Human Metabolism Variation, or, Useful Trolls

So there’s an MFS troll over at BFB forums, and it’s actually been kind of useful. I had a dusty old primer on the human metabolism that I lost track of, and when it brought up the common fallacious argument that all humans have around the same basal metabolic rate and that fat is naturally attributed to overeating/underexercising, I took the opportunity to do a little digging. I’ve known for a while that mitochondrial efficiency is a large part of metabolic variation between individuals — you know, one of those things you research once for a few days, read through a fuckload of articles and get a good idea of, and then don’t save the research path.

So I did some fresh research. And that’s why this post is also titled, “Useful Trolls.” Because, while they’re mostly just dumb and annoying, sometimes the pseudosmart ones can actually force you to compile your research. So thanks for the holiday gift, lovely MFS troll. Hugs!

NOTE: I will add these links to the “Truth Behind Fat” page.

First thing’s first, here’s a better ‘equation’ of human metabolism (that is, to replace ‘2000 cal = food – exercise = weight maintenance’). I’ve linked the terms. The ‘equation’ is from this article [1].

Classically, three major biochemical systems are believed to contribute to basal thermogenesis: futile cycles, Na+/K+ATPase activity, and mitochondrial proton leak [2 – 3].

One of the most interesting parts of the ‘equation’ above, to me, is the mitochondrial proton leak, which is highly (if not entirely) genetic. That would be the second item in this quote (link):

Discrete gene sets may prevent or facilitate obesity in humans by influencing food intake (e.g., leptin), by altering the ability of skeletal muscle to dispose of excess energy (e.g., uncoupling proteins [UCPs]), or by influencing the capacity of the adipocyte to accumulate triglyceride (e.g., CD-36, perilipin). [4]

There’s a lot more research one can do, here. But I thought that during this season of panic concerning overeating, taking a closer look at the human metabolism and its inextricable connections to genetics would be a nice little present for y’all.

Happy Holidays!

SOME REFERENCES

1. W. Timothy Garvey. “The role of uncoupling protein 3 in human physiology.” J. Clin. Invest. 111(4): 438-441 (2003). doi:10.1172/JCI17835. link

2. (rat study) Various. “Characterization of weight loss and weight regain mechanisms after Roux-en-Y gastric bypass in rats.” Am J Physiol Regul Integr Comp Physiol 293: R1474-R1489, 2007. link

3. (rat study) http://grande.nal.usda.gov/ibids/index.php?mode2=detail&origin=ibids_references&therow=108372

4. Various. “Decreased Mitochondrial Proton Leak and Reduced Expression of Uncoupling Protein 3 in Skeletal Muscle of Obese Diet-Resistant Women.” doi: 10.2337/diabetes.51.8.2459 Diabetes August 2002 vol. 51 no. 8 2459-2466 link

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10 comments on “Human Metabolism Variation, or, Useful Trolls

  1. elizebethturnquist says:

    I love that you did this. It’s something “I” would do. I love the passion and that a troll inspired you. Very cool.

    But, I have to a admit, I completely don’t understand the equation you present. And I really WANT to understand it. I want to be able to relay it to others.

    I was wondering if you could explain it further?

    Also, I’m Pro-Elevator-Pitch. I don’t know how you feel about taking concepts like these accessible to the layperson. I understand if your against it.

    But, if your interested, I’d love to dialog through comments about distilling this concept.

    • bigliberty says:

      Hi Elizebeth,

      I would love to go into it more, in layman’s terms. It gives me a change to really brush up on my bio/chem. I’ll plan my next post around it.

      Cheers!

  2. This is really interesting. I would love to have an alternative to the Harris-Benedict or the WHO equations for individual energy requirements, just for interest’s sake.

    I’ve been looking into another equation that could possibly be used to determine an individual’s set-point weight (provided you had indirect calorimetry equipment available.) When the holiday madness is over, I’ll email you some more details and maybe you can help me with it.

  3. bigliberty says:

    I wouldn’t mind helping you with it, but I don’t know how much help I could be! lol My main fields are physics/math/complexity science, which means I can read scientific articles in other disciplines and know reasonably what’s going on (my decent undergrad bio/chem classes also help), but I’m definitely no expert 😉

    However, I’m all for as much scientific collaboration within FA as possible. I think it’s nice to have a good contingent of people who can speak on the science of fat with reasonable understanding and expertise (beyond common sense level). Because fatness *is* highly genetic, and the misunderstanding of the human metabolism leads to a lot of incorrect assumptions that get bundled into some impregnable anti-fat physics argument.

    Thermodynamics is, of course, correct: if you store more than you use or that is lost through malabsorption of some kind, that becomes fat. But human beings are programmed differently from one another, and one person might store more than another person, or generate less heat doing the same work. And the mitochondrial proton leak has been postulated to account for quite a large part of the difference between ‘what is burned’ between individuals.

    Most of the studies done which actually expose the truth behind fat do so, not with the intent of purely explaining human fatness, but with the intent of producing drugs that will make fat people permanently thin. So there are a lot of rat studies to wade through, and other studies which are filled with the standard obesity epidemic hype in the abstract, but ultimately they are increasingly showing the undeniable link between genetics and fatness, and that no, Virginia, us fatties aren’t “broken” people who would be thin if only we were more morally endowed.

  4. Not to gush, or anything, but you both rock. Oh, and I laughed when I read “morally endowed.”

    “as much scientific collaboration within FA as possible”

    You don’t know how much it warms my heart to hear you say this. I’m not an academic. BUT I’m into skepticism and scientific articles don’t scare me. And the geek in me is fascinated by the science of fat.

    I’ve been struggling with the whole “set point” theory. I think it the public perceives that to mean that we are genetically predisposed to a single weight. When what I really think it means is that our bodies tend to fight change.

    I’ve been looking for an idea that could go hand in hand with “set point” theory. And, based on what I’ve read, I’ve been leaning towards the idea that we gain or loose weight at different rates, based on our genetic makeup. Which admits that, yes, we can loose or gain weight BUT depending on our genetic programing our body handles that process differently.

    So…you’ve just lead me down the path I’ve been desperately searching for! Oh, and please feel free to correct me if you feel I’ve stumbled in my interpretation of the science.

    (Homework for tonight, read up on “mitochondrial proton leak,” “Harris-Benedict,” and the “WHO equation.”)

  5. bigliberty says:

    Elizebeth,

    From what I have gathered in my personal research on the subject, it’s not that we’re born with a switch as it were, set to X adult lbs. It’s more like height (and in some ways not, will get to that later on), in that we’re predisposed to be in a certain range and our health as children and young adults will place us on the higher, middle, or lower part of that range. (A state of famine stunts growth, a state of plenty encourages it)

    The predisposition to be in a certain range is the genetic component of weight, which some have estimated to be at about 77% (that is, adult weight is 77% determined by genetics). That’s pretty close to how much height is determined by genetics.

    Bodies tending to fight change is another story, though I think that something else that we’re predisposed to do largely by genetics. It isn’t out of the range of possibility that metabolic activity can be influenced by environment: those who have restrictive eating disorders, for instance, can alter their metabolisms when taken to the extreme. Dieters encounter “plateaus,” and for certain people trying to gain weight is as difficult to other people as losing it, and then there’s the lightning-quick ease of regaining weight after a restrictive diet.

    There’s already proof that metabolisms can be altered by mechanisms programmed in us: pregnant women typically gain more weight than just “baby” in order to have stores to breast-feed. Those who are recovering from major wounds/surgery tend to have to take in more energy. As we age through our thirties and into our sixties, gaining weight is easier, then in our late sixties and beyond, losing weight is more typical.

    The likely explanation behind the current, snapshot fatness of each and every one of is a combination of genetic predisposition towards a certain weight range, heath during childhood, a genetic predisposition which makes it easier to gain/lose, our age, and whether we live in forced/chosen famine or abundance. Long-term level of fatness corrects for various states of famine/abundance.

  6. Lindsay says:

    Thanks for this, BL.

    (I have a degree in biochemistry, so all those variables you mention influencing metabolic rate make total sense to me; I just hadn’t really researched it myself.)

    I’ve also noticed the useful-troll phenomenon. Blogging (in my case, mostly about autism science — what little there is, haha — the discourse around which is similarly plagued with misinformation and ignorance) has made me so much more diligent about researching things.

  7. BigLiberty –

    I was aware of most of the points you speak of but I loved the way you summed it all up. I think that’s a great jumping off point for an elevator pitch.

    I’m still working on the wording. But here goes.

    —-

    Weight is a part of a complex system. It’s like thermodynamics with a bunch of buts* attached. Each “but” coming from a genetic predisposition.

    Thermodynamics, but…

    -we tend to a certain weight range.
    -we burn energy (ie loose weight) at different rates.
    -we conserve energy (ie gain weight) at different rates.
    -our weight is affected by our age. After 30 we tend gain and after 60 we tend to loose.
    -pregnancy, disease, and other body changes can spark our bodies into a states of gain or loss.

    —-

    If you have suggestions for edits I’d love to hear them. (*exceptions to the rule could be another phrasing, in place of “but.”)

    I also was pleasantly surprised to hear about the genetics predisposition of height being similar to the genetics of weight. I did not know that.

    Oh, and I had not thought to put the part about age that way. I knew that after 30 we tend to gain and, at a certain point, we tend towards loosing. But you summed it up in a very understandable way.

    All around, bravo.

    I haven’t had a chance to dive into my homework. I spent all day cooking, ate one plate of the yummy xmas food I’d been cooking, and then me and my husband promptly fell into a food induced coma.

    Talk more soon.
    Elizebeth

  8. atchka says:

    I have a WordPress account now, so I can finally comment. HOORAY for me!

    This is fascinating, but a little opaque for me. How does that mitochondrial proton leak actually cause the difference in metabolism? I know I’m going to have to do my homework like Elizabeth, but I thought I’d see if one of you geniuses could explain it.

    I recently starting digging into the science, mainly through Michelle’s (the Fat Nutritionist’s) list of articles (just the free ones I could find) she has down the side bar on her page. I’m surprised at how much I (think I) understand.

    But one article that kind of blew my mind and seems to fit in with this is the one titled “Is the Energy Homeostasis System Inherently Biased Toward Weight Gain?” (although the deeper into the article I got, the more science-y it got, and the less I absorbed).

    But I found the explanation fascinating that evolutionarily speaking, the body has these processes that kick in to prevent you from losing weight in the long term. My wife explained (and I vaguely remember this from high school biology) that fat cells are never lost. Only shrunk. Which made me wonder whether the fact that those cells are always there, if they wouldn’t just be “hungry,” so to speak, and force your body to maintain its weight to keep them nourished.

    I just got “Rethinking Thin,” “HAES,” and “Fat Politics” for Christmas and I’m really looking forward to them. But until my understanding is updating, here’s how I currently understand weight:

    You inherit your body from your parents, so let’s say I got my Dad’s body. As I grow older, my body will store fat until I reach that genetic marker. If I have a poor diet and lead a sedentary lifestyle, then I can blow past that set point and gain more weight. But if I eat healthy and lead an active lifestyle, I could drop back down to that set point, but probably no less.

    Is that about right? And if I gain past my set point, how does that relate to the “your body won’t let you lose weight” part?

    I’m so desperately trying to find out the closest thing to the truth, but it’s so hard with the thousands of mixed messages. Ugh.

    Anyway, I just read your “Truth Behind Fat” page and I’m going to link to it on my “Get the FATs —” page. Hope you don’t mind. You’ve got a ready-made 101 page right there for the taking. 🙂

    Peace,
    Shannon

  9. vesta44 says:

    BL – This is a little off-topic, but our troll has been banned from BFB, just thought I’d give you a head’s up if you hadn’t checked back lately.

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