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