Lean Body Mass (LBM): Definition & Formula

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Question of the Week: What Is Lean Body Mass?

I’ve been getting a lot of questions recently about “Lean Body Mass”, so I thought it would be a good idea to address the concept in more depth so you can understand exactly what it is, why it’s important, and how to calculate it.

Definition: What is Lean Body Mass (aka LBM)?

Simply put, lean body mass is comprised of everything in your body besides body fat.1 Your lean body mass includes:
Lean Body Mass
…and anything else in our bodies that has mass and is not fat.

As an aside, for the average adult male about 42% of body weight is skeletal muscle and it’s about 35% for females.

Lean Body Mass Formula:

Lean Body Mass = Body Weight – (Body Weight x Body Fat %)

This equation is taking your body weight in pounds and subtracting it from the amount of fat you have in your body in terms of pounds.  Simple.  If you don’t know how to measure your body fat, here are 5 Ways to Measure Body Fat.

Beware of some of the calculators online that attempt to arrive at your lean body mass without knowing your body fat percentage first.  These calculators attempt to calculate your lean body mass based on your height, weight, age, and/or sex, which will most likely be completely inaccurate.

Why Is Knowing Your Lean Body Mass Important?

Most people rely 100% on the weight scale when attempting to track changes in body fat.  While I do strongly recommend Monday Morning Weigh Ins during a fat loss program (and even after) as a proxy for fat loss, tracking body fat directly and tracking LBM is helpful to make sure you are losing only fat and no muscle.  Losing muscle is highly undesirable because your metabolism will decrease and aesthetically, you may not look leaner even if you do lose weight.

Lean body mass is also your set point to determine how much fat you should lose and what your body fat percentage will be if you lose a certain amount of fat.  You can check out the Ideal Body Weight Formula, which takes into account your lean body mass to arrive at your ideal weight.

If you would like to learn more about losing fat without losing muscle, I highly recommend checking out my free Get Lean Guide.

I hope this was helpful.  Let me know if you have any questions, or have anything to add by leaving a comment.

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35 Comments on “Lean Body Mass (LBM): Definition & Formula

  1. Marc Perry
    August 25, 2011 #

    Have any questions for me? I may make it into a Question of the Week!

    1. Jocelyn
      June 16, 2012 #

      I have a question. I have calculated an ideal weight using my lean body mass and a “normal weight” BMI 0f 18-20%. When I lose weight will my lean body mass go down?

      1. June 18, 2012 #

        @Jocelyn – the idea is that you want to keep your LBM the same as you lose weight. Your LBM may go down a little bit as you may be retaining water, but generally, in order to get leaner the idea is to lose fat without decreasing your LBM. I suggest checking out my Get Lean Guide for more information – http://www.builtlean.com/getlean/

  2. mary
    August 25, 2011 #

    Do you have any suggestions on how to reduce cellulite? I understand that it is body fat, but why is it so difficult to reduce this unsightly fat? Men do not seem to have this problem. Thank you.

    1. Marc Perry
      August 25, 2011 #

      @Mary – That is a simple question with a not so easy answer. Women have hormones in different amounts then men, which can significantly effect fat loss. So the short answer of why it’s harder for women to lose fat than men is hormones. I will certainly address this in much more detail in a future post, so thanks for the question. Regarding the cellulite, as I understand it (I’m not an expert on cellulite by any means and don’t know too much about it), but it’s really just a matter of losing as much fat as possible without losing muscle. That’s really it.

  3. dave stein
    August 25, 2011 #

    I have been using the hand held machine to calculate my body fat. Each time it comes up around 21% ( 63 yro male)
    Recently I had a trainer calculate it by stepping on a scale and plugging in some numbers,( weight,ht. age sex). It came up each time at 6%
    so something is not right. Could I be squeezing that machine to hard?
    What part of your body to you use the caliper?
    Thanks, Dave

    1. Marc Perry
      August 25, 2011 #

      @dave stein – I’m surprised at such a large discrepancy. That’s the challenge with measuring body fat is that it’s never a true measurement, only an estimate based on some algorithm created over 50 years ago. I would go with the caliper method and measure body fat in 3 or more places. For more on the various methods of body fat measurement, check out this article: 5 Ways to Measure Body Fat Percentage. If you want the most accurate estimate, it may be worth trying out a DEXA machine in your area…but being able to track body fat over time with a caliper I still think is the way to go.

  4. dave stein
    August 26, 2011 #

    at 140 lbs,5′ 6,which do you think is more accurate. pro athletes in their prime probably are closer to the 6%, i think. just got back from arthroscopic on my menisci. any suggestions for quicker recovery than normal?

    thanks for your speedy reply. good job.

    1. Marc Perry
      August 27, 2011 #

      @dave stein – If I was able to see you in person, I think I could give you a decent estimate of your body fat percentage. My guess is your body fat is somewhere in the middle between the high estimate and the low estimate. If you have 6% body fat, then you will have veins going across your stomach and in your shoulders and legs that are visible. 6% is extremely lean for a guy above 40 years old. I wish I could help you with recovery ideas, but I really don’t have any that are specific to that surgery. I hope you have a speedy recovery.

  5. Alexander
    August 27, 2011 #

    Hi, Marc
    Just wanted to share with you an update of what I’ve been accomplishing. It’s been only a month since I read your Get Lean Guide and many of your advices published in your web site. With all that motivation, I started a calorie deficit diet together with strength exercises and some HIIT.

    In this month I have allready dropped 8lbs, taking my body fat percentage from 18.35% to 14.85%. In the process, I have only lost 0.72lbs of LBM, but lost 7.28lbs of fat. I’m working to get get my body fat percentage to 10% or less. I just wanted you to know that I never got such good results before in such a short time. I really thank you for all the good information and wisdom you share with us. It’s the best thing I’ve found on fitness in the web. You’re the best!

    1. Marc Perry
      August 30, 2011 #

      @Alexander – That’s absolutely fantastic! Love hearing success stories. Keep up the great work and thanks for keeping me posted.

  6. Anonymous
    September 5, 2011 #

    Wow. This gave me a whole new way to look at it.
    I’ve known about lbm for a while, but not like this.
    From now on I will take lbm way more into consideration.

    Thanks for this

  7. Dee
    November 17, 2011 #

    I am a 35 year old female. I have been consistently working out with weights (lifting heavy) and cardio (moderate and HIIT) for several months. I don’t take much stock in the scale or my handheld fat monitor since neither have moved much in the past 4 months -but I know I am losing fat and gaining muscle. I decided to use the BodPod every so often to assess my body fat and get a more accurate gauge of my progress. Here are my stats:

    BodPod assessment #1:

    193.9 lbs body weight
    47.2% body fat
    91.6 lbs fat weight
    102.3 lbs lean weight

    BodPod #2- 4 weeks later:

    195.1 lbs body weight
    43.3% body fat
    84.5 lbs fat weight
    110.6 lbs lean weight

    I am perplexed by the lean weight. I know it includes everything with mass in the body except fat and I’m certain some of it is muscle but I know its not possible to gain 8 lbs of muscle in 4 weeks. What could be accounting for the increase in lean weight? (Not that it matters, I’m pleased with the results)

    BTW, you’re “share with friends” widget makes it very difficult to post.

    Thanks in advabce

    1. Marc Perry
      November 17, 2011 #

      @Dee – Thanks for sharing your stats. I do think it’s very possible to gain 8lb of muscle in a month, particularly for someone who has not lifted weight in a while. It’s unlikely, but it does happen. My guess is your LBM will plateau and you will start losing only fat assuming you are eating less calories than you are burning. Also, if you could please elaborate on what you mean by the “share with friends” widget make it very difficult to post, I would appreciate it!

  8. dee
    November 17, 2011 #

    Marc, thanks for the response. When I posted earlier there ws a widget popopping up in the spot where I ws typing it was ohne of those tht wld allow me to post to facebook, twitter, etc. However as I type this on my phone I don’t see it so perhaps the issue was with the pc I was on. Thanks.

    1. Marc Perry
      November 20, 2011 #

      @dee- thanks for letting me know. I’m seeing a little bit of an issue with my site performance/display in internet explorer, so need to get that figure out!

  9. Heather
    April 5, 2012 #

    I ran up on your site b/c I was looking into what is a healthy percentage of body fat. I’m 35 yrs old 5 ft 7.25inches I weigh 124 pounds. I work out 4 days a week for 2 1/2 hours. I love to workout however. I however don’t know that I care for all the veins that keep popping out. At the gym the weigh your percentage by a scale with impulses (or something like that). 5 months ago I weighed 124 and was 16.9% body fat. Now I am still 124 but 13.9%. That is like .6% a month. Is that normal? I don’t want to be unhealthy or cause issues by working out, I just love to do it. Do you have any suggestions? Where do I draw the line? I have all kinds of veins in my arms that stick out, one that is next to my appendix scar and one on my knee. However, their is one that you can feel in my leg but I can’t yet see it. All though, they look cool at the gym not so much in a pretty dress.
    Please let me know if you have any insite you can give me. THANKS

    1. April 8, 2012 #

      @Heather – sounds like you are very lean. I would say draw the line at 14-15%, where you are now. The issue is that getting any leaner can affect your menstrual cycle etc. Women need at least some fat for hormones to function properly. It does sounds like you’ve reached quite an impressive fitness level, so kudos to you!

  10. Heather
    April 9, 2012 #

    Marc,
    Thanks for responding. I appreciate the help, but how do I just stop working out? I don’t want to stop! However, I don’t want to be unhealthy either. Isn’t their a way to continue to work out, but not lose any more fat?
    According to my Polar I burn anywhere from 900-1250 each time I work out. On an average day I eat around 1500 calories. I can’t really eat much more than that, unless I eat unhealthy calories.
    I really would like to continue to gain Lean Muscle ( I don’t want to be real bulky) without losing anymore body fat. Is that possible? If so, how?
    Again, thanks for getting back to me.

    1. April 15, 2012 #

      Hi Heather, I never said stop working out, I just said to be careful with your body fat percentage because getting too lean is a problem particularly for women. I would suggest eating more healthy fats like olive oil, almond butter, and consider starchy carbs sources like rice and sweet potatoes. It makes it a lot easier to increase your calorie intake, which if I were you would be my focus. For someone as active as yourself with your body stats, 2000 calories could work completely fine without gaining any fat. You can monitor your weight of course. You may even be able to gain a little muscle. The idea is that you need to eat more calories than you burn to gain muscle.

  11. kathie
    May 30, 2012 #

    Hi Marc
    I see all kinds of information about bodyfat%, but so far have been unable to find any indication of what a healthy lbm weight would be for my height. the reason this is important to me is that I am trying to figure out whether i just need to shed some more fat and accept my lbm as it is, or build up more muscle.
    my lbm on my tanita fluctuates from around 46kg to 49kg (101-108lb)and I am 176cm 5’9.5″tall
    two years ago I successfully shed around 18kgs (40lbs) and my lbm stayed pretty much the same, so I lost purely fat. However my bf is still too high, although my weight is ok. Do you think my goal should be to build more muscle? or just shed more weight/fat. Or if you could direct me to any sites that talk about lbm or have lmb charts that would be fantastic. Thanks!

    1. June 3, 2012 #

      @kathie – over the years, I’ve done body fat assessments on many women and I can tell you that somewhere around 110lb would be more ideal for a women your height. With that said, 100lb is still a solid level. I would say anything underneath that level would be too little. This is just from my experience and LBM is a little tricky because some people have bigger and heavier bones than others. The other thing you can do is measure your body parts like your legs, arms, waist and see what they are. For example, if your thighs are much less than 19 inches, that’s pretty thin. Finally, you could even think of your LBM in terms of strength. I plan on creating an awesome post that will show the various body fat percentages, weight, and measurements of various men and women. I plan on doing this in the next three months, so if you haven’t signed up on our email list yet, I would do that: http://www.builtlean.com/email/. Sorry I could not give you something more specific, but non of this is an exact science.

      1. Abhisaar
        July 30, 2012 #

        HI marc…i am skinny guy and my weight is 45 and i workout gym last year and 2-3mnths ago i took whey gold standard protein and now i took lean body mass 60 and is it good for me without any cause of problem? Please help marc…thank you!

      2. August 2, 2012 #

        @Abhisaar – I would check out this article on Whey Protein. In my opinion, protein supplements are 100% not necessary to get you the results you want, they can however be convenient for some people are have trouble eating enough protein from whole food sources.

  12. kathie
    June 3, 2012 #

    First of all Marc, Thanks so much for taking the time to respond to me personally. I have pretty big legs from doing a lot of cycling. they are 20″. However my Tanita segment scale tells me that (strangely) one of my legs is overfat. I think its my left.

    But seriously, my plan now is going to be to get my lbm up to over 110 on a continuous basis (the tanita goes up and down, but it does show trends) and at the same time I’m going to drop another 3kgs of fat in the coming months. I’m looking forward to reading your newsletter. BTW, i posted a similar question on the facebook page of cutthefatpodcast and got a completely different answer to the one I was looking for, but certainly really interesting.

    https://cutthefatpodcast.com/1354/cut-the-fat-blog/exercise-and-fat-loss/do-you-have-enough-muscle-how-to-know

    I guess in the end its all about building strength so that you can do other stuff and not simply for the sake of having a certaing lbm.

    Thanks again!
    Kathie

  13. Abhisaar
    August 3, 2012 #

    Dear marc..i agree ur commentd but i eat whole food and everything cuz i am pure veggie not non-veg as i cant egg too…i eat sandwich,cheese,vegetables,milk and many more as i was 42kgs and now almost 45.5kgs :) and i workout hard so need to drink protein shake after workout to gain weight and muscle gain…so took lean body mass 60 as trainer said and spoke to doctor also before i take this protein he said i can have it….:) so wad u think marc and can you tell me is dat okay or if not then plz tell me..i wuld really thank you for ur help…wich is good protein shake for me after workout to gain muscle and weight and protein shake i cant drink egg u knw :)…thank! Waiting for ur reply

    1. August 9, 2012 #

      @Abhisaar – We don’t have any articles on protein shakes at this time, but you can check out this article on Whey Protein, which has some whey protein recommendations.

  14. Moo
    September 10, 2012 #

    Hi Marc. I am female, 5.6, 288 pounds, 40.9 body fat (on two scales). My lean body mass sounds too much? I use to be 120. Does the water count in it? I am always dehydrated. And how to know that I’m losing body fat? If my lean body mass doesn’t change that’s good, right? Thanks.

    1. September 12, 2012 #

      @Moo – Because your body fat is relatively high, it’s a lot more difficult to measure and track lean body mass. If I were you, I wouldn’t track LBM, I would track your weight instead as a proxy for fat loss. As long as you are doing some resistance training and eating ample protein, let’s say 100 grams per day, you shouldn’t lose any muscle. In addition, those who have more fat to lose will generally lose little muscle on larger calorie deficits because your body will readily use body fat stores.

  15. Alvin
    October 3, 2012 #

    I’ve been lifting weights for two years consistently now. I’m 240 lbs. with 20-22% body fat. If I were to drop 20 pounds of purely fat, would it be possible to do it without losing any muscle that I’ve built? Or does losing that kind of weight always correlate with at least some muscle loss at the expense of time (“the faster you lose fat the more you’ll lose muscle – idea”). I’ve taken a nutrition class and understand how macros and caloric deficits work. Thank you for your time.

    1. October 4, 2012 #

      @Alvin – That’s a great question. From my own experience with my training clients, I never had one client lose an ounce of muscle while losing fat (well actually one who tried a very low carb diet when he was already lean). This is because they did intense strength training, did not go too low on the calorie deficit, and ate sufficient protein (roughly 0.8grams per pound of body weight). I think if you follow these 3 guidelines, you can keep the vast majority of your muscle mass. As you start getting around 10-12% body fat, it’s very possible that you lose a little muscle mass. So let’s say a bodybuilder looking to get shredded for competition may lose 3-5lb of muscle as he strips his body of all the fat he can.

  16. Lisa
    October 4, 2012 #

    Hi
    Why is it that calculating lean body mass and ideal body fat ratios using your guide generally results in target weight lower than other recommended guides? Should height be considered and age? Thanks

    1. October 4, 2012 #

      @Lisa- WHat “other recommended guides” are you using? For example, I weight 170lb and I’m 5’11”. According to the BMI Index for my height, a “normal” weight range would be from 133 to 179 pounds. Also, keep in mind the ideal body weight formula is individual specific. A better barometer of over health may be the waist to height ratio, which is a relatively new metric that research has shown may be better than the BMI Index.

      Best,
      Marc

  17. Ashraff
    October 6, 2012 #

    hi, i have weight around 110kg’s..is it recommended to drink the weight body mass product because i exercise almost everyday and intending to build up my muscle and loosing fat..please help me,im clueless

    1. October 11, 2012 #

      @Ashraff – I highly suggest signing up for our weekly newsletter and reading over the Get Lean Guide.

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