Metabolic rate is determined by Fat Free Mass

The Claim: Your metabolic rate is determined by your fat free mass

Answer: FACT

Your metabolic rate is most closely correlated with your fat free mass (lean body mass). Your fat free mass is all the parts of your body that aren’t fat (rather obvious explanation)…this includes organs, bones, skeletal muscles and extracellular water.

The most metabolically active tissue of your lean body mass is your internal organs which account for approx 80% of your BMR.

The metabolic activity of your organs is tightly regulated and predictable and there isn’t much you can do to change it. Don’t bother comparing yourself to others (as someone else’s ability to burn calories will never help you burn them)

There are some pretty good metabolic rate calculators online that do a decent job of estimating metabolic rate.

I’m 6’0 tall and about 183lbs and my BMR comes out to around 1900 calories per day which is pretty accurate.

If you use a metabolic rate calculator online don’t bother with the activity factor calculation because they tend to waaay overestimate calories burned from activity. If anything just use the BMR calculated as a general guideline if what you need…oh, and probably go with the lowest estimate you can find as some of the calculators also overestimate quite a bit.

John

Posted by johnbarban in metabolism
Tags: metabolic rate |11 Comments

11 Responses to “Metabolic rate is determined by Fat Free Mass”

  1. Brandon Says:
    February 18th, 2010 at 10:32 am

    Its odd that the idea of a pound of muscle burns 50 calories a day at rest caught on the way it did..Just another myth to unlearn :D Keep up the good work, Love the site and the new phi-life podcasts

  2. Michael H Says:
    February 18th, 2010 at 1:20 pm

    So far I have correct answers! I wrote FT on first two and F on this one! SWEET!

  3. MikeGP Says:
    February 18th, 2010 at 4:28 pm

    I actually chose Factoid for this one, because a pound of fat burns 2 cals a day. Its very little and doesnt make much difference, but DOES count towards the BMR.

  4. johnbarban Says:
    February 18th, 2010 at 9:01 pm

    Mike,

    The only consistent predictor of metabolic rate is the total fat free mass. Of that the internal organs make up most of the calories burned. Skeletal muscle accounts for about 15% of BMR. So this is a fact, but most people assume lean body mass (fat free mass) is all muscles and don’t understand that organs play a much bigger role for calorie burning than muscles.

    JB

  5. biggahboy Says:
    February 19th, 2010 at 12:41 am

    Ok I want to understand and use this “metabolism” term well. I looked up the meaning of “METABOLISM: Definition Metabolism refers to all the physical and chemical processes in the body that create and use energy, such as Digesting food and nutrients, Controlling body temperature e.t.c

    1. so does the “processes” refer to burning of calories or fat loss?
    2. can these “processes” be increased, people always say “you can increase your metabolism” “you have a slow metabolism”
    3. do some people have faster/slower metabolisms?

  6. Wazzup Says:
    February 19th, 2010 at 4:01 am

    Too be complete:

    Organ or tissue Organ metabolic rate % Overall Weight (% ABW)
    (kcal/kg/day) REE (kg)
    Adipose 4.5 4 15.0 (21.4)
    Other 12 16 23.2 (33.1)
    Muscle 13 22 28.0 (40.0)
    Liver 200 21 1.8 (2.6)
    Brain 240 22 1.4 (2.0)
    Heart 400 9 0.3 (0.5)
    Kidneys 400 8 0.3 (0.5)

  7. johnbarban Says:
    February 19th, 2010 at 11:31 am

    Biggahboy,

    All these processes require energy, so everything that is encompassed under the word metabolism is referring to energy consuming events. It’s not quite correct to speak of metabolism in terms of ‘speed’.

    Probably better to think of it in terms of ‘work’…as in, how much work is your body doing…even that is a weak analogy. In reality it’s nothing that you need to be concerned with anyway.

    JB

  8. MikeGP Says:
    February 19th, 2010 at 4:26 pm

    Then why is it that some times you have tons of energy vs low energy days….Often people that switch to a more “healthy” style of eating, claim to have an increase in energy, what does the energy you feel during the day (high vs low) have to do with metabolism?

  9. MikeGP Says:
    February 19th, 2010 at 4:26 pm

    Or does it have to do more with glucose in the body? spikes of insulin, etc…

  10. Jordan Says:
    February 19th, 2010 at 4:57 pm

    I’m not sure what these numbers mean. Can someone explain them for me?

  11. johnbarban Says:
    February 20th, 2010 at 12:32 pm

    It’s probably a combination of less total calories and an attitude/expectation.

    The more food you eat the more it will tend to cause you to want to rest and eventually sleep.

    JB

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