body fat %

weathergirl320

what exactly is a body fat %? and how do you calculate it?

mtnbiker1

I'm definitely no expert but simply put, if you are trying to lose weight, keeping track of body fat % is just as, if not more important, than just keeping up with pounds lost. The reason is if you weigh yourself and see you've lost weight it could be fat OR muscle and you don't want to lose muscle. There are several ways to measure body fat. Calipers or hand held electronic devices are probably the most affordable. Some methods are supposedly more accurate than others but as long as you choose one method and stick with it and check your body fat consistently each time (same time of day, before eating, etc.) that's what matters. GNC sells both the caliper and hand electronic ones. Hope this helps.

Acg67

http://www.leighpeele.com/body-fat-pictures-and-percentages

And more on various ways to measure it and the pitfalls of each way


http://weightology.net/weightologyweekly/?page_id=146
http://weightology.net/weightologyweekly/?page_id=162
http://weightology.net/weightologyweekly/?page_id=175
http://weightology.net/weightologyweekly/?page_id=218
http://weightology.net/weightologyweekly/?page_id=283


http://www.bodyrecomposition.com/fat-loss/measuring-body-composition-part-1.html
http://www.bodyrecomposition.com/fat-loss/measuring-body-composition-part-2.html
http://www.bodyrecomposition.com/fat-loss/problems-with-measuring-body-composition.html

weathergirl320

so basically you need an instrument to do it? because i saw a scale in the store ( just a normal bathroom scale) and it claimed to be able to measure body fat %. it seemed like a gimmick to me though.

Acg67

so basically you need an instrument to do it? because i saw a scale in the store ( just a normal bathroom scale) and it claimed to be able to measure body fat %. it seemed like a gimmick to me though.

It uses BIA...


Changes in body composition during weight loss in obese subjects in the NUGENOB study: comparison of bioelectrical impedance vs. dual-energy X-ray absorptiometry.

Verdich C et al. Diabetes Metab. 2011 Jun;37(3):222-9.

"RESULTS:

At baseline, BIA significantly overestimated FFM and underestimated FM (by 1-3 kg on average) compared with DXA, and the limits of agreement were wide (mean ± 7-8.5 kg). "


A comparison of dual energy X-ray absorptiometry and bioelectrical impedance analysis to measure total and segmental body composition in healthy young adults.

Lehy S et al. Eur J Appl Physiol. 2011 May 26

"BIA was found to underestimate the percentage total body fat in men and women (p < 0.001). This underestimate increased in men with >24.6% body fat and women with >32% body fat (p < 0.001). Fat tissue mass in the trunk segment was overestimated by 2.1 kg (p < 0.001) in men and underestimated by 0.4 kg (p < 0.001) in women. BIA was also found to underestimate the fat free mass in the appendages by 1.0 kg (p < 0.001) in men and 0.9 kg (p < 0.001) in women. Compared to dual energy X-ray absorptiometry, bioelectrical impedance analysis underestimates the total body fat mass and overestimates fat free mass in healthy young adults."

and James Kreiger's excellent write up on bodyfat testing methods

I’ve heard people make the argument that, while BIA may not be that accurate, it should work fine when tracking change over time. The theory, they say, is that the error should be the same each time you use it.

The problem is that this isn’t true. As I mentioned in the article on hydrostatic weighing, the density and hydration of fat-free mass can change with weight loss. If this can affect the accuracy of hydrostatic weighing for measuring change over time, then you can be sure that the effect on BIA outcomes is going to be significantly larger.

Researchers have looked at the accuracy of BIA for tracking body fat change over time. In one study, the disagreement between BIA and the 4-compartment model ranged from -3.6% to 4.8% for measuring change. This means you could lose 3.6% body fat, but BIA would show no change. Or, BIA could tell you that you lost 8.8% body fat when you really only lost 4%. In fact, in this study, plain ol’ bod mass index (BMI) did just as well as BIA for predicting change in body fat, except for in one person.

BIA can be problematic because it’s a prediction based off of a prediction, so the error gets compounded. When you look at group averages for BIA measurements, there tends to be bias, with BIA often underpredicting how much fat you have. As with other techniques, the individual error rates can get high, with some research showing error rates of around 8-9%. In fact, BIA doesn’t do much better than BMI at predicting body fat in some cases. When it comes to measuring change over time, BIA can often underpredict the amount of fat loss, and the estimated change can be off by up to 8%.

Toddrific

Heh, I was going to say even if the scale is inaccurate it should be consistently so.

This is BF% calculator I'm sure it has a large variance.

http://www.fat2fitradio.com/tools/mbf/

weathergirl320

so basically you need an instrument to do it? because i saw a scale in the store ( just a normal bathroom scale) and it claimed to be able to measure body fat %. it seemed like a gimmick to me though.

It uses BIA...


Changes in body composition during weight loss in obese subjects in the NUGENOB study: comparison of bioelectrical impedance vs. dual-energy X-ray absorptiometry.

Verdich C et al. Diabetes Metab. 2011 Jun;37(3):222-9.

"RESULTS:

At baseline, BIA significantly overestimated FFM and underestimated FM (by 1-3 kg on average) compared with DXA, and the limits of agreement were wide (mean ± 7-8.5 kg). "


A comparison of dual energy X-ray absorptiometry and bioelectrical impedance analysis to measure total and segmental body composition in healthy young adults.

Lehy S et al. Eur J Appl Physiol. 2011 May 26

"BIA was found to underestimate the percentage total body fat in men and women (p < 0.001). This underestimate increased in men with >24.6% body fat and women with >32% body fat (p < 0.001). Fat tissue mass in the trunk segment was overestimated by 2.1 kg (p < 0.001) in men and underestimated by 0.4 kg (p < 0.001) in women. BIA was also found to underestimate the fat free mass in the appendages by 1.0 kg (p < 0.001) in men and 0.9 kg (p < 0.001) in women. Compared to dual energy X-ray absorptiometry, bioelectrical impedance analysis underestimates the total body fat mass and overestimates fat free mass in healthy young adults."

and James Kreiger's excellent write up on bodyfat testing methods

I’ve heard people make the argument that, while BIA may not be that accurate, it should work fine when tracking change over time. The theory, they say, is that the error should be the same each time you use it.

The problem is that this isn’t true. As I mentioned in the article on hydrostatic weighing, the density and hydration of fat-free mass can change with weight loss. If this can affect the accuracy of hydrostatic weighing for measuring change over time, then you can be sure that the effect on BIA outcomes is going to be significantly larger.

Researchers have looked at the accuracy of BIA for tracking body fat change over time. In one study, the disagreement between BIA and the 4-compartment model ranged from -3.6% to 4.8% for measuring change. This means you could lose 3.6% body fat, but BIA would show no change. Or, BIA could tell you that you lost 8.8% body fat when you really only lost 4%. In fact, in this study, plain ol’ bod mass index (BMI) did just as well as BIA for predicting change in body fat, except for in one person.

BIA can be problematic because it’s a prediction based off of a prediction, so the error gets compounded. When you look at group averages for BIA measurements, there tends to be bias, with BIA often underpredicting how much fat you have. As with other techniques, the individual error rates can get high, with some research showing error rates of around 8-9%. In fact, BIA doesn’t do much better than BMI at predicting body fat in some cases. When it comes to measuring change over time, BIA can often underpredict the amount of fat loss, and the estimated change can be off by up to 8%.

got it. thanks! so it seems to me that a lot of people on the message boards measure their %body fat. in general would they use BIA? or some of the other mentioned methods? whats the easiest and most accurate way to do it? and does body fat % really mean that much? or is it akin to BMI?

Toddrific

Many people suggest you keep your measurements instead of track your weight, as it more accurately reflects your body's change in body fat.

Acg67

got it. thanks! so it seems to me that a lot of people on the message boards measure their %body fat. in general would they use BIA? or some of the other mentioned methods? whats the easiest and most accurate way to do it? and does body fat % really mean that much? or is it akin to BMI?

My guess is most people get their bf% one of three ways; BIA, calipers or an online calculator that uses circumference measurements. The easiest and most accurate way would be to search for a DEXA scan (most places that cater to women have them) but it can be pricey, anywhere from $75-200. BF% is important, but I don't think you need a spot on number for most applications. BMI is not very accurate save for non athletic populations

ElPumaMex

bump, good links here !

weathergirl320

got it. thanks! so it seems to me that a lot of people on the message boards measure their %body fat. in general would they use BIA? or some of the other mentioned methods? whats the easiest and most accurate way to do it? and does body fat % really mean that much? or is it akin to BMI?

My guess is most people get their bf% one of three ways; BIA, calipers or an online calculator that uses circumference measurements. The easiest and most accurate way would be to search for a DEXA scan (most places that cater to women have them) but it can be pricey, anywhere from $75-200. BF% is important, but I don't think you need a spot on number for most applications. BMI is not very accurate save for non athletic populations

Thanks for the info and all the links. its not worth $75 to me lol. i dont really need to know THAT bad haha. thanks for all the great links!

Acg67

got it. thanks! so it seems to me that a lot of people on the message boards measure their %body fat. in general would they use BIA? or some of the other mentioned methods? whats the easiest and most accurate way to do it? and does body fat % really mean that much? or is it akin to BMI?

My guess is most people get their bf% one of three ways; BIA, calipers or an online calculator that uses circumference measurements. The easiest and most accurate way would be to search for a DEXA scan (most places that cater to women have them) but it can be pricey, anywhere from $75-200. BF% is important, but I don't think you need a spot on number for most applications. BMI is not very accurate save for non athletic populations

Thanks for the info and all the links. its not worth $75 to me lol. i dont really need to know THAT bad haha. thanks for all the great links!

You can also search for a BodPod which has some downsides but cheaper and relatively accurate, you can use google maps to find a location and see if they are close to you, should be around 30-40

mikesa3

I did the Bod Pod. You sit inside for 50 seconds 2x and it gives you body fat% and your resting metobolic rate. Mine was 40% 4 weeks ago but I hope it's lower when I go back in 2 weeks.
Nancy

HMVOL7409

I did the Bod Pod as well 3 weeks ago and have a follow up in 2 weeks, It was only $25 for us. Highly recommend if you can find one in your area.

mtnbiker1

Here is what I use. The brand is Omron:

http://www.google.com/products/catalog?hl=en&redir_esc=&client=ms-android-sprint-us&q=omron+body+fat+analyzer&v=133247963&um=1&ie=UTF-8&tbm=shop&cid=3436787771338165419&sa=X&ei=soeET4agGojgtgeNyciDCA&ved=0CKUBEPMCMAI#ps-sellers

You can see that it gets consistently high ratings/reviews. I think I paid about $30 for mine at GNC but it can be found for a little less. I've been using this kind for several years and its always been consistent.

Acg67

Here is what I use. The brand is Omron:

http://www.google.com/products/catalog?hl=en&redir_esc=&client=ms-android-sprint-us&q=omron+body+fat+analyzer&v=133247963&um=1&ie=UTF-8&tbm=shop&cid=3436787771338165419&sa=X&ei=soeET4agGojgtgeNyciDCA&ved=0CKUBEPMCMAI#ps-sellers

You can see that it gets consistently high ratings/reviews. I think I paid about $30 for mine at GNC but it can be found for a little less. I've been using this kind for several years and its always been consistent.

That's a BIA device and consistent doesn't mean accurate

Karabobarra

Bump

SirZee

Body fat % is the percentage of your body that is fat.

So if your body fat % is 33% and you weight 100lb, your body contains 33lb of fat and 67lb of other stuff (muscles, bone primarily).

Percentage of body fat is an indicator of fitness, a skinny person will in general have less body fat% than a very obese person.

HTH

lordsangel

its how much of your lean muscle mass is fat, men's are almost always lower due to a womans 7 layers and personally i think its so unfair but a healthy % for 20-39 yr old is between 21-33%.

jenalderman

bump for links

Leiki

The most accurate way to measure body fat is in an expensive apparatus most of us do not have access to.

http://www.bmi-calculator.net/body-fat-calculator/

This calculator will give you a rough estimate based on gender, and measurements of weight, waist, wrist, hips, and forearm.