Measuring Body Fat Percentage & Measuring Muscle Mass Percentage | Not Your Average Fitness Tips

Measuring Body Fat Percentage & Measuring Muscle Mass Percentage

As you get leaner, one of the biggest challenges is measuring body fat percentage and measuring muscle mass percentage.  If you’re trying to lose a lot of weight, the scale is just as good a tool as any.  However, when you’re trying to lose the last 5-10lbs of fat while preventing muscle loss, the scale alone won’t necessarily help.  How can you effectively measure your weight loss results if you don’t know your body fat percentage or muscle mass percentage?  Based my recent experience, your best bet is to combine a variety of different methods.  Even then, it’s tough to definitively determine anything in the short term.


Measuring Body Fat & Muscle Mass

I recently finished doing Joel Marion’s Xtreme Fat Loss Diet.  While I’ll be reviewing that program separately, I thought I’d highlight how I tracked my results.  First thing to note, this was an experiment and I would not advise taking your weight, measuring body fat percentage, and measuring muscle mass percentage every day.  As you can tell from the graph above, the fluctuations are mind boggling and can cause even the sanest person to go crazy.  Regardless, I’m pleased with the overall results and achieved my goal of losing a lot of fat with little to no muscle loss.  The same methods that I list below can be used to determine if you’re gaining muscle with little to no fat gain as well.

Measuring Body Fat Percentage

I’m always concerned about how much fat I’ve gained or lost from a diet or exercise program.  I’ve written about Best Ways to Measure Body Fat Percentage before, but I’d like to revisit some of those methods and show how they can be combined with other methods to give you a clearer picture of how successful your routine is.

Scale (Weight Loss): starting from a relatively lean weight, I lost almost 9lbs in 24 days using the Xtreme Fat Loss Diet.  That on its own may sound impressive, but what if it was just water weight?  Worse, what if it was muscle loss?  The scale is a great starting point in determining how effective a routine is but isn’t an end point.  In general, if you use weight loss in conjunction with some of the methods that measure muscle mass percentage below, you’d have a reasonably good idea if you’re on track.

Body Fat Percentage (Fat Loss): I lost nearly 8lbs of fat over the last 3+ weeks.  This is very important to me.  However, how accurate is this measurement?  Body fat testers are notoriously inaccurate.  Skinfold calipers can be useful but if you’re not experienced, you won’t achieve consistent results.  Plus, as you get leaner, a difference of a few millimeters can mean the difference between 8% and 10% body fat.

Body fat testers that send a weak electrical signal through your body are nice in theory but some shortfalls include fluctuations due to hydration levels, when you last ate or exercised, and even the angle you hold the equipment at.  Unless you’re getting professionally tested, the best you can do is use a bioelectrical impedance body fat tester first thing in the morning.  This should lead to more consistent results.  Be cognizant that your body fat could vary significant based on whether you cheated or fasted the day before.

Measuring Muscle Mass Percentage

When it comes to weight loss, ensuring that you don’t lose muscle is just as important as maximizing fat loss.  Once again, there are a few different alternatives, none perfect.

Strength: if you’re lifting the same or more weight from workout to workout, you are almost certainly not losing any muscle mass.  If your lifts start to decline, then there could be a concern that you’re losing muscle.  One caveat, if you do bodyweight training, doing the same number of reps for an exercise may not indicate that you are preserving muscle mass.  If fat loss is your goal, your body will be declining in weight making it easier to do bodyweight exercises.  Therefore you end up doing the same number of reps at a lower weight meaning you might be losing strength and thus losing muscle mass.

Skeletal Muscle: the problem with just taking your weight and measuring body fat percentage is that you might think you’re losing muscle when you’re not.  Extreme example, if you go from 200lbs at 10% body fat to 180lbs at 10% body fat, it looks like you only lost 2lbs of fat and 18lbs of muscle.  The problem is that you are also losing water weight.

Lean muscle is made up of organs, bone, and skeletal muscle.  Skeletal muscle is really the only thing you can control.  When you perform resistance training, skeletal muscle increases.  How do you measure skeletal muscle?  Using the same electrical current that you use to measure body fat percentage.  That’s the number I show in the graph at the top of the page.  You can see that my skeletal muscle fluctuated by 2lbs, well within the margin of error for this method.

Ultimately, when measuring muscle mass percentage, skeletal muscle is what I deem most important.  Based on my body fat tester, I lost little to no skeletal muscle.  This is consistent with my resistance training results since I didn’t decline in any of my lifts.

Measuring Overall Appearance

If you’re measuring body fat percentage and measuring muscle mass percentage, what would you really like to see?  If you’re like me, the answer is a better looking body when you look in the mirror.  I’ve never been a huge fan of this method because every mirror is different.  Plus, I can always identify flaws in my body that I’d like to improve.  I also have a short term memory so it’s tough to remember what I looked like a few days or weeks ago.

For that reason, a lot of people take before and after pictures.  This is an excellent approach provided that you take the picture in the same place and same pose.  Otherwise you can easily manipulate what you look like in a photo.  Just make sure you’re honest with yourself.

Finally, I like the simple tape measure method.  When I’m on a fat loss diet, I’m happy as long as my shoulders stay the same width and my waist is declining.  This approach isn’t without its flaws since it’s hard to take accurate measurements, especially day to day.  Over the long term, I think this is highly effective though.  This can be done in conjunction with assessing how well your clothes fit.

Final Thoughts

Ultimately it’s hard to effectively measure body fat percentage and muscle mass percentage.  This makes evaluating short term results incredibly difficult.  However, if you combine a few methods above, you can get a reasonably good idea of how your body is changing.  Consistency is key; otherwise, the results will vary significantly.  For beginners, measure your weight loss with a standard scale.  Combined with making sure that your lifts are not declining should ensure that you’re losing fat and not muscle.  For a more advanced approach, start measuring body fat percentage and measuring muscle mass percentage (skeletal muscle).  Evaluate your final results based on how your overall appearance changes.  Nothing is perfect, but the more methods you combine, the more confident you can be that you are achieving your goals.

26 Responses to “Measuring Body Fat Percentage & Measuring Muscle Mass Percentage”

  • I tried all that but decided the best way as suggested by Tim Ferris is to simply look in the mirror and compare against previous photos of yourself or others … I read all the time people quoting ridiculous low bodyfat% and when you see their photo … I think “they need to stop jerking off” … To me I don’t even look for the 6 pack any more it’s more how visible the anterior serratus is.

  • Great explanation you got here, nothing beats the mirror for me, but its always good to have many different methods of measuring results.

  • I use calipers, a scale, and measuring tape for shoulders, waist, and hips. Pretty basic, but that’s all you need! Oh yeah, pictures are probably the most important one, since that’s what you and others are really going to be noticing.

  • In the end you just have to look at how your clothes fit when you are trying to lose fat, especially in the beginning and compare yourself in photographs as you get leaner.
    You are right about calipers, I have had trainers take my measurements and I knew they were doing it wrong at times. Body fat testers I have found to be more consistent.
    Like you I would advise against weighing and measuring ourselves daily. Weekly or monthly is best.


  • Raymond,
    I agree that the mirror and photos are the best strategy. Sometimes it’s challenging to visually see results in the short term though which is why I turn to some of these other methods. I’m not worried about the actual number from these methods…as long as they’re headed in the right direction!

    Agreed. Be your own worst critic!

    Sounds like a nice balanced approach.

    The clothes fitting is a big one. Obsessing about results on a daily basis ends up hurting more than helping. Weekly is more than enough.


  • Dave,

    Congrats on your awesome results with XFLD. I haven’t gone through the program cycle to the letter yet, but I have taken bits and pieces and incorporated it into my existing routine. The biggest difference I’ve noticed is with muscle retention.

    Manipulating what I eat and when I eat (particularly around workouts) has helped me retain a lot of my strength gains better than I ever have before (difficult to balance this with an overall fat-loss oriented routine).

    As far as measurements, I use a body fat scale to track my weight, body fat %, and muscle mass % each week. Probably not the most accurate tool, but I’m fairly consistent with when I weigh myself and what type of state I’m in so it’s easier to identify trends.


  • Great Post Dave!

    I definitely think it’s important to track progress while dieting. Its very motivating to see improvements.

    I have to be honest I am not a fan of body fat scales and hand held body fat testers. Whenever I use them it says I’m like 16-18% body fat when I have very defined abs.

    My favorite measurement to track is the waist (around bellybutton). I know that if this measurement is going down than I am losing fat. Waist, chest, arms, shoulders and legs measurements are the key to tracking fat loss. In addition to weight ofcourse.

    I am probably going to get my body fat professionally tested (either bod pod or DXA scan) when I am a little bit leaner. My goal is to be about 6-7% body fat.


  • Dave,
    I remember using the fat callipers when I was in high school. It was a joke because nobody could use them properly.

    I think scale weight serves some purpose as does waist measurement, and strength maintenance. If your strength is going down, your body fat may be going up.

    Most importantly, as others have mentioned… we are great judges of how we look and feel when we really think about it. A quick look in the mirror often tells us so much more, even on a subconscious level! Kinda freaky..


  • I really like the DXA scan it’s the most accurate I have had, but if someone knows how to use the calipers properly you can at least tell what rate your dropping the fat.

    I think in the end the mirror is the best bet for me anyways.

  • Hi Dave, I’m definitely a big fan of taking before and after pics. Pictures don’t lie (usually…lol). When I measure body fat, I use 7 different sites and I learned the method from Precision Nutrition.

    Great article. Thanks for sharing your knowledge.

    Anna D.

  • Alykhan,
    It’s a good program; I’ll be writing about the full details soon. I think seeing trends in weight loss and fat loss is all you can really hope for.

    Fat testers can definitely be all over the place. Some are way too low; others are way too high…that’s why I just look for consistency. Waist measurement is great for tracking fat loss.

    You really have to be an expert with the body fat calipers.

    Fitness Guy,
    I haven’t had the scan done yet…none in my area. The mirror is a good way to go.

    As long as you’re true to yourself in before and after pics, they work great. The more sites, the better for measuring body fat.


  • Toni:

    I use a skin-fold caliper to measure mine like every so often. But photos don’t lie and neither does the mirror. I get into my swimsuit and stand in front of full-length mirror and assess myself honestly from different angles. It sounds a bit obsessive but it works for me. Also, there’s a website (Leigh that has photos of men and women with different percentages of body fat that I use to see if I resemble any of the women. It’s helpful to a certain extent to compare yourself to others in the same body fat range.

  • Toni,
    Sounds like a good method. I fall into the trap of obsessing over body fat percentage but what should really matter most is if I’m happy with the way I look. Too often I forget that…

  • Toni:

    I have heard that if you get down too low with your body fat that it could be detrimental to your health i.e.- the inability to stay warm, increased risk of dementia, etc. What is too low in terms of body fat for a woman? Obviously, I want to look good but not at the expense of my overall health. I have a long-term goal to reduce my body fat by another percent or two but hearing some of these things are making me rethink this future goal. Thanks in advance.

  • Toni,
    There is an essential level of body fat. I think it’s around 10-12% for women. However, that’s essential fat. I probably wouldn’t go below 15% as I think the general recommendations are not to go below 13-17%. I think you’ll know from your appearance and how you feel as to whether you’ve gone too far.

  • Toni:


    This is kind of a goofy question so I apologize in advance. When you lose some body fat particularly around your belly, is it normal for your navel to change in shape? For instance, if it was a deep ‘innie’ before and then it looks more ‘pushed out’ or flatter – if that makes any sense. I thought that only happened to people who got their body fat really, really low (like bodybuilders). Mine’s not all that low (I don’t think) at 17-18%. I just wasn’t expecting my midsection to change to *that* extent, lol.

  • Toni,
    I could see that happening. Think about being pregnant, then giving birth, and then losing weight. That’s the best analogy I can think of for a big change in stomach size which would tend to lead to the change in belly button. Not sure how common something like that is in general though.

  • Toni:

    I’ve discovered that I lost an inch off my waist (no easy feat given my build) so does that mean I’ve lost body fat if my bodyweight has remained the same? I’m really attempting to work on some of the areas that you pointed out so I have been tracking my progress.

  • Toni,
    Great to hear you’ve lost an inch off your waist…certainly not an easy task for anyone, especially someone who’s already in good shape. Unless you’ve managed to shift your fat from your stomach to some other place, I’d say it does mean you’ve lost fat and replaced it with muscle elsewhere (I’m guessing your arms/shoulders). Nice job!

  • Toni:

    I’ve been meaning to ask you: is there a site where you can refer me to that can help me figure out how much fat I’ve loss vs. muscle gained? Maybe one where you can plug in your measurements…

    I’m not great with numbers and I thought it was cool how you stated how much your wife lost and gained in the current post. I’m estimating right now but I’d love to have some definite numbers to go by. Thanks.

  • Toni,
    Here’s how I calculate fat loss and muscle gain. Take your weight and multiple by your body fat percentage. That’s the pounds of body fat you have. The difference between that and your weight is lean muscle. Now lean muscle includes everything from skeletal muscle to water to organs. If you want to isolate the skeletal muscle (which is what you can control by weight lifting), then you have to get a scale/body fat analyzer that provides that data.

    Here’s an example:
    Weight: 125lbs
    Percent body fat: 20%
    Pounds of fat: 25 (125 x 20%)
    Pounds of lean muscle: 100 (125 – 25)
    Percent skeletal muscle: 30%
    Pounds of skeletal muscle: 37.5 (125 x 30%)

    Track the changes week to week to see how much fat and muscle you’re losing or gaining.

    Question for you: how are you currently calculating body fat percentage? There are sites you can estimate body fat percentage based on measurements but I’m even less sold on their accuracy vs. calipers and scales (as bad as they can be sometimes).

    If you’d really like, I can email a spreadsheet template as well.


  • Toni:

    I’m currently using the caliper method. I’d love to get a scale that figures it out but I’ll wait until my digital scale goes before I buy one. I’ve gone on those sites that you mentioned and they have had me as high as 28% which I know is bogus because my abs are very visible. I know as a woman to have visible abs, you have to be around 18-19% at the very minimum.

    I’m confused as to how you came up with percent of skeletal muscle in the above example. I came up with this so far based on my current stats:

    Weight: 124lbs
    Percent body fat: 18%
    Pounds of fat: 22 (124 x 18%)
    Pounds of lean muscle: 102 (124-22)
    That’s as far as I got. What do you mean by track the weekly changes? Do you mean take my body fat weekly or something else?

    Sorry for all the questions. I think if you answer the additional questions I can probably figure it out but if I need you to email a template, I’ll let you know.


  • Toni:

    Also, I forgot to ask, is the scale that tells you your body fat and other data, really necessary to have to determine your progress?

  • Toni,
    Unfortunately calculations based on measurements can grossly overstate or potentially understate body fat percentage. The caliper is a reasonably accurate method though. As I said, the skeletal muscle is determined by a body fat analyzer. No easy way to calculate it. As for tracking changes, yes, I’m referring to calculating your body fat weekly and seeing how much weight/fat you’re losing week to week. With a caliper, it can be somewhat challenging because the week to week difference can be a fraction of a millimeter sometimes. That’s the only reason I like the body fat scale method. However, the fluctuations can be very frustrating. As I’ll describe when reviewing phase 2 of Visual Impact Muscle Building, the muscle change according to my scale doesn’t jive with my change in measurements and strength. Ultimately, no it’s not necessary, just another tool to help evaluate progress.

  • Toni:

    I guess every method has its potential flaws so it seems like the only sensible thing to do would be to keep using the same method for consistency. I’m still thinking about the body fat scale though..maybe down the road. It gives additional information which would be helpful, I think.

    Why is it that the skin at the bottom of my torso is almost paper-thin when I try to pinch it compared with the skin nearest my middle abs which is a little thicker? It seems like there are slight differences in skin thickness over my entire torso. Is that normal?

  • Toni,
    Unfortunately the best method is the most expensive one…getting professionally tested with DEXA or other advanced equipment. Not worth it in my opinion. I like to utilize multiple methods…mirror test, caliper, body fat scale, measurements, tracking how much I lift, etc. The body fat scale isn’t an integral part, just provides another estimate.

    I’m guessing that the thicker skin is due to storing slightly more fat in your middle abs…I don’t know for sure though.


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