Another Chink in the Simple Thermodynamics Model

I wonder how you’d go about reconciling the simple thermodynamics model of weight gain with this finding:

The trillions of bacteria that live in the gut — helping digest foods, making some vitamins, making amino acids — may help determine if a person is fat or thin.

The evidence is from a novel experiment involving mice and humans that is part of a growing fascination with gut bacteria and their role in health and diseases like irritable bowel syndrome and Crohn’s disease. In this case, the focus was on obesity. Researchers found pairs of human twins in which one was obese and the other lean. They transferred gut bacteria from these twins into mice and watched what happened. The mice with bacteria from fat twins grew fat; those that got bacteria from lean twins stayed lean.

The study, published online Thursday by the journal Science, is “pretty striking,” said Dr. Jeffrey S. Flier, an obesity researcher and the dean of the Harvard Medical School, who was not involved with the study. “It’s a very powerful set of experiments.”

What I’m referring to as the “simple thermodynamics model of weight gain” is the frequently assert belief that weight gain or loss can be determined based solely on calories consumed as food and calories expended as exercise. Despite the piles of evidence against it, the theory is remarkably persistent.

One of the things that strikes me about the experiment above is that it provides an alternative explanation for why we’ve been getting fatter as a society. It might not be due simply to eating too much and exercising too little even if that does play a role. The use of antibiotics, known to affect the intestinal flora, might play a role, too.

Maybe someday we won’t treat being fat as a character flaw and will start treating it as an actual, possibly communicable disease.

Hat tip: Glenn Reynolds

15 comments… add one
  • michael reynolds Link

    Ah, the little buggies in our tummies. It’s fascinating stuff.

    I can construct a thermodynamics answer to why I was suddenly able to lose weight (ate less, exercised more), a separate pharmaceutical (testosterone) model, and a bacteriological model which would involve two big rounds of Cipro (wiping out old flora) followed by adding a lot more fruits and veggies (adding new flora) and slashing alcohol (not killing so many flora with whiskey). And as is so often the case, I think the answer is (D) All of the above.

    The really creepy part of it is the possible connection between bacteria and perception, thought process, consciousness itself.

    I wonder how many people have spent any time thinking about what all of this means for our concepts of responsibility? The more we look like incredibly complex ecosystems affected by DNA, brain chemistry and now, parasites, the less old models of morality hold up.

  • In case I wasn’t being clear, my answer would be “all of the above”, too. But that completely demolishes the “character flaw” AKA “fat is a punishment for sin” theory that dominates right now.

  • PD Shaw Link

    I’m not sure its that revolutionary in terms of social mores. I think most people have long understood that there are genetic predispositions at work here, but individual behavior (easier for some than others) can make a difference. Can the obese twin become lean through extra effort?

    I agree with michael though that there is something creepy about beginning to see oneself as a host organism, in which not all of “us” is us.

  • Red Barchetta Link

    “I agree with michael though that there is something creepy about beginning to see oneself as a host organism, in which not all of “us” is us.”

    Deal with it, PD, its the way of life. Measure the “not us” in the billions. Gives you new respect for the human body.

    That the answer is so called “D,” all of the above is obvious, but it is a slight of hand. If you eat a tub of ice cream for desert after your carb rich and fatty protein supper every night you can exercise, take your Natures Holy Trinity etc all you want… will gain weight, and vice versa. There is no need to be overly literal. Every system, especially a human body, has many impacting variables. But some are primary, some are secondary and some are tertiary.

    Sadly, bacon, pancakes and ice cream are primary.

  • ... Link

    RB, I once lost weight on an ice cream diet. It started during some illness (probably one of my bouts with anti-biotic resistant strep throat) and persisted afterwards for a couple of weeks. I was probably eating nothing but ice cream for six weeks. Lost a bunch of weight. And yes, I ate a LOT of it.

  • Red Barchetta Link

    Write it up for the New England Journal of Medicine

  • michael reynolds Link

    I seem to recall cool sci-fi book series all about the world of nanotechnology that spends a lot of time looking at micro-flora. I wish I could recall the name. . . Oh, wait, here it is:

  • A little product placement, eh?

  • michael reynolds Link

    You’re in for 10% of all books sales generated via your comments section. Given the way BZRK is selling you won’t want to give up your day job.

  • PD Shaw Link

    “Grant gleefully exposes the biological ickiness of the body”

    So writing from personal experience?

    I read a short story by Michael Shea, The Autopsy (1980), a few weeks ago, about the horror of an alien sentient life nesting in a host body and taking control of a person’s mind. The mind retains awareness and the symbiot obtains pleasure or nourishment from the mental anguish. A bit too blood and guts for my taste, but the reader roots for the host to overcome his physical limitations.

  • ... Link

    Write it up for the New England Journal of Medicine

    Screw that, I’ll sell it to the evil Ice Cream Cabal. Not as well known (or as scary) as Big Oil or Big Pharma, but they’re more fun to work for. At least until the diabetes sets in.

  • Ben Wolf Link

    How much will you people pay for my bacteria? I have to eat 4,000 calories a day to keep my weight up.

    As for fat people: there’s a reason British cops are allowed to shoot them if they’re found eating chocolate.

  • Andy Link

    Time to put your barf on ebay Ben!

  • Ben Wolf Link

    I could do that, but I’m charging a premium for samples obtained alternatively.

  • jimbino Link

    As a physicist who has actually conducted calorimetry studies, I will say this:

    If you lack gut microbes to help you digest say, carbohydrates, you will eat as much as the next guy in “calories” while losing much more weight.

    Weight gain is determined by caloric intake times conversion efficiency, which might vary enormously among people, and not only those whose gut has been shortened or whose stomach has been stapled.

    That’s just simple science.

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