that the US Navy uses that calculation to determine people's career fate? I would advise anyone to avoid using the body fat calculators. If you belong to a health club, ask for caliper measurements. Find a hydrostatic measurement otherwise. If you are using these tape measure calculations, give them up, they are bad for your self esteem!!!

Replies

  • jbuffan218
    jbuffan218 Posts: 275 Member
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    This is so ironic.
    I literally JUST did the tape measure version . I mean the site is still up on my computer. I plugged my numbers into a BF calculator and got a result. I am not confident enough to reveal the results but lets just say that at 5' 10' 50 yrs old and 165 pounds.......I am "acceptable" but only by 1/10th of a percentage. Ok, so that really makes me feel better. So in other words if I were to gain 1/10th of 1% in BF I would be obese. Seriously?
    I have an option on my scale that will also tell me BF % but have read here and other places that the scale type is also in-accurate.
    So, unless a person is able to spend $ on the water emmersion type test are any of the over the counter type tests accurate???

    And should I really care?
  • gym_rat
    gym_rat Posts: 94
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    My husband is in the army and it's ridiculous how they measure the bodyfat.
    go to http://550cord.com/products/info.asp?ProductID=7&product=Army-Fitness-Calculator and see for yourself.
    There are so many ways to "trick" the system and how you can push out your neck, etc.
  • mromnek
    mromnek Posts: 325
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    The hydrostatic measurement is accurate, as well as the electrical resistance method. Both of those methods typically require a "nominal" fee. I would say that if you did it once in a while, it won't break the bank.

    Another close finisher is the caliper method. I had it done for free when I was a member of Bally's Health & Fitness (20 years ago). I would bet that most health clubs can do it for you, if you are a member of a club. There are a number of caliper methods, but I am not familiar with how they compare accuracy-wise. But any of them would be more accurate.

    The rope and choke is kinda like the BMI... it is a starting point. The BMI might be accurate over a large population, but you will have outliers. Same with the rope and choke. Do I believe my current BF% by rope and choke... within 5% or so, sure. Would I depend on it, no way.

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