More on the thermodynamics of weight loss

Okay.  I said I was through with Anthony Colpo, but now I’m going to quote from him once again.  What gives?

What gives is that I’m stuck in the airport in Seattle – my flight to Chicago is delayed for almost four hours because of bad weather in the Windy City.  I figured I would use this time to stick up a quick post about thermodynamics and provide a long quote from Robert McLeod, who writes Entropy Production, a physics (sort of) blog.  As you can see below, he pretty much trashes Bray and other nutritional researchers who blithely use the 1st Law of Thermodynamics to prove the old a-calorie-is-a-calorie notion.  To show the way the average nutritional writer looks at this law, I needed to find a quote.  As it works out, the only thing I have with me is Anthony’s book The Fat Loss Bible, which just happens to have the perfect quote.  So, sorry AC, I’m not really trying to pick on you.  And you certainly aren’t the only nutritional writer who thinks this way – you’re just the only one who has a quote handy I can use.

The First Law of Thermodynamics states that energy can neither be created nor destroyed. It can only be converted from one form to another. In other words, energy just doesn’t just magically disappear; it must be converted to something else. In the case of any excess calories you ingest, they will be stored as fat, used to accommodate an increase in lean tissue mass, or dissipated as heat through thermogenesis. Manipulating the proportion of protein, fat and carbohydrate you eat each day will not excuse you from the Law of Thermodynamics.

This is the way just about all nutritional scientists and writers look at the First Law.  Let’s take a look at how a physicist sees it.  Robert McLeod wrote a long post a while back reviewing Gary Taubes’ Good Calories, Bad Calories.  Near the end of the post, he discusses the energy balance equation and one of our old friends, Dr. George Bray, who gave Gary’s book a bad review in an obesity journal.  (I posted on this same review a couple of times here and here.)

Here’s what he says:

I was somewhat confused to see this [a nutritional description of the energy balance equation] Surely the nutritional scientists did not not really believe this, right? I mean, any idiot undergraduate students knows that the 1st Law is only useful in a closed system, and humans live on the planet Earth, not in an insulated box. Right?

Enter a rebuttal by G. Bray in the journal Obesity Reviews. Bray is a to be a major obesity researcher and one of the 2nd tier villains in the book. Taubes relates a story of Bray excising a section of a British report on obesity, where Bray removed the material pertaining to the relationship between insulin and obesity. He clearly has editorial support to make his case. Bray is one of the second-tier villains in Taubes’ book. Taubes has a footnote (p. 421), which suggests that Bray actively suppressed the carbohydrate-insulin hypothesis.

“According to Novin, when he wrote up his presentation for the conference proceedings Bray removed the last four pages, all of which were on the link between carbohydrates, insulin, hunger, and weight gain. “I couldn’t believe he would make that kind of arbitrary decision,” Novin said.”

Unfortunately, to a physicist this energy balance hypothesis looks like a silly hand-waving exercise, not a serious argument. Frankly I was flabbergasted when I first read this article. This conservation of energy argument is on the same scientific level as the ridiculous “drink cold water to lose weight” idiocy. A human organism is:

  1. Not in thermal equilibrium with their environment. Last time I checked I have a body temperature around 38 °C and spend most of my time in 21 °C rooms.
  2. Capable of significant mass flows (e.g. respiration).
  3. Capable of sequestering entropy (e.g. protein synthesis).

Is wearing a sweater fattening (by insulating you from your environment)? Here’s a quote from the rebuttal,

“Let me make my position very clear. Obesity is the result of a prolonged small positive energy surplus with fat storage as the result. An energy deficit produces weight loss and tips the balance in the opposite direction from overeating.”

According Bray’s thermodynamics argument, wearing sweaters makes you fat. This illustrates the greatest fallacy of trying to apply the 1st Law to a human: it makes the implication that living organisms consume kilocalories for the purpose of generating heat rather than perform useful work (i.e. breathing, contracting cardio and skeletal muscle, generating nervous action pulses, etc.). In reality heat is the waste product of basal metabolism. The first law does not distinguish between different types of energy. Heat, work are all equal under the First Law of Thermodynamics.

Applying the 1st Law to living organisms is Proof by Tautology. Yes, 1 + 1 = 2, but this tells us absolutely nothing about the underlying mechanics. The 1st Law does not (I repeat N-O-T) tell us whether you store excess energy in the form of fat, or bleed it off into the atmosphere by dilating blood vessels next to the skin, sweating, etc. To do so would require an accounting of entropy.

What would a semi-rigorous description of the thermodynamics of a human organism look like? Look at the title strip on the top of the page. See that equation in the background?

[The above is the background of the header of Robert McLeod’s blog]

This type of equation would be a bare starting point for energy balance in a complex system like a living organism. Good luck actually accounting for all the terms. Those Σs are sums.