Skin and bones
May 20, 2016 10:17 AM Subscribe
Is there any scientific way to determine the weight of bones in a body?
To head off the possible need to threadsit: I want to be clear that this question is not about ignoring the numbers on the scale, paying attention to how you feel, working out to gain muscle which is heavier than fat, or anything like that. It's not a cosmetic question.
Here goes: A person (let's call them, oh, potflour) loses weight through diet and also is diagnosed with osteoporosis. The rate of osteoporosis is very meticulously diagnosed in many parts of the skeleton.
The weight loss clearly involves fat and muscle and the body is smaller, but not as small as the low number on the scale would have indicated at a younger age.
So out of curiosity:
Is there any way to make a good estimation about how much of the weight loss was from the loss of bone density, and how much was due to flesh (fat and muscle) loss? How could you calculate something like this? Or is it impossible? How much do bones weigh anyway (on average) and how much mass do bones lose as they age anyway?
To head off the possible need to threadsit: I want to be clear that this question is not about ignoring the numbers on the scale, paying attention to how you feel, working out to gain muscle which is heavier than fat, or anything like that. It's not a cosmetic question.
Here goes: A person (let's call them, oh, potflour) loses weight through diet and also is diagnosed with osteoporosis. The rate of osteoporosis is very meticulously diagnosed in many parts of the skeleton.
The weight loss clearly involves fat and muscle and the body is smaller, but not as small as the low number on the scale would have indicated at a younger age.
So out of curiosity:
Is there any way to make a good estimation about how much of the weight loss was from the loss of bone density, and how much was due to flesh (fat and muscle) loss? How could you calculate something like this? Or is it impossible? How much do bones weigh anyway (on average) and how much mass do bones lose as they age anyway?
As a first approximation to get you started, check out this recent mefi post. You can plug in some basic info and it will make up a number for how much your bones weigh (see Section 3).
posted by ryanrs at 10:26 AM on May 20, 2016
posted by ryanrs at 10:26 AM on May 20, 2016
Yeah, this is exactly what a DEXA scan does.
posted by shelleycat at 10:31 AM on May 20, 2016
posted by shelleycat at 10:31 AM on May 20, 2016
Response by poster: Sorry to thread sit. I have a DEXA report in front of me. It doesn't have a BMC (it has a BMD for bone mineral density) but does not give results in terms of weight.
THe BBC site is fantastic ryanrs -- I learned the normal weight of my bones -- but I wonder how I can use the DEXA report to figure out how may pounds of my bones were lost. And if this info is there on the DEXA and I don't know how to read it, I'd appreciate illumination!
posted by flourpot at 10:39 AM on May 20, 2016
THe BBC site is fantastic ryanrs -- I learned the normal weight of my bones -- but I wonder how I can use the DEXA report to figure out how may pounds of my bones were lost. And if this info is there on the DEXA and I don't know how to read it, I'd appreciate illumination!
posted by flourpot at 10:39 AM on May 20, 2016
I'm not sure you're losing that much *weight* because the spaces left by the mineral loss aren't empty, they're filled with blood or bone marrow or something. So you would really be interested in the difference between the density of dry mineralized bone and bone marrow.
The mineral part of bone is fairly lightweight - about 15% of your body weight.
The parts of bones that are gone get filled in with blood and water.
posted by mskyle at 2:57 PM on May 20, 2016
The mineral part of bone is fairly lightweight - about 15% of your body weight.
The parts of bones that are gone get filled in with blood and water.
posted by mskyle at 2:57 PM on May 20, 2016
The total amount of calcium and phosphorus in the body, the primary component of bone mineral, is about 4 pounds. If you have severe osteoporosis with 25% bone mass density loss, then you are talking about roughly one pound. But as mskyle points out, some of this loss is replaced by water mass. So bone loss is almost insignificant in the total weight loss.
posted by JackFlash at 4:32 PM on May 20, 2016 [1 favorite]
posted by JackFlash at 4:32 PM on May 20, 2016 [1 favorite]
Also, if you're really just wondering why you're not as small as you would have been at x weight when you were younger. Less muscle mass is more likely than bone loss. Also, if you've lost a significant amount of weight your skin will be loser and you'll appear bigger than you did when you were originally that weight.
posted by missmagenta at 7:59 AM on May 21, 2016
posted by missmagenta at 7:59 AM on May 21, 2016
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posted by un petit cadeau at 10:24 AM on May 20, 2016 [2 favorites]