Can someone explain body composition?

  • My scale weight has gone down 22.5 pounds, they say I have only lost 1 pound of muscle, but my body fat has only gone down about 3 percent and is at about 40. that really confuses me. At this rate to get it down below 30 I would have to lose a lot more weight than we had agree I needed. I don't get it. Does anyone else understand this?
  • How are you measuring body fat? Fat pinchers? Or is this based on a scale?
  • on a scale
  • The scales are notoriously inaccurate, you really can only look at the trend, not the number itself. If you want a comparison try to get a more accurate method of body fat (calipers would probably be the easiest) and then compare that to what you're getting on the scale.
  • anything can tip the scale. even wet hair out of the shower.
  • I've been wanting to get back to you on this. I did some calculations for you.

    At 192.5 lbs, if your body fat % was 43%, then your fat free mass (muscle, bone, water, etc) was 110 lbs.

    If at 170 lbs your body fat % is 40%, then your fat free mass is 102 lbs.

    This means you've actually lost approximately 8 lbs of muscle and/or water weight (14.5 lbs fat).

    Not sure how they got the 1 lb loss calculation. The formula I used is a standard accepted calculation in the Exercise Physiology world.

    It is almost impossible not to lose muscle weight when losing as rapidly as we do on MRC (even with eating all that protein). My plan is once I get to my goal weight, hit the gym to rebuild muscle to get my body fat % down more while maintaining that weight. I did a calculation when I started this at my body fat % at that time (33%) and what weight I would be at if I got to 25%...which was 161 (it assumed no muscle loss). But I'm close to that weight and although I won't be back on campus to retest my body fat % until next week, I know I'm not at 25% and I know I've lost muscle. But I'll rebuild it.

    Also, a note about the way they test body fat. If it is a scale you step on, the machine actually only registers the fat in your lower body. So if you tend to carry more fat in the lower part of your body, then your percentage may read higher than your actual full body fat %. (Likewise, they make handheld machines that only calculate upper body). We do a lab in the class I teach comparing methods for body fat % testing, and they can be off by 5% or more from a more accurate method of using calipers (to do this properly, you need to find someone who is properly trained to do this).

    Let me know if you need more explanation or have more questions. Like I said I'd been wanting to do your calculations, but hadn't had a chance.
  • And a little more info...

    If you got to your goal weight of 160 and then maintained that weight while building muscle, you'd be at 30% if you got your lean body mass where it was before starting MRC (about 110ish pounds lean body mass). It can be done, but it will require strength training once you're done and maintaining the same weight (which means you'll still be losing fat weight).
  • Quote: I've been wanting to get back to you on this. I did some calculations for you.

    At 192.5 lbs, if your body fat % was 43%, then your fat free mass (muscle, bone, water, etc) was 110 lbs.

    If at 170 lbs your body fat % is 40%, then your fat free mass is 102 lbs.

    This means you've actually lost approximately 8 lbs of muscle and/or water weight (14.5 lbs fat).

    Not sure how they got the 1 lb loss calculation. The formula I used is a standard accepted calculation in the Exercise Physiology world.

    It is almost impossible not to lose muscle weight when losing as rapidly as we do on MRC (even with eating all that protein). My plan is once I get to my goal weight, hit the gym to rebuild muscle to get my body fat % down more while maintaining that weight. I did a calculation when I started this at my body fat % at that time (33%) and what weight I would be at if I got to 25%...which was 161 (it assumed no muscle loss). But I'm close to that weight and although I won't be back on campus to retest my body fat % until next week, I know I'm not at 25% and I know I've lost muscle. But I'll rebuild it.

    Also, a note about the way they test body fat. If it is a scale you step on, the machine actually only registers the fat in your lower body. So if you tend to carry more fat in the lower part of your body, then your percentage may read higher than your actual full body fat %. (Likewise, they make handheld machines that only calculate upper body). We do a lab in the class I teach comparing methods for body fat % testing, and they can be off by 5% or more from a more accurate method of using calipers (to do this properly, you need to find someone who is properly trained to do this).

    Let me know if you need more explanation or have more questions. Like I said I'd been wanting to do your calculations, but hadn't had a chance.
    I always ask for a copy of my ,body compostion analyzer, that MRC does every month or so. That helps to understand things a little better also.
  • Gina, thank you SO much! I just knew something was up. This is my ongoing gripe with MRC- they don't know enough about the science. I do light weight training now but am inconsistent. Having the real info really motivates me and I think you have the right idea of changing the focus to building strength once I am at 160. Building muscle would not show further loss on the scale, but fat percentage would continue to go down, right?

    Next time they do the composition I will make a point to bring home a copy and post again on this. I think it is important. May I ask: what is your profession ?
  • I'm an athletic trainer and I teach exercise physiology at a university...also in process of becoming a wellness consultant or coach.
  • That is excellent! You are going to be a good one. Thanks again.