4 Facts about our Metabolism the Experts Don’t Tell Us

Read time: 2 minutes

Cut the Metabolic Crap!

Metabolism is a complex process misunderstood by those who perpetuate the myths that make weight loss more difficult for the rest of us. Here are 4 facts about our metabolism not well understood by these weight-loss experts.

1. Metabolism and Aging

We’ve heard it, maybe even said it. The moment we turn 30 (or some magic age) our metabolism takes a dive. The reality is that our metabolism doesn’t take a dive — it’s our physical activities that drop.

If human metabolism does slow as we age, it is by a very small margin, practically insignificant in the context of the real world. How insignificant?

Take for example: as compared to the metabolic rate in her twenties, a woman’s metabolism in her 50s burn only 4 calories fewer per hour. Though that’s interesting on paper, it’s a difference of only a stick of gum in the real world — which barely justifies the perpetual conversation about diminishing metabolism. All this woman has to do in the span of 30 years is take a couple bites fewer at dinner and go for a walk around the block.

[Besides, studies determining calorie expenditure in aging were based on normal-weight subjects that might have exhibited the natural loss of weight from diminishing DNA expression associated with getting old.]

2. Eating Less and Metabolism

In the weight-loss world, it is warned that weight loss by reducing calories could slow the metabolism.

Consider this: it’s been demonstrated that animals within the same species (including humans) having similar body sizes possess nearly identical basal metabolic rates — the basic metabolism required to merely stay alive. The larger the animal, the higher the metabolic rate, regardless of whether that size is mostly fat or lean tissues.

In other words, an obese man wearing an XXL shirt has nearly an identical basal metabolic rate of that in a lean man wearing the same-size shirt. (And, naturally, a third man wearing a medium-size shirt has a comparatively lower metabolism.)

A simple mathematical model can be used to predict basal metabolism — in other words, simple body weight (instead of body size) can approximate basal metabolism.

Metabolism is, therefore, an approximate reflection of body size. As we lose weight or size, our metabolism also decreases, regardless of muscle-to-fat ratio. This is a natural result of changing energy dynamics in weight loss, and is often misinterpreted as metabolic slow-down associated with calorie reduction.

When we weigh less, our metabolism is naturally lowered. That’s a good thing, not a bad thing. And a lower metabolic rate does not make us overweight — overeating and under-activity do.

3. Muscle Mass and Metabolism

A reduction in metabolism during weight loss is thought to be a result of muscle loss. But when we put into perspective the relative contribution of muscle mass to metabolism, we see that this is bunk.

Muscle mass contributes only 25% to the overall basal metabolic rate (Berne, 1998).

  • Kidneys – 200 cal per pound
  • Heart – 200 cal per pound
  • Brain – 109 cal per pound
  • Liver – 91 cal per pound
  • Muscle – 6 cal per pound
  • Fat – 2 cal per pound

The decrease in resting metabolism is associated with the natural reduction of overall tissue types, and not just of muscle.

4. Breakfast and Metabolism

Contrary to what we’ve been told, the metabolism doesn’t need a “kick-start” with breakfast. The metabolism responds to movement and energy demand. Just getting out of bed is a good kick-start.

Exercise, still the Best Metabolic Booster

The best “kick-start” to the metabolism, however, is (and will always be) exercise. But we can do that at any time of day.

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12 Responses to 4 Facts about our Metabolism the Experts Don’t Tell Us

  1. Bangkok Jay says:

    Voting this way up just for point #1 on metabolism and aging. What an enlightening fact debunking common beliefs.

    I was always under the impression that it was our metabolism during our university years that allowed us to eat like pigs. But could physical activity account for most of it or is there something else that kept many of us at more or less the same weight during those years? (apart from the “freshman year 15” pounds …guilty).

    PS Bring back the old LeanSaloon top banner photo!!! As a photographer it exhibited great lighting, contrast and form. It’s also a great draw into your site and I too was surprised to find it was your actual body vs some iStock photo. Ditch the robot; your real vascularity was better. Anyone else agree?

  2. KevinT says:

    Yep, this article knocks a lot of CW “facts” out the window. haha And I agree with Jay and the banner up top.

  3. Stephon says:

    Johnny,
    This is a great post,I just was asked by someone rather or not I had a high metabolism or not which is funny because of this post.Last post I asked how many metabolic conditioning workouts you recommended weekly and as you being pretty busy I understand that you can’t answer all questions.

    Since discovering this blog and doing 16-18 hour IFing daily,I am amazed by how much leaner I have become and my abs are bcoming more visible by the week it seems.I am even starting to see veins in the very lower region of my abs.Thank you so much for taking the complication out of getting lean and staying there.I do a lot of bodyweight conditioning and never knew I could look pretty good without a lot of equipment.Just keep up the good work please.

    • Johnny says:

      Hi Stephon,

      Thanks for the reminder to answer your question.

      My recommendation for the volume of metabolic conditioning workouts is this: do as few sessions as you can per week, for several weeks, and then see how your body responds. Add more if you feel you need to. Less if you wish. Either way, stay active as often as you can by moving around, no matter the intensity (like walking, standing, etc.).

      I do about one MetCon workout per week, on top of strength training. Sometimes two, sometimes zero. I plan to add some body weight exercise back in soon — when I’m less busy.

      Best,
      Johnny

  4. Sarah says:

    Thanks for all your previous help on the other thread. I’m making small steps right now to fast til noon. I really enjoy my coffee in the morning, however black coffee is just too bitter for me. I wondered if the creamer I put in it (40 cals exactly) and the Truvia sweetener is enough cals to break my fast. I am willing to look into other options. I am just finding it quite difficult to give up that coffee first thing! Thanks, I LOVE your website!

    • Johnny says:

      I’ve never gone a day without coffee with heavy cream. A few calories in the morning won’t deviate your body’s selection of fuel source t(stored fat) too much. Also, Truvia sweetener is virtually calorie-free and won’t distract the body’s fuel metabolism with glucose.

      Enjoy your coffee!

      Best,
      Johnny

  5. Nicole R says:

    Your blog kicks ass. I’ve been reading about health and fitness forever, but I’ve learned way more about health and fat loss on your blog over the last several months than over the last 15 years through other conventional sources. I never new fat loss and health could be so easy. Thanks and I sincerely hope you keep the good stuff coming!!!

  6. awesome write up. breakfast isn’t that important. listen to your body.

  7. Pingback: Carrying The Stone | The Lean Saloon

  8. Tracey says:

    Hi Johnny,
    I just stumbled onto your blog and love all the info. I am currently following a primal diet. I’ve actually kept off about 50lbs by watching portions etc, but eating this way has really helped me keep hunger in check. Am planning on incorporating IF shortly. Playing around right now with what is the right fit. My question is regarding zero calorie sweeteners. You mention above, “Truvia sweetener is virtually calorie-free and won’t distract the body’s fuel metabolism with glucose”….is this true for stevia etc?? Wondering if I’m better using honey even though it has calories..at least my body will recognize it as fuel and be more apt to be satiated. Know what I mean? Would love your experience? Thanks!

  9. David says:

    I just found your site and have been reading the back-dated blogs. I have been IF-ing on and off with very good sucess and now with your great content feel I can continue.
    2 questions:
    How about trigger foods? I can go without eating ice cream but once I eat it I want more. Do you try and advoid them, or try and IF after eating the triggerfoods?
    Elimination: When I eat I have no problem the next day with regular elimination. After IF I am not regular. Is that a cause of concern, or just part of eating less?

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