A calorie is what? Part 2
Calories-in calories-out (CICO) in one hundred bullet points - 1
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The following post (edited) was in response to Adam Kosloff’s post at Farmer Versus Banker, mirrored here:
My answer: Let me help you with the CICO problem. I got into nutrition as a research activity exactly over this issue. I think the whole controversy was started by an emotional reaction to the suggestion that the Atkins diet offered a “metabolic advantage” in weight loss. The intellectual level of the ensuing discussion was not encouraging. As you described there were no established standards.
I will just lay out the POV that I and my colleagues think explains the problem. The format will be distinct bullet points which may be assembled -- or may self-assemble — later into a consistent narrative. I will start here and mirror to my Substack and continue there and, if you like, copy here.
Previous Substack posts on the subject:
https://richardfeinman.substack.com/p/a-calorie-is-what
• A calorie is what?
Calories-in calories-out, diets, thermodynamics and all that - 1
https://richardfeinman.substack.com/p/illustrations-from-the-first-edition
• Illustrations from the first edition and from my blog.
The art of science. The science of art - 1.
https://richardfeinman.substack.com/p/calories-in-calories-out-substrate
• Calories-in-calories-out, substrate cycles and diesel engines
The bottom line:
We don’t eat calories. We eat food which is converted to other metabolites. There is, as in all chemical reactions, an associated energy. Key idea: the energy is in the reaction, not the reactants and products.
Generally, we don’t really know what the reactions are. Key idea: energy “in” is after digestion and processing. We don’t know calories in (CI). And, it follows that we don’t know CO either.
The Atwater values (CHO = 4 kcal/g, etc.) is the value for the complete oxidation (reaction) in oxygen in the calorimeter and is meant as convenient number for comparison but has no meaning in detail (except for that particular reaction).
The problem is discussed in terms of thermodynamics which more or less predicts variable energy of digestion and metabolism for different diets. In practice, there is mostly not big variation except for unusual, therapeutic or special diets. That is what has to be explained. “ Energy balance” is due to biology — extensive feedback systems — not to any thermodynamic principles.
Background
The issue arises from the question of whether two isocaloric diets of different macronutrient composition may produce different changes in body mass or body fat. The most common targets are diets based on carbohydrate restriction ( low-carbohydrate, ketogenic, carnivore). Historically referred to as “metabolic advantage” of the Atkins diet.
The effect is seen experimentally in numerous comparisons. It does not always happen. But it is evident in many cases. The key objections from critics have been:
The data are wrong. The experiments were not done correctly.
The data are wrong. Experiments may seem okay but it is theoretically impossible because it would violate the laws of thermodynamics. (Usually, the first law is meant or implied — this is embodied in phrase “calories-in-calories-out,” or CICO).
I address only the second one specifically. If the second point were correct, that would be the end of it.
Most chemists and even some physicists are modest about expertise in thermodynamics. I have studied it, written a few papers and teach aspects of thermodynamics. Most of the objections are incorrect and have fatal errors. However, even the problem needs to be better defined.
Experimentally, balance (I will use this instead of CICO) as the general effect. We all eat different meals of at least some difference in size and composition. Our weight is generally stable within a moderate range of age and general health. On some therapeutic diets or those of unusual composition, this breaks down. Now you may see greater or lesser changes in body mass than what was predicted from caloric composition. These changes can be substantial are are the backbone of many diet strategies.
Chemical thermodynamics.
Thermodynamics is about heat and work. The field is sophisticated, that is, mathematical, but its origins and its persistent use is how to do work efficiently.
Chemical reactions are associated with an energy of reaction. Some reactions require energy to be added in order to proceed (endergonic reactions).
Some chemical reactions (exergonic) give off energy.
The energy is in the reaction not the reactants and products.
Thermodynamics, misunderstandings and misuse of terms.
Calorie is a unit of energy. You do not eat energy. You eat mass. You eat grams, ounces, lbs., etc. Grams of food are converted to grams of products in a biochemical reaction. How much?
Different foods will be converted to different products and produce different energies. It depends on the conditions and the state of the organism.
Key idea: We don’t really know “calories in.”
Chemical reactions consume or produce energy. The energy is in the reaction not in the reactants and products.
So what is the 4 kcal (kilo) for carbohydrate in the nutrition tables? It’s a shorthand way of comparing reactions. It means that if you completely oxidize a gram of carbohydrate with oxygen in the calorimeter, you will produce 4 kilocalories of energy. The energy appears as heat. If you do any other reaction, all bets are off.
Reading Gary Taubes’ discussion of pre-insulin type-1 diabetics wasting away despite eating well convinced me CICO is too simplistic. Maybe “CICO plus the endocrine environment”?
Thanks, Richard. I love reading your insights into the CICO model because you have twin expertise in thermo AND in the practical therapeutic benefits of these "metabolically advantageous" diets. I can share on my Sub (for whatever that's worth!) but need some time to process and sort through all the ideas (and posts you linked to). The reasoning all sounds solid, if the bio chem and physics are above my paygrade.
This point in particular seems powerful and impervious to counter: "Generally, we don’t know what the reactions are. Key idea: energy “in” is after digestion and processing. We don’t know calories in (CI). And, it follows that we don’t know CO either."