Metabolic advantage, “a calorie is a calorie,” and why the First Law of Thermodynamics does not apply.

Posted: June 6, 2011 in low-carbohydrate diet, The Nutrition Story, thermodynamics
Tags: , , , ,


The big news in the low carb world is that Consumer Reports has published, for the first time, faint praise for the Atkins diet. However, the vision one might have of CR employees testing running shoes on treadmills doesn’t really apply here. They did not put anybody on a diet, even for a day. They didn’t have to. They have the standards from the government. Conform to the USDA Guidelines and CR will give you thumbs up. It probably doesn’t matter since, these days, most people buy a food processor by checking out the reviews on the internet — there are now many reviews online of what it’s like to actually be on a low-carbohydrate diet, so rather than follow CR’s imaginings of what it’s like, you can check out what users say — Jimmy Moore, Tom Naughton and Laura Dolson together get about 1.5 million posts per month with many tests and best buy recommendations. What caught my eye, though, is the ubiquitous Dean Ornish; the ratio of words written about the Ornish diet to the number of people who actually use it is probably closing in on a googol (as it was originally spelled). The article says: “to lose weight, you have to burn up more calories than you take in, no matter what kind of diet you’re on. ‘The first law of thermodynamics still applies,’ says Dean Ornish, M.D.

That’s how I got into this field. My colleague Gene Fine, and I published our first papers in nutrition on the subject of metabolic advantage and thermodynamics and we gave ourselves credit for reducing the number of people invoking laws of thermodynamics. “Metabolic advantage” refers to the idea that you can lose more weight, calorie-for-calorie on a particular diet, usually a low-carbohydrate diet. (The term was used in a paper by Browning to mean the benefits in lipid metabolism of a low-carbohydrate diet, but in nutrition you can re-define anything you want and you don’t have to cite anybody else’s work if you don’t want to). The idea of metabolic advantage stands in opposition to the idea that “a calorie is a calorie” which is, of course, the backbone of establishment nutrition and all our woe. As in the CR article, whenever the data show that a low-carbohydrate diet is more effective for weight loss, somebody always jumps in to say that it would violate the laws of thermodynamics. Those of us who have studied or use thermodynamics recognize that it is a rather difficult subject — somebody called it the physics of partial differential equations — and we’re amazed at how many experts have popped up in the nutrition field.

Finding the right diet doesn’t require knowing much thermodynamics but it is an interesting subject and so I’ll try to explain what it is about and how it’s used in biochemistry. The physics of heat, work and energy, thermodynamics was developed in the nineteenth century in the context of the industrial revolution — how efficiently you could make a steam engine operate was a big deal.  Described by Prigogine as the first revolutionary science, it has some interesting twists and intellectual connections. The key revolutionary concept is embodied tin the second law which describes the efficiency of physical processes.  It has broad philosophical meaning.  The primary concept, the entropy, is also used in communication and  the content of messages in information theory.  The entropy of a message is, in one context, how much a message has been garbled in transmission.  The history of thermodynamics also has some very strange characters, besides me and Gene, so I will try to describe them too.

First, we can settle the question of metabolic advantage, or more precisely, energy inefficiency. The question is whether all of the calories in food are available for weight gain or loss (or exercise) regardless of the composition of the diet. Right off, metabolic advantage is an inherent property of higher protein diets and low carbohydrate diets. In the first case, the thermic effect of feeding (TEF) is a measure of how many of the calories in food are wasted in the process of digestion, absorption, low-level chemical transformation, etc. TEF (old name: specific dynamic action) is well known and well studied. Nobody disputes that the TEF can be substantial for protein, typically 20 % of calories. It is much less for carbohydrate and still less for fat. So, substituting any protein for either of the other macronutrients will lead to energy inefficiency (the calories will be wasted as heat). A second unambiguous point is that in the case of low-carbohydrate diets, in order to maintain blood glucose, the process of gluconeogenesis is required. You learn in biochemistry courses that it requires a good deal of energy to convert protein (the major source for gluconeogenesis) into glucose.

So, right off, metabolic advantage or energy inefficiency is known and measurable. Critics of carb restriction as a strategy admit that it occurs but say that it is too small in a practical sense to be worth considering when you are trying to lose weight. These are usually the same people who tell you that the best way to lose weight is through accumulation of small changes in daily weight loss by reducing 100 kcal a day or something like that. In any case, there is a big difference between things that are not practical or have only small effects and things that are theoretically impossible. If metabolic advantage were really impossible theoretically, that would be it. We could stop looking for the best diet and only calories would count. Since we know energy inefficiency is possible and measurable, shouldn’t we be trying to maximize it.  But what is the story on thermodynamics? What is it? Why do people think that metabolic advantage violates thermodynamics? What is their mistake? More specifically, doesn’t the first law of thermodynamics say that calories are conserved? Well, there is more than one law of thermodynamics and even the first law has to be applied correctly. Let me explain. (Note in passing that the dietary calorie is a physical kilocalorie (kcal; 1000 calories).

There are four laws of thermodynamics. Two are technical. The zeroth law says, in essence, that if two bodies have the same temperature as a third, they have the same temperature as each other. This sounds obvious but, in fact, it is an observational law — it always turns out that way. The law is necessary to make sure everything else is for real. If anybody ever finds an experimental case where it is not true, the whole business will come crashing down. The third law describes what happens at the special condition known as the absolute zero of temperature. In essence, the zeroth and third laws, allow everything else to be calculated and practical thermodynamics like bioenergetics pretty much assumes it in the background.

The second law is what thermodynamics is really about — it was actually formulated before the first law — but since the first law is usually invoked in nutrition, let’s consider this first. The first law is the conservation of energy law. Here’s how it works: thermodynamics considers systems and surroundings. The thing that you are interested in — living system, a single cell, a machine, whatever, is called the system — everything outside is the surroundings or environment. The first law says that any energy lost by the system must be gained by the environment and any energy taken up by the system must have come from the environment. Its application to chemical systems, which is what applies to nutrition, is that we can attribute to chemical systems, a so-called internal energy, usually written with symbol U (so as not to confuse it with the electrical potential, E). In thermodynamics, you usually look at changes, and the first law says that you can calculate ΔU, the change in U of a system, by adding up the changes in heat added to the system and work done by the system (you can see the roots of thermo in heat machines: we add heat and get work). In chemical systems, the energy can also change due to chemical reactions. Still, if you add up all the changes in the system plus the environment, all the heat, work and chemical changes, the energy is neither created nor destroyed. It is conserved.

Now, why doesn’t the first law apply to nutrition the way Ornish thinks it does? To understand this, you have to know what is done in chemical thermodynamics and bioenergetics, (thermo applied to living systems). If you want to. In nutrition, you can make up your own stuff. But, if you want to do what is done in chemical thermodynamics, you focus on the system itself, not the system plus the environment. So, from the standpoint of chemical thermodynamics, the calories in food represent the heat generated by complete oxidation of food in a calorimeter.

In a calorimeter, the food is placed in a small container with oxygen under pressure and ignited. The heat generated is determined from the increase in temperature of the water bath. (Before the food measurement, we determine the heat capacity of the water bath, that is, how much heat it takes to raise the temperature). The heat is how we define the calories in the food. The box around the sample in the figure shows that we are measuring the heat produced by the system, not the system plus the environment, that is, not applying the first law. If you applied the first law, the calories associated with the food would be zero, because any heat lost in combustion of the food would show up in the water bath of the calorimeter. The calories per gram of carbohydrate would be 0 instead of 4, the calories per gram of fat would be 0 not 9, etc. So, in studying reactions in chemical thermodynamics, energy is not conserved, it is dissipated. When systems dissipate energy, the change is indicated with a minus sign, so for oxidation of food, generally: ΔU < 0. So, no, the first law does not apply. That’s one of the reasons that “a calorie is not a calorie.”
There is an additional point that we assumed in passing. In chemical thermodynamics, the energy goes with the reaction, not with the food. It is not like particle physics where we give the mass of a particle in electron-volts, a measure of energy, because of E=mc2. What this means, practically, is that the 4 kcal per gram of carbohydrate is for the reaction of complete oxidation. Do anything else, make DNA, make protein and all bets are off.
The bottom line is that, contrary to what is usually said, thermodynamics does not predict energy balance and we should not be surprised when one diet is more or less efficient than another. In fact, the question to be answered is why energy balance is ever found. “A calories is a calorie” is frequently what is observed (although there is always a question as to how we make the measurement). The answer is that insofar as there is energy balance, it is a question of the unique behavior of living systems, not physical laws. Two similar subjects of similar age and genetic make-up may, under the right conditions, respond to different diets so that most of what they do is oxidize food and the contributions of DNA or protein synthesis, growth, etc. may be similar and may cancel out so that the major contribution to energy exchange is the heat of combustion.
But thermodynamics is really not about the first law which, while its history is a little odd, it is not revolutionary. Intellectually, the first law is related to conservation of matter. Thermodynamics is about the second law. The second law says that there is a physical parameter, called the entropy, almost always written S, and the change in entropy, ΔS, in any real process, always increases. In ideal, theoretical processes, ΔS may be zero, but it never goes down. In other words, looking at the universe, (any system and its surroundings), energy is conserved but entropy increases. The first law is a conservation law but the second law is a dissipation law. We identify the entropy with the organization, order or information in a system. Systems proceed naturally to the most probable state. In one of the best popular introductions to the subjects, von Baeyer’s Warmth Disperses and Time Passes, entropy is described in terms of the evolution of the organization of his teenage daughter’s room.  To finish up on calorimeters, though, there is Lavoisier’s whole animal calorimeter.

One of Lavoisier’s great contributions was to show that combustion was due to a combination with oxygen rather than the release of a substance, then known as the phlogiston. Lavoisier had the insight that in an animal, the combination of oxygen with food to produce carbon dioxide was the same kind of process. The whole animal calorimeter was a clever way to show this. The animal is placed in the basket compartment f. The inner jacket, b, is packed with ice. The outer jacket, a, is also packed with ice to keep the inner jacket, cold. The heat generated by the animal melts the ice in the inner jacket which is collected in container, Fig 8. Lavoisier showed that the amount of carbon dioxide formed was proportional to the heat generated as it would be if an animal were carrying out the same chemical reactions that occur, for example, in burning of charcoal. “La vie est donc une combustion.” His collaborator in this experiment was the famous mathematician Laplace and people sometimes wonder how he got a serious mathematician like Laplace to work on what is, well, nutrition. It seems likely that it was because Laplace owed him a lot of money.

Comments
  1. David Boothman says:

    Here is an example of claimed metabolism modification to increase energy efficiency in athletes

    http://jp.physoc.org/content/589/4/963.abstract?sid=99c0b4d4-bbb9-4c77-a217-fef2f86177e6

  2. Dave says:

    Thanks for tackling a difficult topic. I’ve started down this road three times on my blog, never got a presentation I liked. I’ll add some thoughts since you got the ball rolling.

    I don’t think the Zeroth Law is observational, rather it is a definition that enables observation. Otherwise I don’t think temperature or thermal equilibrium have any meaning, and without the Zeroth Law you couldn’t have a thermometer, since in order to give a meaningful measurement, the thermometer must be at thermal equilibrium with the system being measured. Further, the thermometer (and the whole notion of temperature) isn’t very useful if it gives different readings for systems in thermal equilibrium with each other. I don’t think you could do an experiment which violates the Zeroth Law, because the Zeroth Law defines thermal equilibrium and temperature in terms of each other.

    The Third Law defines the zero of the temperature scale. This point is special because it corresponds to the minimum of the entropy. Why does entropy have an absolute minimum? Entropy is the “state function” for thermodynamic systems, encoding our limited information (or large uncertainty) about the microstate (e.g. individual position and velocities of each atom) as a function of the macroscopic quantities we measure, like temperature, volume, and pressure. When entropy is at a minimum, it means you know (or in principle could know) everything about the detailed microstate of the system, given the macroscopic observations. So if all of the atoms in a system were perfectly still with zero velocity, you could (in principle) know the exact microscopic state. Since you can’t know more than everything about a system, entropy has an absolute minimum, and it’s useful to define the zero of temperature as corresponding to this state.

    That dove-tails nicely with the Second Law. Note that the Second Law is the only true “law” in the sense of always being true, because it is a mathematical result. What it basically says is you can’t increase your knowledge about the internal microscopic state of a closed system. This isn’t really about disorder per se, at least not in the non-technical sense of disorder. Take the messy room example. You tell your daughter to clean her room, and she puts everything in its place, then shuts the door. Once she locks herself in there, the best possible scenario is that she doesn’t move anything, but this is unlikely: assuming “a place for everything and everything in its place” (only one state corresponding to “clean”), it is much more likely that things will get messy in a way that you can’t predict, i.e. she’ll take a book from the bookshelf and leave it on the floor someplace. But you can’t know that unless you open the door, in which case the system would no longer be closed. As long as the door remains closed, your knowledge of what’s where in her room decreases, hence the entropy increases. But once you open the door, you know the exact state of the room (whether messy or clean), and entropy returns to a minimum.

    So the Second Law could be viewed (at least in part) as defining what is meant by a closed system, one in which we gain no new information about the internal state regardless of what happens “inside the box”.

    The First Law is the observational law. Mathematically, the conservation of energy is derived from an underlying symmetry in the equations we use to model physical phenomena. The relevant symmetry is in time-translation, and basically says “if the laws of physics are the same later as they are now, energy will be conserved”. The First Law is not true in general, say in the vicinity of a small black hole (where spacetime curvature is significant), or for the universe as a whole (due to the expansion of spacetime). But most people don’t diet near black holes, the local universe is observed to be extremely flat, and so the First Law can be taken to be true as an excellent approximation.

    With all of that in mind, we can see that biological organisms are entropy factories. When you eat some food, your body tears it all apart (entropy goes up), but in a lot of cases then reorganizes the resultant atoms in a predictable way, like building DNA. The Second Law tells us that if the entropy in a part of a closed system (you) decreases, then the entropy in the rest of the system (the Universe) must increase by more. And this is what we see, where the added entropy is largely in the form of the heat radiated by the body. The First Law tells us that whatever energy is used in building DNA (or whatever other organized structures) plus that lost in heat to satisfy the Second Law had to come from someplace. None of this further precludes mechanisms that waste heat with doing no work, like mitochondrial decoupling.

    So paraphrasing your point, there’s no way a “calorie is a calorie” when discussing biological systems. That organisms maintain low entropy (which is ultimately the process of life; high entropy = dead) means that they necessarily increase the entropy of the universe by losing energy to their surroundings. It follows nicely from your aphorism “you aren’t what you eat, you are what your body does with what you eat”.

    Bit of a mind-bender talking physics with Richard Feinman, so nearly Richard Feynman… :-)

  3. rdfeinman says:

    Thanks for your reply. You raise a number of interesting points… beyond discussion in this venue but maybe in private … Gene Fine and I always say that after working on this problem for a while, we realized that we were studying philosophy which we had made fun of in college. Most of us have the experience that when we study thermodynamics, we have to get the problem sets done and the real meaning we will get to when we are older.

    Looking ahead on the blog, future posts will consider that the second law predicts variable efficiency. This is another reason that we don’t expect energy balance. The real answer, though, is, as you hinted at, thermodynamics is not the question, or at least equilibrium thermodynamics is not. Kinetics or nonequilibrium thermodynamics (which includes kinetics) is the appropriate discipline.

    Life runs on enzymes, that is, on rates. Fat stored in an adipocyte, for example, is at high energy compared to free fatty acids but that energy is never released (on a biological time scale) if the lipolytic enzymes are not active. The enzymes are controlled by hormones and other metabolites — this is where the importance of insulin comes in. We tried to discuss this in a paper in Theoretical Biology and Medical Modeling, available without subscription at: http://www.tbiomed.com/content/pdf/1742-4682-4-27.pdf
    Nonequilibrium thermodynamics is not a well developed field and we didn’t really nail it but Figure 1 of that paper shows the idea.
    RDF

    • Dave says:

      Hi Dr. Feinman. Thanks for the link, read this paper when it originally came out, seems like a good time to take another look as I’ve been noodling around the topic.

      I like your point about “life runs on rates”. That makes for interesting thinking about evolution. How much of evolution is just diddling relative rates by small mutations to the genes that make enzymes?

      • David Boothman says:

        and possibly epigenetic methylation etc. results in rapid response to environmental change through rate variation. The problem is some of these adaptations appear to be heritable and so adverse ones brought about by a novel diet may propagate to the next generation

      • rdfeinman says:

        Not exactly sure what you mean but small mutations can lead to big changes in rates.

  4. PhilT says:

    “If you applied the first law, the calories associated with the food would be zero, because any heat lost in combustion of the food would show up in the water bath of the calorimeter. ”

    don’t understand.

    Before ignition you have the enthalpy of the cold bath & food and the calorific value of the food
    After ignition you have the enthalpy of the warm bath and the products of combustion of the food

    Take the difference between the enthalpy of the warm and cold bath and you have the enthalpy of combustion of the food, which is what you were trying to measure. This neither violates the first law nor demonstrates that the calorific value of the food was zero. The enthalpy of the food may be zero if the bath and food is initially at the reference temperature, but it’s potential energy as calorific value isn’t zero.

    I have yet to see anything in nutrition that violates the first law *providing* everything is measured correctly. The thermic effect of different foods is measurable and real, sure enough, but it complies with the first law.

    • rdfeinman says:

      Nothing violates the first law. The application of the first law to chemical systems, however, involves measuring the internal energy change (or enthalpy) in the calorimeter. What is determined is, as you say “the enthalpy of combustion of the food, which is what you were trying to measure.” This is approximately the free energy of reaction which tells you about the tendency of the chemical reaction to go forward. It is energy that is dissipated (picked up by the calorimeter or, in a applied system, providing energy for some other chemical reaction).

      In chemical thermodynamics, we look at the combined first and second laws as applied to reaction in a particular direction. It is true that many thermodynamics texts don’t say this explicitly although many do:

      Levine (Physical Chemistry, 3rd ed., McGraw-Hill, p. 110):
      “It is usually most convenient to deal with properties of the system and not have to worry about changes in the thermodynamic properties of the surroundings as well. Thus, although the criterion for material equilibrium is perfectly valid in general, it will be more useful to have a criterion for material equilibrium that refers only to thermodynamic properties of the system itself.”

      A statement that is more complicated but that directly addresses your comment is in Smith EB: Basic Chemical Thermodynamics, 5th edn. Imperial College Press; 2004:
      “Since a system and its surroundings taken together could be regarded as a new system whose energy is constant, the position which leads to the maximum entropy for system and surrounding is the equilibrium position. However, it is more convenient to have a definition of the position of equilibrium which can be expressed in terms of the properties of the system alone and which does not require knowledge of changes taking place in the surroundings (p. 36).”

      The real point is that people who invoke the first law to say that metabolic advantage is not possible are not trying to get at the answer but rather simply trying to avoid bending their mind beyond “a calorie is a calorie.” Nobody knows the extent to which metabolic advantage exists but if you think it is impossible, you won’t try to find out what its potential is. So when it is demonstrated, even anecdotally, it may be inaccurate or wrong but there is no inherent reason to assume that the observation is incorrect. For many people, weight gain and loss is a very serious problem so it makes sense to see what the potential is in the insulin-control idea.

      “I don’t understand. I went to this conference and they had these elaborate buffets and I really pigged out on lobster and roast beef and I didn’t gain any weight.” Did you ever hear anybody say that about pasta?

  5. […] From Dr. Richard Feinman: If you don’t understand how the first law of thermodynamics works in a human body, shaddup abo…. […]

  6. […] Very interesting read by Dr. Richard Feinman regarding the perception of calories. […]

  7. Dave Dixon says:

    Nice discussion of thermodynamic entropy here: http://secondlaw.oxy.edu/

  8. Dave Dixon says:

    Great quote from the site above, highly relevant to the “calorie is a calorie” discussion:

    The universe as we know it is therefore as much controlled by the laws of chemical dynamics as by the laws of thermodynamics.

  9. […] the First Law of Thermodynamics does not apply. August 29, 2011By: rdfeinman Read the Full Post at: Richard David Feinman The big news in the low carb world is that Consumer Reports has, for the first time, faint praise […]

  10. Naught says:

    I’ve always thought it odd that the “a calorie is a calorie” people are using arguments about conservation of energy to support statements that are actually about conservation of mass. A kilo-calorie doesn’t weigh very much (0.0000000000000466 grams), so what they actually mean is that certain energy uses of the body are associated with certain inputs and outputs of body mass. But, as the good doctor points out, that’s a heck of a lot more complicated than just “a calorie is a calorie.”

  11. Anastasio Rossi says:

    Given: If a checking account is receiving more money than it is paying out, its balance will increase. If it receiving less money than it is paying out, its balance will shrink.

    Given: If a car burns gasoline faster than it is getting gasoline, it will eventually stop running.

    Similarly, if a human body burns calories faster than it is receiving calories, it will eventually lose weight as it begins to consume stored fat and other body tissues.

    This concept is the basis for those who support “a calorie is a calorie”, and Dean Ornish’s statement that, “to lose weight, you have to burn up more calories than you take in, no matter what kind of diet you’re on.”

    Doesn’t this cut through all the theories, arguments, and articles involving Laws of Thermodynamics, carbs vs fat vs protein, effects of body metabolism, etc., and boil down to weight loss/gain ultimately being a function of “calories in, calories out (including ‘wasted calories’)?

    • rdfeinman says:

      Given: If a checking account is receiving more money than it is paying out, its balance will increase. If it receiving less money than it is paying out, its balance will shrink.

      If the bank takes a fee (thermic effect of feeding, substrate cycling, NEAT), you will be pissed when you see your bank statement.

      >Given: If a car burns gasoline faster than it is getting gasoline, it will eventually stop running.

      If it is a racing car and it is not getting high test gasoline, it may stop running sooner than you thought.

      Similarly, if a human body burns calories faster than it is receiving calories, it will eventually lose weight as it begins to consume stored fat and other body tissues.

      You’ve slipped in the assumption that all calories are the same, no bank fees, no difference in high-test performance.

      This concept is the basis for those who support “a calorie is a calorie”, and Dean Ornish’s statement that, “to lose weight, you have to burn up more calories than you take in, no matter what kind of diet you’re on.”

      Having slipped in the assumption that “a calorie is a calorie,” you are guaranteed to come to the conclusion that “a calorie is a calorie.”

      Doesn’t this cut through all the theories, arguments, and articles involving Laws of Thermodynamics, carbs vs fat vs protein, effects of body metabolism, etc., and boil down to weight loss/gain ultimately being a function of “calories in, calories out (including ‘wasted calories’)?

      Wasted calories are just what we are shooting for. People on low carb diets are happy with the feeling that they are wasting some of the calories that they take in. So, yeah, if you count wasted calories, CICO is true but meaningless. Those of us who have actually studied thermodynamics know that the first step is to be very careful about defining “in” and “out,” that is, system and environment.

      Are people on a low carb diet really using their calories less efficiently (efficiency from the point of fat storage)? There are many arguments about this but my experience is that you don’t get good discussions on this issue , so I’ll tell you what is not conjecture:
      1) There is nothing in thermodynamics that says all macronutrients should be metabolized with equal efficiency, so it is possible. The key part of thermodynamics is not the first law, but the second law which says: Calories (per unit temperature) into the system is always less than or equal to calories out of the system. Calories in, calories out is generally not true. Nothing cuts through the second law (so far).
      2) For the studies showing that people gain less weight on a low carbohydrate diet compared to a low fat diet to be in error due to inaccurate diet records, requires that the low fat people under-report their calories, or the low-carb people over-report their calories or both. While not impossible, practically speaking, it might be good to be on a diet where you think you are eating more than you actually are.

      Do you accept this answer?

    • David says:

      A nice analogy, now why not carry through with it. Next time you fill up why not put diesel in your tank, lots of calories there. The calorie is a calorie doctrine could have been created by the dog food industry. A number of ingredients in dog food, through generalization of names of ingredients e.g. animal byproduct, hide the fact that some ingredients such as feathers beaks and claws are barely digestible however their protein, fat and carbohydrate content are included in the claimed analysis. The first law of thermodynamics is but one factor controlling calorie absorption. This is also why the feces of some species provide a high energy food source for other species, e.g. canine cat litter box grazing. There is a reason why Engineering is often referred to as Applied Science. It applies the fundamental laws of science taking into account that most systems are open and that usually more than one law is operating at a time considering the resulting inefficiencies of their interaction. Thermodynamics in the real world is usually an applied science and human metabolism could be considered the study of the engineering of the human bio-system, and far more complex and adaptable than any human creation to date because evolution had more time.

  12. Anastasio Rossi says:

    In spite of all the talk to the contrary, it does not take a rocket scientist to understand this: If your body uses more energy than it is taking in, eventually it must begin to utilize energy available in the form of fat and other tissue. When this energy source is depleted without being replaced, the result is a loss of weight. You can digress ad infinitum and ad nauseam, with fancy talk about Thermodynamics, rates of metabolism, different types of calories, and system/environment scenarios, but the above statement remains immutable.

    • rdfeinman says:

      It certainly makes sense as you write it. So what is it that you think I am saying that is in contradiction. I am not a rocket scientist but, for a chemist, I am middling smart and I certainly give this some thought. So what do you think that I am saying that is in contradiction?

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