Friday, March 9, 2012

Biology Lesson

In one of my classes today, my professor did a quick aside review on the Malthusian theory of population, which was an 18th century postulation that the human population would grow exponentially until it outstripped the planet's resources and agricultural production - way too many people squeezing into limited space, fighting each other off for limited food, hacking each other up and going cannibal etc. I made that last one up. It could probably happen, though.

BUT not to worry, it has since been pretty much determined that Malthus' gloomy prediction won't come true. Why? Because the population rate will not increase exponentially for ever and ever. After the initial period of exponential increase, mediating factors kick in to slow the growth rate. The earth likes balance. Humans take from the earth, but we also give back, and biology wants to maintain this homeostasis. So eventually, the population levels off. There might be periods of flux one way or the other, but the population won't spiral up out of control. From my understand, this general pattern doesn't just apply to the human population, but also to things like animals, bacteria, fungi, etc. (This is a reeeeally rough explanation. I'm not a scientist. My facts are coming from five minutes of a class lecture, my vague memory of high school biology, and some poking around on Wikipedia. Scientifically-inclined people, definitely chime in and correct me if I've got it totally wrong.)

Anyway, does this remind anyone else of set point theory? Maybe it's just because weight gain is on my mind all the time lately, but instead of seeing my professor standing up there with his little laser pointer, I was seeing my dietician J in her office trying to convince me that a 0.8 lb blip on the scale does not signify impending obesity. (I'll gladly accept second opinions on that one though!) On an appropriate meal plan, the body of an underweight anorexic will gain weight until enough weight has been gained, and then it will stop. I haven't done enough research on the set point idea to know exactly where I stand on that one (if I'm not mistaken, it's still somewhat controversial, no?), but I definitely believe that the body has a healthy range within which it wants to stay, and within which it will stay if fed a healthy, reasonable number of calories.

Bodies, populations - nothing can grow exponentially forever. It just can't. I know this. But for some reason, it's much easier for me to believe that microbial bacteria in the ocean will obey the laws of biology and physics than for me to believe that my body will behave in an equally appropriate fashion. Logic: reveal yourself!


  1. I actually believe pretty heartily in the set point theory, if only based on my personal experience. If I'm eating properly, exercising in moderation, and not engaging in ED symptoms, my body will naturally hang around a certain weight (plus or minus a few pounds, accounting for normal flux, etc). My problem isn't in believing in the theory, it's in knowing (roughly) what my set point is and HATING that number and size. I am, from what I can tell, not one of those recovering anorexics that will naturally settle at an adorably petite size, but, due to genetics and whatever else, will settle higher than I'm comfortable with.

    I mean "comfortable with" is all a load of crock anyway when you're recovering from an ED, but whatever. I'm not comfortable now, I wasn't comfortable X pounds up, and I wasn't comfortable X pounds down. I suppose I should at least be grateful that my body is functioning more normally now? :-/

    Officially chalking this up to the LEAST helpful comment ever. Sorry. :-p

  2. I believe in set points (also from personal experience), but I also believe that set points can shift. For instance, when I was recovering, my Set point was X (which represents about a 3 pound range). As I held my intake steady (and even increased it) and kept exercise steady, about 15 months after weight restoration to X and 15 months of super consistently following a meal plan, my body mysteriously went to X - Y. And, now, my body stays in the X - Y range and it is hard for my body to move out of that new range. I really do believe my set point shifted. I don't have articles to name off the top of my head, but I've heard that set points can shift. I've heard that yo-yo dietiting can raise your set point. I've heard that people who are obese may have manipulated their set point to a higher one, but, over time, their set point can decrease. I may possibly be making all of this up, but I don't think so....

  3. You win loads more points upon the awesome I had already granted for finding a way to tie Malthusian theory into your blog. Rock on, my friend, biology is awesome...a great example of this is deer in the U.S. We've wiped out their natural predators, so in areas where they weren't hunted enough, their populations rocketed until they exhausted their food supply and had mass die-offs. Nature likes balance.

    I definitely have a very hard time trusting that the set point phenomenon would apply to me as well. To be honest, though, every experience/observation I can think of really does support that it does indeed exist. My mom lost a lot of weight (three kids' worth of "baby weight") my first couple of years of college, and when she went back to school herself a few years ago and essentially gave up her entire exercise regimen (she had been up to running half-marathons), she put a bit of weight back on....but honestly not that much. It was like her body had resettled at its old, pre-baby set point. That's one anecdote, but it happens all the time.

    Honestly, bodies are smart, and they do "want" to be healthy. I think it's really common for us to treat them like a kid that we assume is going to be a rebellious teenager, micromanaging until the relationship becomes toxic, instead of giving them the chance to prove that they are way smarter and more responsible that we've been giving them credit for.

    1. Cammy! Whew, I was hoping you'd step in and take the science off my hands. Hopefully I didn't completely butcher it. Blame Wikipedia.