Of Thermodynamics, Complexity, Closed Systems & Equilibrium

In light of this recent post, I've been thinking more and more again on this topic.  And when Adam Kossloff liberally quoted from Entropy Production's author Robert McCleod's rebuttal to rebuttal or whatever in the Taubes/Bray dust-up, I just had to weigh in on this.

Let me preface this by saying that I have a bit of a unique perspective on this issue having learned and applied thermodynamics in the context of several disciplines,  from both a scientific and engineering perspective.  I've worked in a number of fields and interacted with many who have only been exposed to these concepts in one context or the other.  Now what I'm about to say is obviously a generalization,  so keep in mind I'm not saying "all", just in general.  But one thing I've noticed is that engineers and physicists tend to not really "get" chemistry, or worse, biology, because they are used to things being cut and dry.  I've heard some certifiable geniuses in engineering disciplines make some extremely ... well ... stupid comments about something biological.  For the physicist, drop a ball off a cliff and pretty much we can figure the time it will take to reach the bottom, its velocity at impact and all that.  But one can mix A & B in a test tube, and almost inevitably the resulting amount of C that might be produced differs from predictions.  It is almost a given that one will be asked to provide possible explanations for the differences between predicted and observed values when writing up a lab report.  Throw in something living, like bacteria in a petri dish, and it only gets worse.  So the physicists and engineers tend to resort to the "it's all too complicated to explain" refrain because there are just so many other factors at play that we can't possibly seek to understand or explain.

The same happens to biologists and chemists looking the other direction.  Truth is, in most undergraduate programs, the bio majors (or softer life science related fields) and many chem majors take a different physics class, one that is not calculus based, and may not even be required to take a course in differential equations or even calculus.  The equation at the top of McLeod's blog looks daunting, as do many of the discussions of Hall & Chow.  So one can feasibly be a bio/chem/biochem whiz and still that thermo equation might as well be written in Chinese.  So that equation looks foreign so geez ... how can we ever seek to understand something so complicated?   It's a form of intellectual bullying IMO.  Make something so complicated that it can't possibly be understood and you can baffle with bullshit all day long.

Indeed McLeod's opening salvo on this topic is:  "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? 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."

I hold that just because most of us couldn't handle the math of a comprehensive analysis does not preclude understanding the basics, nor does it preclude applying that approximation to real life systems.  The simple concept of mass balance HAS to hold.   The one thing I think we can all agree on is that the C, H, O, N and assorted other atoms in the chemicals we ingest (and everything is ultimately a chemical) cannot be magically converted to other atoms or disappear into thin air.  So if you eat it, it must either come out (exhaled or excreted) or it is going to show up on the bathroom scale.  We can argue until the grassfed cows come home whether it gets accumulated in our fat cells or where it goes, but if it hasn't come out, it's there and it will increase your mass.   I talked about this a bit here.  I'm always amazed by the number of reasonably intelligent folks who will argue against the fact that I can't gain more than a pound of fat eating a pound of cookies.

Perhaps it's because the major ways chemicals make it "out" of our bodies are invisible:  we exhale CO2, and urinate out dissolved urea (NH2)2CO (to a lesser degree we exhale and urinate ketones under some circumstances).  But it does have to go out or it will add to that reading on the bathroom scale.

So, this notion that we might need to understand the nitty gritty of every biochemical reaction occurring and all hormones, enzymes, incretins, lectins, this-kine, that-kine, lactones, altones (OK I'm making shit up now)  etc. to understand a basic requirement that, in the end, energy in = energy out (all cause) + energy stored is an attempt at distraction.  Our day-to-day inefficiencies and the minutia of metabolic paths, etc. do not need to be understood in order to work with this simplified understanding.  Anyone who says otherwise is trying to tell you that you can't understand that you have to put 10 gallons of gas into the tank of a car that gets 25 mpg to go 250 miles because we can't quantify entropy losses in the pistons and whatnot.  Nonsense!  On a day-to-day basis our engines and such do not change much in efficiency.  So too, our basal metabolisms vary by only a couple of percent a day, this means we can  largely ignore these minute changes.

Does this mean that if I overeat 3500 cals I'll gain exactly 1 lb of fat?  Or vice versa?  Of course not.  For one thing, we never gain 100% fat (or lose it for that matter), but also, this is where those other factors like TEF, ketone spillage, transient inefficiencies using dormant metabolic pathways or further swamping pathways over-swamped to begin with and such come into play.  Still, study after study demonstrates that we can do little with diet to manipulate these to any large degree, and when we can, it involves long term changes to an extreme.

Bottom line, acknowledging energy balance does not require being able to explain it fully or calculate it exactly.

OK, I probably went off on a bit of a tangent there, but this is how I start to think when I read things like:

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?

[Important edit:  When I first wrote this I used McLeod equating closed system with an isolated system.  It doesn't really change the argument so I'll leave it as it is but point out that technically there are three kinds of systems:  open, closed and isolated.  Open systems exchange energy and matter with the environment, closed systems do not exchange matter, but do exchange energy, while in isolated systems (e.g. in an insulated box) there is no exchange of matter or energy between the system and its surroundings.  The crux of my argument is that it applies to open systems, so with this caveat I'll let the technical error stand.]

 
Um, no.  Firstly, closed systems have been studied, or has McLeod not heard of the metabolic chamber and is he not aware of how food calorie factors were derived in the first place?  That aside, what "idiot undergraduate student" hasn't done energy balance equations in open systems by either (a) defining a closed system  (e.g. in chemistry we can perform a reaction in a closed, insulated container) or (b) adding energy in and energy out terms and treating something (e.g. an engine) as "black box" of sorts. (EDIT:  ironic that Kosloff likes to talk about black boxes, this is exactly what "practicing" CICO would be).  Surely McLeod has done either of these two before?  I'll give an example.  Feel free to skip this :D

Physical Example:  At some initial point di a box of mass m is sliding across a smooth horizontal surface.  Take di to be zero displacement, the box has an initial velocity, vi.  The box comes to rest at df.  Find the force of kinetic friction between the box and the surface.   Here, we could come up with all sorts of energy terms to describe the box, but the only ones that matter (because the others don't change) are the horizontal kinetic energy terms.

1. Our equation:  Ef = Ei - Wkfriction .  
2. The only E of note is kinetic energy:  KE =  ½mv²
3. Since the box comes to a stop, vf = 0 thus Ef = 0
4. Rearranging:  Ei = Wkfriction .  
5. Now Wkfriction   = Ffriction·d
6. Now we have have ½mvi² = Ffriction·df ... 
7. Rearrange to solve for Ffriction.  

Or was I the only idiot undergrad who ever went through such calculations?  The box is neither a closed system, e.g. we have non-conservative (dissipatory)  forces at play, nor at any sort of equilibrium with the environment.  We can look at this as a closed system by expanding it to include the box + evironment, or, more commonly, we can treat the box as a "black box" and accounting for energy in/out.  If I were also pushing the box, then we would have to add a mechanical work "in", Wk=F·d, term.  If we even care, yes, friction converts kinetic energy to thermal energy (which is why things heat up when we rub them together), and yes, we have to ignore other terms such as air resistance, etc.  If we were able to, we could employ some higher mathematics and computers to do the calculations for air resistance though, it would be a matter of whether the contribution is of significant magnitude vs. the friction component to make the effort worthwhile.  But in the end this doesn't violate TFLOT.   We treat this as an irreversible process, equilibrium doesn't even enter into this discussion.

So McCleod goes on:

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.

Perhaps this is where Eades co-opted his arguments from, but this is nonsense.  We actually can lose weight drinking cold water, sitting in cold rooms, taking cold showers and the like because thermal energy lost to the environment is easily accounted for in TFLOT.  The fact that the caloric expenditures of such strategies are often minute and likely unmeasurable (kinda like Eades' insensible water weight losses during sleep nonsense) does not negate energy balance.  Drink enough icy water and shiver me timbers long enough w/o dying of hypothermia and I'll lose a bit of fat mass!  What is idiocy folks is to imply that:

According Bray's thermodynamics argument, wearing sweaters makes you fat.

No, because the human organism does not even try to harness thermal energy to convert it to another form.  This is the problem with those who have mostly been introduced to what we most commonly associate with "thermo"  in the context of the Carnot Cycle/Steam Engine.  In this context entropy does come into play because the steam/combustion engines DO (unlike living organisms) attempt to convert thermal energy to mechanical work.  Heat liberated from combusted fuel causes a gas to want to expand.  If that gas is contained in a piston/cylinder configuration, the expanding gas will move the piston (do mechanical work), but the work never equals energy liberated by the combusted fuel.  This has ZERO relevance to humans.  But, wearing a sweater or hanging out in temperature controlled environments will decrease how much energy your body must expend to maintain body temperature.

Backing up a bit in McLeod's supposedly brilliant dissection of energy balance:

A human organism is: 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.

So?  Does anyone argue that it is?  Does anyone actually dispute that we must expend energy to maintain a relatively constant body temperature?  This is a ridiculous argument.

A human organism is: Capable of significant mass flows (e.g. respiration).

So?  Isn't that the point?  How does this negate TFLOT??  Expired CO2 is used to measure energy expenditure.  An operating engine involves significant mass flows (gasoline in, combustion products out).  But flow out in humans occurs through glycolysis, beta-oxidation of lipids, Krebs and the ETC.  That's when stuff gets reduced to a form that can flow out (CO2).  

A human organism is: Capable of sequestering entropy (e.g. protein synthesis).

I think referring to synthesis reactions as "sequestering entropy" is absurd.  We actually CAN quantify the energy required to synthesize molecules.  Indeed our bodies are really electrochemical engines that harness the chemical energy released by one reaction in an orchestrated manner to drive chemical reactions against their spontaneous direction all the time.   This is no different than harnessing thermal energy to drive a mechanical system, only conversion of chemical energy from one form to the other is lossless compared to the losses in a steam engine converting thermal energy to mechanical work.   McLeod goes on:

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.

Yes, all forms of energy are equal in TFLOT, but so long as we're not looking at the conversion of thermal energy to other forms such as mechanical work, TFLOT serves us rather well.  Who has implied that we consume energy for heat generation rather than useful work?  The term "futile cycle" argues against this as most energy produced is used to do other "work".  Although called "futile", such cycles (under normal feeding/fasted vs. massive overfeeding states) serve a purpose of generating heat, and heat is not a mere "waste product" in a warm-blooded creature ... one that ceases to live if its temperature drops too low.  Living organisms do possess intricate regulatory systems for fuel partitioning and energy usage.

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.

He's right about one thing here, living organisms do have more or less intricate systems to determine what we use the energy harnessed from our intake to do at any given time.  The human body will, to some degree compensate depending on the urgency:  I'm guessing we're not expending much energy to build muscle protein when hypothermia is setting in.  Just a wild guess there.  But to determine the CO for thermal vs. other expenditures does not require entropy considerations.  This is a fundamental error in McLeod's thinking here.  Thermal energy out is a perfectly valid "out" term in TFLOT ... but I'm repeating myself.


Bottom line:  TFLOT is perfectly applicable to humans.