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SIMONEKP Posts: 2,760
7/7/13 7:02 P

I agree that the scales are not accurate, mine measures hydration level also and whenever my hydration level drops, my scale shows a higher BFP.

MOTIVATED@LAST Posts: 15,443
7/6/13 9:24 P


It's probably worth getting your BF tested with at a gym with calipers. You will then have a benchmark against which you can calibrate the online methods. (eg 32% caliper = 41% army)

You can use the online (and free) methods to track changes over time, without having to constant go back to the gym.


MPLANE37 SparkPoints: (78,856)
Fitness Minutes: (77,601)
Posts: 2,170
7/6/13 9:15 P

Those formulas are targeted for specific populations.The formula is accurate if you are a typical person in the targeted population. If you are not, that formula will be off by a lot.

If you want to know your body fat % anywhere near its real value, you need to find a gym where an experienced person can take readings on your body using a skinfold caliper. That will yield a body fat % quite close to your real body fat %.

PTOSIS Posts: 463
7/6/13 6:45 P

Different Body fat calculators come up with very different numbers. Depending which online body fat calculator that I am using my BFP is anywhere from 26.9 to 41%!!!

Which one should I use? The army one gave me the highest at 41%.

Age 52
weight 184
height 66.75
waist 38
hips 43
neck 14.5
forearm 9.75
writst 6.375
BMI 29.2 emoticon

ROSEBOMB Posts: 345
11/28/12 8:43 A

We ran the device three times while I held as still as possible - and I waited to do this until about 2 hours after I ate - twice the number was the same and the third time it was different, but only by .02% ... I figure it's fairly accurate if it can give three really similar readings back to back.

MOTIVATED@LAST Posts: 15,443
11/28/12 5:30 A

Handheld scanners are normally DEXA scanners - these are reasonably accurate.

MPLANE37 SparkPoints: (78,856)
Fitness Minutes: (77,601)
Posts: 2,170
11/28/12 4:27 A

How does the apparatus work? I imagine it works by measuring the resistance to electrical current, i.e. bioelectrical impedance (see
). That method is sensitive to water content of the body. Any fluctuation in water content will alter the measurements, so not reliable at all.

It may be useful to get a broad idea of what your body fat % is though.

ROSEBOMB Posts: 345
11/27/12 8:41 A

Based on all this, I think my aim should be to lose about 30 pounds ... I just got the fitbit and that is helping a lot. The BFP came from this little handheld device at my gym. I plan on monitoring it monthly. I figure using the same device each time will help me stay fairly accurate.

MOTIVATED@LAST Posts: 15,443
11/26/12 11:33 P

Bathroom body fat scales are indeed easy to use and at no cost beyond the initial purchase.

But they are also rather inaccurate, and the reported BFP numbers can vary by several percentage points from day to day due to changes in your hydration levels, rather than any actual change in your body fat.


KNELKINS SparkPoints: (0)
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Posts: 127
11/26/12 5:51 P

If you are about 43% body fat at 232 pounds, that means you have a lean body mass of 132 pounds and a total body fat mass of 100 pounds. To reduce your body fat percentage to 31% without losing any lean body mass whatsoever, you would need to lose 42 pounds of body fat, bringing your final weight to 190 pounds. However, most people lose at least a small amount of lean tissue when losing a significant amount of weight, so your final weight may be lower than 190 pounds if you lose muscle mass alongside fat. To prevent muscle loss, incorporate a challenging full-body strength training program utilizing compound movements that work large muscle groups two to three times per week into your exercise routine. Good luck!

MOTIVATED@LAST Posts: 15,443
11/26/12 5:46 P

At 232 lbs, 42% BFP represents 97 lbs body fat, and a lean mass of 135 lbs. And 135 / 69% = 195 lbs. So you would need to lose 37 lbs.

Of course, this is just the math. In real life, lean mass doesn't stay the same when you lose weight, so the reality will probably not match the formula, and you will probably have to remeasure your body fat and reassess your goals along the way. But hopefully this will give you some kind of initial guide.

FAVALL SparkPoints: (71,177)
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11/26/12 5:29 P

I recommend that you purchase your own body composition bathroom scale. See my blog outling my experience and the value of this great INEXPENSIVE tool

ELLGEEBEE SparkPoints: (1,038)
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Posts: 128
11/26/12 5:18 P

If your current weight is 232 then I believe you need to aim to reach 168-169 lbs to get to 31% body fat. I used basic math/algebra and got this, but I'm a little rusty so I could be off here. :)

SOCAL_LEE SparkPoints: (43,325)
Fitness Minutes: (97,762)
Posts: 246
11/26/12 5:07 P

Oh, I see where you're coming from. Maybe an expert will weigh in (sorry! :)) but I think, sadly, the answer is no, there's no set formula. Because everyone is going to lose in different ways, and depending on what physical activity/ies you're doing and what you're eating, you're going to lose a distinct proportion of fat/muscle/water. The only thing I can think of would be to get a very detailed, specific consultation -- did you get measured in a water tank? -- and get some pointers from that, but I still don't think they can tell you "once you've lost xx pounds, your body fat will be at 31%".

ROSEBOMB Posts: 345
11/26/12 4:56 P

Thanks, both of you! I appreciate the words of support. Isn't there some kind of math formula though that should tell me exactly how many pounds to lose to go from 42.56% to 31%

PSCHIAVONE2 SparkPoints: (20,650)
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11/26/12 4:48 P

I concur, the best thing you can do is get on a regular exercise plan. You can strength train without using weights. If you do go the weight route, it is important to use compound exercises. I make sure that I strength train and then hit the cardio in the same session. By doing both you will maximize your calorie burn. I have tried cardio first and then strength training also. Both ways have more benefit then just doing cardio one day and then strength the next. This coupled with a healthy eating plan will get you the best fat reduction possible.

SOCAL_LEE SparkPoints: (43,325)
Fitness Minutes: (97,762)
Posts: 246
11/26/12 3:52 P

By "what's the formula", are you asking "how do I decrease my body fat percentage?" If so, I think the answer is to continue to bring down your overall weight, since a lot of that is fat. When we lose weight we lose muscle as well as fat, so my best recommendation is for you to continue to exercise and to incorporate some serious strength training into your workouts if you haven't already done so. That will help you retain and build muscle while shedding fat. The book _New Rules of Lifting for Women_ is a very good place to start, and should be available at your local library. I have friends who recommend _The Female Body Breakthrough_, too. Even if you're already lifting weights, I find that the programs in these books help me be more systematic and organized about my strength training, ensuring that I do it 3x/week and that I train every major muscle group. There are a lot of good options out there for strength training programs. Good luck!

ROSEBOMB Posts: 345
11/26/12 3:41 P

Our gym just got a body fat percentage thingy ... I tested three times and then averaged the numbers (which were all very close anyway). So, now that I have my body fat percentage, what do I do with it? Mine is really high ... 42.56%. I'd like to bring it down to 31%, but what's the formula?

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