Accuracy of body fat calculations?
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Well then, in that sense, a rational person would realize that for the $40 cost of DEXA scan, they could afford 1,371 grams of whey protein, which over a 6 month span works out to 7 grams to pad their protein estimates. And now they didn't have to spend 10 minutes inside of a medical device.
I'm not entirely sure how to answer that other than to say that I literally do not see a real use for it. The only thing I can think to do with it is to plug it into a calorie calculator to help get an estimate of how many calories to eat but I can just as easily figure out that calorie level based on my experience tracking my food.
Not everyone logs, some do not log accurately, and even some don't have the common sense to figure out when they are overeating based on the scale not moving down.
Knowing bodyfat % also helps a person to accurately gauge lean body mass. And I see a lot of people like using LBM to calculate their macros on here.
Why you always gotta make it weird bro?0 -
Perhaps it's not something worth worrying about as long as I know that I am eating well and working out to be the best I can be.
That's what I would do personally. If you feel good, look good, perform well and are happy then the actual number is largely secondary. It never hurts to have data and trends but don't let it become a distraction.
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From the articleNone of them are particularly accurate although some have better prediction rates than others.
If you want a good overview read all the parts to this series:
The pitfalls of body fat measurement
From the article:When a weather man gives you a forecast, he doesn't measure the weather. He is predicting the weather. And that's exactly what is happening when you have your body fat tested. We are predicting your body fat levels, not measuring them. Along with that prediction comes a certain amount of error. Just as the weatherman cannot predict the weather with 100% accuracy, we cannot predict your body fat levels with 100% accuracy. In fact, we can't even predict your body fat with 70% accuracy. In this article, you are about to learn just how bad the prediction really is.
See, I've said a similar thing, but lately I've wondered how true that even is. If we dissect a body, we still end up not measuring visceral fat very well. Fat molecules exist inside of organs and muscle tissue for use as fuel or for generating certain hormones. This is one area where DEXA scanners are a bit different than our expectations - calipers and hydrostatic weighing use measurements take on such dissected corpses to come up with models. A DEXA scan can potentially pick up fat inside those areas that would be ignored by dissection. So I'm not sure even dissection is accurate. It really requires having a true idea of what we intend to mean by the term body fat.The only way to truly measure your body fat is through carcass analysis. That means you would have to be dead so that we could strip all of the fat off of your body and weigh it. I don't see anybody volunteering for that any time soon.0 -
I'm not entirely sure how to answer that other than to say that I literally do not see a real use for it. The only thing I can think to do with it is to plug it into a calorie calculator to help get an estimate of how many calories to eat but I can just as easily figure out that calorie level based on my experience tracking my food.
Not everyone logs, some do not log accurately, and even some don't have the common sense to figure out when they are overeating based on the scale not moving down.
Knowing bodyfat % also helps a person to accurately gauge lean body mass. And I see a lot of people like using LBM to calculate their macros on here.
First I'll point out that I am answering these questions from my point of view. I don't find bf% useful for me. I log. I log extremely accurately. I also base my macros on my full bodyweight, not on LBM. So again, bf isn't a useful number for me. Interesting, yes. Useful, no.
That being said, macro calculations are best estimates and just as often based on full bodyweight, not LBM (i.e., .8g/pound protein, .45g/pound fat, balance comes from whatever combo of carbs/protein/fat, etc.) Even the protein figure is much debated, ranging from .62g-1.5 g and may be based on full bodyweight or LBM. Knowing that I am 25% fat or 32% fat isn't really going to change them too much. If I decided to eat 1g of fat per pound of LBM, I could just as easily look up what an average size woman's body fat percentage is (25%-31%) and use that to determine my protein. I'm 149 lbs and that would give me a range of 103-112g protein. The 9g variance isn't enough to make much of a difference IMO so the fact that I'm not sure exactly where I land between 25% and 31% isn't a big deal. I could even go over to my neighbor Senecarr's house to borrow a scoop of protein to make that up each day.
I'm not sure what your point about not logging or logging inaccurately is meant to address. How does a bf% help a person who doesn't log, logs inaccurately, etc.?0 -
From the articleNone of them are particularly accurate although some have better prediction rates than others.
If you want a good overview read all the parts to this series:
The pitfalls of body fat measurement
From the article:When a weather man gives you a forecast, he doesn't measure the weather. He is predicting the weather. And that's exactly what is happening when you have your body fat tested. We are predicting your body fat levels, not measuring them. Along with that prediction comes a certain amount of error. Just as the weatherman cannot predict the weather with 100% accuracy, we cannot predict your body fat levels with 100% accuracy. In fact, we can't even predict your body fat with 70% accuracy. In this article, you are about to learn just how bad the prediction really is.
See, I've said a similar thing, but lately I've wondered how true that even is. If we dissect a body, we still end up not measuring visceral fat very well. Fat molecules exist inside of organs and muscle tissue for use as fuel or for generating certain hormones. This is one area where DEXA scanners are a bit different than our expectations - calipers and hydrostatic weighing use measurements take on such dissected corpses to come up with models. A DEXA scan can potentially pick up fat inside those areas that would be ignored by dissection. So I'm not sure even dissection is accurate. It really requires having a true idea of what we intend to mean by the term body fat.The only way to truly measure your body fat is through carcass analysis. That means you would have to be dead so that we could strip all of the fat off of your body and weigh it. I don't see anybody volunteering for that any time soon.
I hadn't thought of that but yes, that is a valid observation.
I guess it does support the point that people shouldn't get too caught up with actual numbers.
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I'm not entirely sure how to answer that other than to say that I literally do not see a real use for it. The only thing I can think to do with it is to plug it into a calorie calculator to help get an estimate of how many calories to eat but I can just as easily figure out that calorie level based on my experience tracking my food.
Not everyone logs, some do not log accurately, and even some don't have the common sense to figure out when they are overeating based on the scale not moving down.
Knowing bodyfat % also helps a person to accurately gauge lean body mass. And I see a lot of people like using LBM to calculate their macros on here.
First I'll point out that I am answering these questions from my point of view. I don't find bf% useful for me. I log. I log extremely accurately. I also base my macros on my full bodyweight, not on LBM. So again, bf isn't a useful number for me. Interesting, yes. Useful, no.
That being said, macro calculations are best estimates and just as often based on full bodyweight, not LBM (i.e., .8g/pound protein, .45g/pound fat, balance comes from whatever combo of carbs/protein/fat, etc.) Even the protein figure is much debated, ranging from .62g-1.5 g and may be based on full bodyweight or LBM. Knowing that I am 25% fat or 32% fat isn't really going to change them too much. If I decided to eat 1g of fat per pound of LBM, I could just as easily look up what an average size woman's body fat percentage is (25%-31%) and use that to determine my protein. I'm 149 lbs and that would give me a range of 103-112g protein. The 9g variance isn't enough to make much of a difference IMO so the fact that I'm not sure exactly where I land between 25% and 31% isn't a big deal.
You seem to have a good grasp on things then. I also go by bodyweight and the ranges you offered seem legit. I am a proponent of offering macros ranges vs. giving a hard figure.0 -
Well if the Dexa scan estimated that lady at 25.7% BF,...i certainly won't be getting a Dexa scan done anytime soon then.
That's astonishing!0 -
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I do think many of the BF% options are pretty inaccurate, but I do think they can show a trend. When I do my weekly or monthly weigh-ins....I do have my scale do the BF% along with the weight. I know it isn't accurate, however I want to see the trend. That at least gives me some usable information. I know that measurement is even more inaccurate than the DEXA scan, but it's free....so I use the info it gives me.
I also use my eyes and take a real critical look at how my body is changing. If I had to give myself a rough estimate, I'd say I am about 25% BF. However I also think that doesn't have all that much meaning to me in my day to day life. I have some pockets of fat I'd love to blast off...and that'll be my focus in my upcoming long *kitten* recomp, but I am not aiming for a particular BF%, etc.
Nice. I like this trend idea too.
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Yeah, ultimately for most people, I'd agree with the go by how you feel about what is in the mirror approach. I've had a DEXA scan in June, and will probably do one again in December (the place I has a minimum of six month wait between scans, which is also decent timing to me), but I'm a numbers/statistics interested person, and I have a poor sense of aesthetics to go by the mirror.
Sorry.
I don't think you can judge really well based on your photos because they show such a small portion of your body. We all carry fat differently. I could take a picture of myself that looked like the 20-22% woman but the truth is that under my waistline I have a sizable hidden roll of fat that takes me well above that percentage.
I saved a few links to pictures of women who had DEXA scans to figure out their bf%. Here they are.
When comparing those people's measurements, it is worth noting that DEXA scans usually register 3% higher than most traditional caliper methods. This may have to do with DEXA is going to detect visceral fat a lot more because it is an x-ray. The 25.7% woman from your link looks more like she's between the BUILTLEAN picture's 15-17% and 20-22%.
Agreed.
I think that body fat % is interesting because it is a number but I don't think that it is a very useful number.
I'll admit that even though I think the number isn't too useful I would like a DEXA scan done too. I can get a two visit package for $70 (one visit $40), which isn't bad at all. The info on how my fat is distributed interests me. I am very uneven/disproportionate from what I see in the mirror. Nobody (or at least very few people) is completely proportional, of course, but that's the part that interests me the most.
I had it for similar reasons, and just because I'm a data geek and was curious. Also I was interested in bone density and tend to hold weight around the middle, so wanted to make sure I didn't have excessive visceral fat. I'm glad I did it and will likely do a follow up at some point.0 -
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