Heat, Entropy & Thermogenesis
A summary post of ideas here, that I've likely stated elsewhere on the blog but wanted to gather in one place.
Last week on Facebook, to the detriment of his credentials and credibility, Jason Boehm posted and deleted a post about calories and the Second Law of Thermo. I queried what it had to do with the original point which was more of a 500 cals spinach vs. 500 cals Coke type nonsense, so he did address that in a second FB post that stands (minus lots of relevant input from people he deleted, labeled hateful and pretty much had a kitten over ... nobody called him a moron BTW, that's a clever tactic of those that can't hold up their end of an intellectual debate on the science ... can't leave the self-incriminating evidence). But I digress.
Well, in the post on the Second Law of Thermo, Jason referenced a 2007 blog post on that topic by Dr. Eades. It is one I had not seen before: Thermodynamics and weight loss. Eades writes:
The second law of thermodynamics says that the entropy of the universe increases during any spontaneous process.
Warning ... bullsheet about to follow because while this is considered true of the entire universe, it is not applicable to the chemical reactions he's talking about. A spontaneous reaction requires only a net negative change in free energy (-∆G). Entropy can increase (+∆S) so long as the combined changes in enthalpy (∆H) and entropy result in a negative change in free energy according to the relationship: ∆G = ∆H - T∆S. Eades goes on ad nauseum, quoting scientists that go by "Sir", all of which makes him sound knowledgeable. But he's really not, at least about this subject. Eades writes The First Law to include a Second Law term:
calories in = calories out + entropy
He goes on to do a little calculation where 100 calories in = 70 calories out + entropy, thus entropy is 30 calories. It is evident that Eades is equating entropy with heat generated ... and "lost" ... when he cites Postprandial Thermogenesis Is Increased 100% on a High-Protein, Low-Fat Diet versus a High-Carbohydrate, Low-Fat Diet in Healthy, Young Women in the context of weight loss. This is the same argument put forth in the abominable Feinman-Fine paper. TSLOT doesn't violate TFLOT! They are saying that the TEF term on the right side of the energy balance equation (cue Lyle) is entropy. They are wrong. The equation above should perhaps read: calories in = calories out doing mechanical and chemical work + heat calories out.
To reiterate once again: Heat evolved in a chemical reaction is a perfectly appropriate "calories out" First Law term. Period.
- aka Heat -
Is NOT Entropy
Now, Eric Jequier and others have established thermogenic factors for the macronutrients ... used in the Double-F paper ... the averages being 2.5%, 7% and 27.5% for fats, carbs and protein respectively. Every time I address this, I feel the need to point out the dishonesty of the LC community for their "low fat makes you fat" nonsense, because carbs are MORE thermogenic, by a factor of almost 3X, than fat! You need to alter protein to come out ahead. Still, that 27.5% sounds awfully magical, doesn't it? I do believe that early on in a switch to a high protein diet, there is somewhat of a First Law wasting effect that goes on. I also think that like other metabolic "shocks" to the system, this is fleeting and the body adapts.
But ... but ... thermogenesis! We can see "calories out" go up after a meal, and they go up moreso with a high protein meal. True! But ....
I have a relatively small kitchen in this old home I inhabit these days. I heat it, when I do, with a small, thermostat controlled, electric unit in the colder months. If it's around 30 degrees outside, and I have the thermostat set at 65 degrees, that heater is on for long periods consuming a fair amount of electricity. If I'm in the kitchen boiling up a couple of pots of paleo bone broth whilst roasting wild boar jowls and chitterlings in my oven, the heater only comes on for short periods. Why? Because all of the hot steam or heat that escapes the oven -- especially when I do my gut check, grin -- is "waste" to my stove/oven, but it contributes to the heat in the room, thus lessening the burden on my heater. While the heat from the stove/oven represents inefficiency of the electrical energy that I pump into the burners to warm, denature, melt and char my food ... aka ... cook, it is not all that inefficient in the overall picture. The "waste" keeps my kitchen warmer so the heater doesn't have to. In other words, the thermogenic "waste" from my stove reduces the need for thermogenesis from my heater. The portion of my electric bill that goes towards heating doesn't change, it just came from different appliances.
A warm blooded organism, like us humans, is sort-of like my kitchen only our thermostats must be set in a narrow range centered just shy of 99 °F. Fall below 95 or rise above around 104 and it becomes life threatening, normal is 98-100, exist just outside those bounds and your metabolism is likely not functioning optimally. If you consume a more thermogenic fuel, more obligate heat is produced. For protein, let's use an Eades'-inspired high end estimate for protein, 30%: Consume 100 calories of protein and 30 calories of heat are produced. This adds to the heat from a variety of sources and other reactions in the body to keep your temperature in the 98-100 range. But ultimately your thermostat is hooked to UCP's and/or so-called "futile cycles" (see for example my post on DNL in skeletal muscle to waste excess carbs). These are our bio-electrochemical heaters. These heaters are simply used less when the body is kept warm by heat generated in the course of "cooking" going on elsewhere ... like protein thermogenesis (and all TEF). The thermogenic "waste" from TEF reduces the need for thermogenesis from my mitochondria and futile cycles.