How To: Calculate Lean Body Mass, see if weightloss is fat
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Aaron_K123
Posts: 7,122 Member
Hey MFP. I've gotten a lot of great advice since joining the forum here a month ago and would like to try to pay it forward a bit. I'd say I'm a novice/beginner level in terms of weight loss and nutrition but I am an experienced geek when it comes to data collection and analysis. I've seen one topic come up repeatedly in the forums about whether or not you are gaining/losing muscle or gaining/losing fat when your weight changes. As it turns out if you take good measurements this is something that anyone can determine for themselves. I thought I'd try my hand at writing a quick guide/tutorial on how to do so. Expert-level types on weight loss and nutrition on this forum please let me know if I say something wrong here and I can correct it with an edit. I'd like to be able to refer to this post in the future since I get asked this a lot.
Okay so here we go. First lets define some terms:
Definitions
Body Fat Percentage (BF%): This is the percent of your bodyweight that comes from fat. If you weigh 100 pounds and are at 25% bodyfat that means that 25 pounds of you is fat.
Lean Body Mass (LBM). This is the weight of everything that comprises you that is not fat. That means muscle, but it also means water, bone, skin, hair, organs etc. When most people talk about changes in lean body mass they are thinking muscle but it is important to keep in mind water is a part of it as well.
So what are you going to need to do this? You need a scale, to measure your weight, and a method of measuring your bodyfat. The easiest most accessible method of bodyfat measurement is going to be a tape measurer or bodyfat calipers which you can buy online for about $15 US. In my examples I use both methods.
Taking your measurements
Alright lets get measuring. So first determine your weight with your scale. Whatever scale you use this should be the scale you continue to use throughout your measurements. Even if it is "wrong" it should be "wrong" the same amount everytime so its important for consistency to use the same scale. In my example I started my weight loss journey at around 175 pounds.
Now determine your percent bodyfat. Using a tape measurer measure your neck and your abdomen (around your navel) as well as your hips if you are female. Plug those numbers in along with your height and weight here to get your bodyfat percentage
http://www.machinehead-software.co.uk/bike/training/body_fat/body_fat_percentage.html
Using bodyfat calipers measure at 7-sites displayed here:
http://www.free-online-calculator-use.com/skin-fold-test.html
and plug it into the calculator here:
http://www.exrx.net/Calculators/BodyComp.html
There are different calculators out there these just happen to be the ones I have used.
In my example lets say I use the tape measure and determine my bodyfat is 22%.
Calculating your Lean Body Mass (LBM)
Okay we have our two numbers. 175 pounds and 22% bodyfat. Time to calculate. Simply multiply your percent bodyfat as a decimal to your scale weight, this will yield the weight of you that is fat. So 175 x 0.22 = 38.5 pounds of fat. Next subtract the pounds of fat from your scale weight, this is your LBM. 175-38.5 = 136.5 pounds. That's it, that is all there is to it. This tells you that at that time 38.5 pounds of me was fat and 136.5 pounds of me was everything else.
Determining if your weight loss is fat, muscle or water
This next part is the hard part. It requires that you take regular and consistent measurements over time. 3 years ago I worked hard to lose weight while maintaining my muscle. To ensure I was on the right track I weighed myself frequently with the scale and about every 3 weeks or so I measured my bodyfat and calculated my LBM both with a tape measurer and bodyfat calipers. Here is what I saw over a 8 month period.
So I was clearly losing weight and at a pretty steady pace. By fitting the data I determined I was losing 0.5 pounds per week. But was it all fat? Next lets look at bodyfat %
So I was clearly losing bodyfat as well. The tape measure and calipers gave somewhat different values but both showed a clear trend. Now for each of those points with my weight and my bodyfat percent I could calculate my LBM. So what did that look like?
Where both my weight and my bodyfat percent measures had a clear downward trend my LBM bounces up and down erratically but does not seem to change over time. The fluctuations are to be expected since if you recall water is part of your LBM and is responsible for all those fluctuations you see in your weight when you measure on the scale. Those fluctuations will be in the LBM measurement as well. The question is though over multiple measures is there a trend going up or a trend going down or no trend at all.
If you see a trend going up then congratulations you are gaining muscle. If you see a trend going down then this would suggest that in addition to losing fat you are also losing muscle and you can use the trend to calculate your rate of muscle loss. In this case you likely need to eat more and perhaps consider resistance or weight training to prevent muscle loss. If there is no trend at all like in my case that would mean that you are maintaining your muscle.
So in my experience from my measurements I determined that I lost 20 pounds, lost about 8% bodyfat and my lean body mass did not change suggesting that I maintained my muscle. During this time I was lifting weights regularly so this just goes to show in my personal experience even if you are losing weight gradually (0.5 pounds a month) and lifting weights you are unlikely to put on muscle while at caloric deficit.
I feel that taking stock of your LBM maybe once a month is a good idea as it can help you take stock of whether your weight loss is "all fat" as many people seem to assume, or if instead it is at least in part water (the random fluctuations) or muscle (a downward trend in LBM).
I know this became a very long post but I hope that at least some find it helpful
Cheers
Okay so here we go. First lets define some terms:
Definitions
Body Fat Percentage (BF%): This is the percent of your bodyweight that comes from fat. If you weigh 100 pounds and are at 25% bodyfat that means that 25 pounds of you is fat.
Lean Body Mass (LBM). This is the weight of everything that comprises you that is not fat. That means muscle, but it also means water, bone, skin, hair, organs etc. When most people talk about changes in lean body mass they are thinking muscle but it is important to keep in mind water is a part of it as well.
So what are you going to need to do this? You need a scale, to measure your weight, and a method of measuring your bodyfat. The easiest most accessible method of bodyfat measurement is going to be a tape measurer or bodyfat calipers which you can buy online for about $15 US. In my examples I use both methods.
Taking your measurements
Alright lets get measuring. So first determine your weight with your scale. Whatever scale you use this should be the scale you continue to use throughout your measurements. Even if it is "wrong" it should be "wrong" the same amount everytime so its important for consistency to use the same scale. In my example I started my weight loss journey at around 175 pounds.
Now determine your percent bodyfat. Using a tape measurer measure your neck and your abdomen (around your navel) as well as your hips if you are female. Plug those numbers in along with your height and weight here to get your bodyfat percentage
http://www.machinehead-software.co.uk/bike/training/body_fat/body_fat_percentage.html
Using bodyfat calipers measure at 7-sites displayed here:
http://www.free-online-calculator-use.com/skin-fold-test.html
and plug it into the calculator here:
http://www.exrx.net/Calculators/BodyComp.html
There are different calculators out there these just happen to be the ones I have used.
In my example lets say I use the tape measure and determine my bodyfat is 22%.
Calculating your Lean Body Mass (LBM)
Okay we have our two numbers. 175 pounds and 22% bodyfat. Time to calculate. Simply multiply your percent bodyfat as a decimal to your scale weight, this will yield the weight of you that is fat. So 175 x 0.22 = 38.5 pounds of fat. Next subtract the pounds of fat from your scale weight, this is your LBM. 175-38.5 = 136.5 pounds. That's it, that is all there is to it. This tells you that at that time 38.5 pounds of me was fat and 136.5 pounds of me was everything else.
Determining if your weight loss is fat, muscle or water
This next part is the hard part. It requires that you take regular and consistent measurements over time. 3 years ago I worked hard to lose weight while maintaining my muscle. To ensure I was on the right track I weighed myself frequently with the scale and about every 3 weeks or so I measured my bodyfat and calculated my LBM both with a tape measurer and bodyfat calipers. Here is what I saw over a 8 month period.
So I was clearly losing weight and at a pretty steady pace. By fitting the data I determined I was losing 0.5 pounds per week. But was it all fat? Next lets look at bodyfat %
So I was clearly losing bodyfat as well. The tape measure and calipers gave somewhat different values but both showed a clear trend. Now for each of those points with my weight and my bodyfat percent I could calculate my LBM. So what did that look like?
Where both my weight and my bodyfat percent measures had a clear downward trend my LBM bounces up and down erratically but does not seem to change over time. The fluctuations are to be expected since if you recall water is part of your LBM and is responsible for all those fluctuations you see in your weight when you measure on the scale. Those fluctuations will be in the LBM measurement as well. The question is though over multiple measures is there a trend going up or a trend going down or no trend at all.
If you see a trend going up then congratulations you are gaining muscle. If you see a trend going down then this would suggest that in addition to losing fat you are also losing muscle and you can use the trend to calculate your rate of muscle loss. In this case you likely need to eat more and perhaps consider resistance or weight training to prevent muscle loss. If there is no trend at all like in my case that would mean that you are maintaining your muscle.
So in my experience from my measurements I determined that I lost 20 pounds, lost about 8% bodyfat and my lean body mass did not change suggesting that I maintained my muscle. During this time I was lifting weights regularly so this just goes to show in my personal experience even if you are losing weight gradually (0.5 pounds a month) and lifting weights you are unlikely to put on muscle while at caloric deficit.
I feel that taking stock of your LBM maybe once a month is a good idea as it can help you take stock of whether your weight loss is "all fat" as many people seem to assume, or if instead it is at least in part water (the random fluctuations) or muscle (a downward trend in LBM).
I know this became a very long post but I hope that at least some find it helpful
Cheers
0
Replies
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You've outdone yourself with this post. It's really well-organized and informative.
More importantly though, people don't realize how CRUCIAL this part of switching to a healthier lifestyle is. They set themselves on a weight they want to be without considering body composition, and then they either get frustrated when the scale doesn't do what they want it to do or they get to their goal weight and still aren't happy with their appearances.
... Or worse, they get to a point where they are happy with their appearance but haven't reached that magic number on the scale they always hoped for, and they're disappointed after all that hard work!
Petition for everyone on this forum to focus more on their body composition!0 -
This is awesome - I went back and did the math - I had all my measurements and weights for the last couple months so I could use the tape measure method. I found out that I lost 14.31# of FAT but also gained about 6# of LBM. Which made me question the numbers since everyone says you can't gain muscle and lose fat at the same time - I'll attribute it to newbie gains and some water - but I know I didn't lose LBM cause the trend went UP!
My body fat % so far has gone from about 41% to 31% - This stuff is more important to me than the scale #. I can tell in my clothes and how I feel! It is great to have this information!0 -
This is awesome - I went back and did the math - I had all my measurements and weights for the last couple months so I could use the tape measure method. I found out that I lost 14.31# of FAT but also gained about 6# of LBM. Which made me question the numbers since everyone says you can't gain muscle and lose fat at the same time - I'll attribute it to newbie gains and some water - but I know I didn't lose LBM cause the trend went UP!
My body fat % so far has gone from about 41% to 31% - This stuff is more important to me than the scale #. I can tell in my clothes and how I feel! It is great to have this information!
41% to 31% is a huge improvement, congratulations. As for 6 pounds of lean body mass with a deficit I am a bit skeptical and it sounds like you are to. I am not sure how many data points you have (in terms of LBM) but it definately takes more than 2. You have to have a lot before you can be confident of a trend.
In my above graph I have something like 20 points but you will notice those points range from 132 pounds all the way to 139 pounds which is a 7 pound spread. If I just had the two measurements, 132 and 139, I might have thought that I had gained 7 pounds of LBM which would have been wrong.
The more points you have the more assured you can be that whatever trend you see is real and you figure out what your gain or loss is based on the fit of the trend rather than any two solitary points.
I didn't go into curve fitting, trendlines and evaluating trends because I thought that might be too math heavy.0 -
You've outdone yourself with this post. It's really well-organized and informative.
More importantly though, people don't realize how CRUCIAL this part of switching to a healthier lifestyle is. They set themselves on a weight they want to be without considering body composition, and then they either get frustrated when the scale doesn't do what they want it to do or they get to their goal weight and still aren't happy with their appearances.
... Or worse, they get to a point where they are happy with their appearance but haven't reached that magic number on the scale they always hoped for, and they're disappointed after all that hard work!
Petition for everyone on this forum to focus more on their body composition!
Thanks Otter, that means a lot to me truly and I agree people should be focused on their body comp not their scale weight if they want to improve their health.
Sadly I am a bit jaded with the forum in terms of informative posts. I do enjoy posting on the forum and reading others posts but I find most times good info quickly gets buried by "How can I lose 50 pounds in 2 weeks healthily?" and "Help I'm not losing weight and I eat 800 calories a day" posts and the spam of facepalms and lawl-cats that follows. Not that I'm judging, heck I take part in those as well. Just even if everyone agreed this was good info pretty sure it will still be buried in 3 hours.0 -
Added this post to my blog for future reference. It is better there anyways as the pictures don't get cropped so you can actually see the trend-line values.0
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This is awesome - I went back and did the math - I had all my measurements and weights for the last couple months so I could use the tape measure method. I found out that I lost 14.31# of FAT but also gained about 6# of LBM. Which made me question the numbers since everyone says you can't gain muscle and lose fat at the same time - I'll attribute it to newbie gains and some water - but I know I didn't lose LBM cause the trend went UP!
My body fat % so far has gone from about 41% to 31% - This stuff is more important to me than the scale #. I can tell in my clothes and how I feel! It is great to have this information!
41% to 31% is a huge improvement, congratulations. As for 6 pounds of lean body mass with a deficit I am a bit skeptical and it sounds like you are to. I am not sure how many data points you have (in terms of LBM) but it definately takes more than 2. You have to have a lot before you can be confident of a trend.
In my above graph I have something like 20 points but you will notice those points range from 132 pounds all the way to 139 pounds which is a 7 pound spread. If I just had the two measurements, 132 and 139, I might have thought that I had gained 7 pounds of LBM which would have been wrong.
The more points you have the more assured you can be that whatever trend you see is real and you figure out what your gain or loss is based on the fit of the trend rather than any two solitary points.
I didn't go into curve fitting, trendlines and evaluating trends because I thought that might be too math heavy.
I have the spread sheet at the office, so I'll have to look at the middle numbers when I get there tomorrow. Those were just the end points. I thought it was strange too - but there was a stretch there where I was probably eating closer to maintenance or better. No weight loss for a while. I was/am skeptical - but I kept redoing the number swearing I was using the calculator wrong!0 -
This is awesome - I went back and did the math - I had all my measurements and weights for the last couple months so I could use the tape measure method. I found out that I lost 14.31# of FAT but also gained about 6# of LBM. Which made me question the numbers since everyone says you can't gain muscle and lose fat at the same time - I'll attribute it to newbie gains and some water - but I know I didn't lose LBM cause the trend went UP!
My body fat % so far has gone from about 41% to 31% - This stuff is more important to me than the scale #. I can tell in my clothes and how I feel! It is great to have this information!
41% to 31% is a huge improvement, congratulations. As for 6 pounds of lean body mass with a deficit I am a bit skeptical and it sounds like you are to. I am not sure how many data points you have (in terms of LBM) but it definately takes more than 2. You have to have a lot before you can be confident of a trend.
In my above graph I have something like 20 points but you will notice those points range from 132 pounds all the way to 139 pounds which is a 7 pound spread. If I just had the two measurements, 132 and 139, I might have thought that I had gained 7 pounds of LBM which would have been wrong.
The more points you have the more assured you can be that whatever trend you see is real and you figure out what your gain or loss is based on the fit of the trend rather than any two solitary points.
I didn't go into curve fitting, trendlines and evaluating trends because I thought that might be too math heavy.
I have the spread sheet at the office, so I'll have to look at the middle numbers when I get there tomorrow. Those were just the end points. I thought it was strange too - but there was a stretch there where I was probably eating closer to maintenance or better. No weight loss for a while. I was/am skeptical - but I kept redoing the number swearing I was using the calculator wrong!
Yeah its more about fitting a trendline to a bunch of data and seeing if time correlates to gain or loss of LBM rather than look at only two points. Like I said if you look at my data the trend is clear that there is no change but if you picked any two points at random you might see either a big loss or a big gain of LBM on the scale of 7 pounds just because there is so much variation likely due to water fluctuation.0 -
Posting to return tomorrow to read through this all, thanks in advance for it!!0
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Does anyone know how to resize a picture in a post using the image codes? It cropped my graphs and cut out the r-squared values which I could bother to explain if they were visible.0
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Aaron great post, I first saw it on your blog. Tried to hit like and the dang tablet flashed it on/off. It was very informative and easy to follow.0
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Added this post to my blog for future reference. It is better there anyways as the pictures don't get cropped so you can actually see the trend-line values.
Make them smaller before putting them on the hosting site
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bump0
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this is great, thanks!0
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Bump0
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Very useful information. BUMP0
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Wondering how this got back on the mainpage seemingly at random but hey...thanks for the support guys I appreciate it and hope people find it useful.0
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Thanks Aaron! This is really clear and informative. I can't wait to have a few months of data!0
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