8 ms·

“A calorie is a calorie” violates the second law of thermodynamics (2004)

73 points by wrycoder 5y ago

EamonnMR 5y ago
Absolutely hyperbolic title. Sure, "A calorie cannot exceed a calorie" is more correct, but it's less punchy so nobody uses it. The point is that you can't get free energy from nowhere. It's very well illustrated by DNP: https://en.wikipedia.org/wiki/2,4-Dinitrophenol https://en.wikipedia.org/wiki/2,4-Dinitrophenol
- cammil 5y ago
  That's not what they are saying.
- bri3d 5y ago
  To many, the point of "a calorie is a calorie" is not that you can't get free energy from nowhere, it's that that diet / food selection is meaningless as food containing one calorie of potential will always evolve to one calorie's worth of metabolic energy through some metabolic process or another - as in the abstract, that two "isocaloric" diets will always produce the same results. The idea of the paper is to dispel this notion.
  - gamblor956 5y ago
    The point of the article is that this is not true. Chemically, a calorie is a calorie. But one calorie of fat is metabolically different from the equivalent caloric value of protein, because food is not processed by the body the same way that a calorie is measured.
    - NikolaeVarius 5y ago
      It doesn't matter. If I eat nothing but 500 calories of Twinkies/cake/pure sugar (as measured on the label) every single day, I guarantee I will lose weight. Literally no amount of hand wringing will change that fact
      - CydeWeys 5y ago
        This is a strawman rebuttal. That's not remotely what the person you're replying to said.
      - KoftaBob 5y ago
        The debate around "A calorie is a calorie" relates to the whole "calories in vs calories out" concept for weight loss/gain. Examples like yours focus heavily on the "calories in", but forget to consider the "calories out" aspect. What I mean there is, when someone says that the body processes different macronutriets differently, a lot of that has to do with how it affects "calories out" If you eat 500 calories of a food that your body will only process a small amount of, and expel the other 450 calories as waste, that 450 is part of the "calories out". That's only a net "calories in" of 50. On the other hand, if you eat 500 calories of a food that your body chooses to process/store most of, that's 400 calories in, and only 100 calories out. The calories out part of the equation isn't just the energy you expend per day through movement/metabolic processes/etc, it's also the calories that are expelled as waste because the body didn't store that macronutrient.
        josephcsible 5y ago
        > If you eat 500 calories of a food that your body will only process a small amount of, and expel the other 450 calories as waste Does this much lack of absorption ever actually happen, though, outside of exceptional cases like if you get food poisoning?
        KoftaBob 5y ago
        I used an exaggerated ratio to drive the point home. To clarify, I'm not talking as much about absorption, more-so about things like how a macronutrient affects insulin sensitivity. Carbohydrates decrease insulin sensitivity more than protein and unsaturated fats would. Decreased insulin sensitivity means increased insulin resistance. "Having insulin resistance means that the walls of the cells within the body that need to take in glucose for energy, have a much-lowered sensitivity to insulin. This makes it harder for the cells to receive the necessary glucose through the cell wall. That glucose then remains in the bloodstream, resulting in high blood sugar levels, which the liver then has to manage. When this excess sugar reaches the liver, it is converted to fat. The fat cells leave the liver via the bloodstream and cause weight gain. If left unmanaged this can lead to obesity."
  - dahfizz 5y ago
    This smells like a straw man. From the article: > it is important to understand exactly what it is meant by "a calorie is a calorie." The most common meaning is that is it impossible for two isocaloric diets to lead to different weight loss. I think that is hyperbolic - I've never heard that all isocaloric diets are guaranteed to result in the exact same weightloss. The point of "a calorie is a calorie" is that you need to reduce calories to lose weight. From the chart in the article, going from a 10% carb diet to a 50% carb diet (which is a huge change) only results in a effective caloric difference of ~130. It is _much_ simpler and more effective to just skip a 100 cal snack than it is to cut all carbs out of your diet.
    - treeman79 5y ago
      According to math yes. Reality is carbs increase hunger making dieting harder.
      - 0x0nyandesu 5y ago
        That's just in your head not something that is universally true for everyone. In my experience all large quantities of food increase hunger because you get your body used it. With carbs it's just easier to eat more in a smaller amount of space.
      - yufhgyjj 5y ago
        Keto, the Qanon of diets.
      - Retric 5y ago
        I lost weight on a high carb diet and I have lost weight on a low carb diet. Day 2 they felt different, but by day 200 the body adjusts and you get hungry either way. To simplify the body approximates the food in your diet, but also measures the amount of fat you have. A great many things trick the first, but the second doesn’t care what or when you eat. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6039924/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6039924/
    - jerf 5y ago
      This is a common motte & bailey argument. If you press in on "are all foods really the same?", you get "Oh, no, of course there are differences", but as soon as you're not pressing we end up right back at "you just have to cut your calories because all calories are exactly the same and it doesn't matter where they come from". Ironically, you demonstrate this in your last paragraph. If all calories are the same, yeah, just cut 100 out some other way. But if they have different effects on hormones, satiety, any number of other systems, then it may not be "simpler and more effective" to "just" drop 100 calories as a snack. You may need to actually change what you eat.
  - CydeWeys 5y ago
    > it's that that diet / food selection is meaningless as food containing one calorie of potential will always evolve to one calorie's worth of metabolic energy through some metabolic process or another Maybe that's true evolutionarily over tens of millions of years, but it's definitely not true that cellulose calories are remotely equivalent to fat calories -- not unless you're already a ruminant, anyway. Similar issues may present themselves with other types of calories. Just because in theory we could evolve to optimally use all potential sources of energy in food doesn't mean that we actually have yet.
    - Ekaros 5y ago
      Also I believe there is some types of fats that aren't as easily digested. Might be some too that are not at all. Whole system is rather complicated process and don't exactly simplify to equalling same energy you get from burning or is stored in chemical bonds...
  - EamonnMR 5y ago
    You would be surprised how many otherwise serious people have advanced to me the notion that you can get more than a calorie from a calorie of food, mostly in service of the notion that weight loss is impossible and you shouldn't try.
- wrycoder 5y ago
  The article refers to the usage in nutrition science: CICO - "calories in equal calories out". We are learning that this is not the whole truth.
  - kleiba 5y ago
    The notion "a calorie is a calorie", however, refers only to the "CI" part.
  - na85 5y ago
    The problem is it's very poorly understood, even by medical professionals. I had this very argument with an MD who was trying to tell me that if you operate at a sustained caloric deficit you'll eventually stop losing weight. On some level, CICO must be true. Famine is a thing. If you consume a very small but still nonzero amount of calories you will eventually die. So it's not correct to say that "CICO is BS" or anything similar. Whether CICO is an effective way of sustainable weight loss is another conversation.
    - whatshisface 5y ago
      >I had this very argument with an MD who was trying to tell me that if you operate at a sustained caloric deficit you'll eventually stop losing weight. Depending on the definition of "sustained" (I assume the MD meant sustained absolute calories per day, not sustained calories below metabolism) it could be true, because as your body shrinks it reduces its metabolism partly because there is simply less of it.
      - na85 5y ago
        Well then you'd reach a caloric equilibrium and you'd no longer be at a sustained deficit.
    - amelius 5y ago
      It's like in medieval times when someone had a toothache, the tooth was pulled. Because a tooth that is not there can't cause pain. It's physically sound! But then someone said: yeah sure, except perhaps we can be smarter about it.
- joshribakoff 5y ago
  I didn’t have much time to read but I also concur the law of thermodynamics is not being violated, the only point that is valid here is that macronutrient composition can change your metabolism and thus BMR, if I understand their point (which is a bit conflated by the hyperbole)
- handrous 5y ago
  I still wanna know what my body was doing with the extra ~2,000 calories/day I was feeding it from ages 14-22, a period in which I put on only a little height and, by the last half, only gained maybe a pound or two per year. ... also I'd like to know how to get it to start doing that again. (yeah, yeah, I'm sure the answer is "take T and HGH, they're basically magic, aside from all the other health problems they give you")
mayneack 5y ago
Did a double take when I read the authors. https://en.wikipedia.org/wiki/Richard_D._Feinman https://en.wikipedia.org/wiki/Richard_D._Feinman
- joelhoffman 5y ago
  Same here especially given the topic and the sardonic tone. I wonder if the biochemist takes some inspiration from his near-namesake.
nserrino 5y ago
I guess this is like saying "A Joule is a Joule" regarding different types of energy (gravitational potential, nuclear, etc). It may be true in an abstract sense, but the conversion efficiency makes a large impact in a practical sense.
- 6gvONxR4sf7o 5y ago
  In this case, it seems like it only makes a small practical impact.
  - darkarmani 5y ago
    ~300 Calories a day is huge though! It only sounds small if you don't realize what a safe calorie restricted diet deficit should be.
    - 6gvONxR4sf7o 5y ago
      I don't think 300 is anything less than huge. I agree there. But that's for going all the way to a keto diet. In terms of practical impact, I'm thinking of it more in terms of bang for your buck. If you make the kind of change I expect most dieters will make, then you'd only see a small fraction of the 300 delta, which is where I'm coming from.
nyokodo 5y ago
Giles Yeo is a great source of popular information along the lines of this topic. I recommend his books, but here is a recent youtube from his talk at The Royal Institution https://www.youtube.com/watch?v=GQJ0Z0DRumg https://www.youtube.com/watch?v=GQJ0Z0DRumg
wrycoder 5y ago
Here, we propose that a misunderstanding of the second law accounts for the controversy about the role of macronutrient effect on weight loss and we review some aspects of elementary thermodynamics. We use data in the literature to show that thermogenesis is sufficient to predict metabolic advantage. Whereas homeostasis ensures balance under many conditions, as a general principle, "a calorie is a calorie" violates the /second/ law of thermodynamics.
Someone1234 5y ago
The surrounding discussion is an interesting hypothetical. The problem occurs when people use unsettled science like "not all calories are created equal" to change their lifestyle (e.g. "all X diet"), then fail at making substantial change because they made it too complicated. You can do very well believing "a calorie is a calorie" even if it is technically inaccurate, and you can do very badly believing "not all calories are created equal" even if it is technically true on some level. Effective weight loss is simple (note I didn't say "easy"): - Calculate your TDEE. TDEE is ((RMR + TEF + NEAT) * Physical Activity Level). - Eat fewer calories than your TDEE in order to lose body fat or eat more to gain body fat. - Most of the population are Sedentary or Moderately active. Many also overestimate their PAL by one level (i.e. you aren't "Vigorously" because you hit the gym twice this week for 20 minutes, you're Moderately). - Exercise to improve overall health (mental, sleep, immune system, etc). Don't "double count" exercise calories, just set your PAL level and that's it. - Don't eat less than 1500 / 1300 calories for men / women respectively and try to get some nutrients. Ignore everything else, it is just adding complexity. Weight loss should be "Simple but hard." "Complex but easy" doesn't exist unfortunately, at least not in the medium to long term. Instead, you'll just burn out faster. So K.I.S.S., make it boring, make it a habit, eat whatever you want below your TDEE. PS - Starting new exercise (or periods in women) can cause short term water weight increases in the order of 1-6 lbs. This is caused by inflammation. It is completely normal and will go away on its own. Just be patient.
- 6gvONxR4sf7o 5y ago
  That's a whole lot of acronyms. Any links for people who want to learn more or learn how to calculate/measure those things?
  - ryanchants 5y ago
    Stronger By Science has had a recent series of articles on these topics, I would recommend starting there. The last one was just posted today and I haven't dug too deep. From Mass to Energy: The Basic Physiology of Calories https://www.strongerbyscience.com/energy-balance-calories/ https://www.strongerbyscience.com/energy-balance-calories/ Calories and Weight: From the Lab to the Real World https://www.strongerbyscience.com/calories-weight/ https://www.strongerbyscience.com/calories-weight/ The Definitive Diet Setup Guide: How to Build and Adjust a Smart Nutrition Plan https://www.strongerbyscience.com/diet/ https://www.strongerbyscience.com/diet/
015a 5y ago
A cup of gasoline has ~2,000 calories. Assuming you don't die from drinking it, this trivially and obviously would not have the same impact as eating 2 McDonald's McDoubles. But it does have the same calories. So, it turns out, calories are kinda useless if your body can't break down what they're contained in. You'd poop it out, calories intact (or breathe it out, pee it out, or in the case of gasoline, probably just die). Even pulling back into things which are wholly edible: ever heard of the meat sweats? They can occur because your body has to expend a lot of energy in breaking apart proteins commonly found in meats; more-so than while digesting other foods. In other words, if you eat 400 calories of meat, but it takes an investment of 30 calories to digest it, how does that compare to 400 calories of tomatoes? What about lactose intolerance? The inability to digest, and gain nutrients, from milk products. One person drinks 200 calories of milk and gets lots of nutrients; another shits their pants and is now dehydrated. It seems trivially obvious to me that anyone who says "a calorie is a calorie" is trying to sell you something. Though, I suppose, the people who say "my diet will work for you, buy my special food plan" are saying the opposite, but are also trying to sell you something.
- josephcsible 5y ago
  Don't nutrition facts labels already not count calories that you can't absorb (e.g., dietary fiber)?
- bena 5y ago
  You're confusing "inside of me" as "consumed". I can stick my fist in my mouth, but no one would say I've consumed 100 (?) calories of fist. Also, 400 calories of steak is roughly 6oz. 400 calories of tomatoes is about 20 tomatoes. Or about 80oz. It's better to say that every calorie taken in is a calorie that must be accounted for. So if you're lactose intolerant and drink a cup of milk, we can account for that milk when you blow it out of your ass in a bit.
- SkeuomorphicBee 5y ago
  I honestly thought that the quoted "Calories" on food packages were a measure of typical bio-available energy, and not simply a measure of the total theoretical oxidation energy.
bloaf 5y ago
If, as shown in their energy diagram, all food converts to CO2 and H2O, then no foods can cause weight gain because all the carbon will be exhaled and water excreted. I read this as an indication that numbers out of a calorimeter don't correspond precisely to the bio-available energy.
- josephcsible 5y ago
  The conversion to CO2 and H2O happens when you use the energy, not when you digest the food.
bena 5y ago
The problem isn't metabolic or thermodynamic or anything like that. The problem is measurement. We cannot actually measure calories in or out in a direct way. If I eat an apple, I know that X grams of apple will be about Y calories. Usually. For typical apples. I cannot actually measure the apple I ate. It's a destructive process. Both the measuring and the eating. Similarly, I cannot measure the caloric expenditure of everything I expel. Either through breath, sweat, heat, waste, etc. It's difficult. We have approximations. And it's hard to get that information because we're always breathing, drinking, eating, sweating, urinating, defecating, etc. So if were to weigh myself right now, fast for the entire day, then come back in 24 hours and weigh myself again, I'd still only have an approximation of how many calories I expended in that time. When we talk about how things are "processed" what we are really doing is talking about whether or not they are processed. A calorie that gets expelled through waste is not really a calorie consumed. It just passed through you. Look back to Olestra. It was marketed as a sort of 0 calorie oil because it wasn't processed by the body. It would pass right through you. Which kind of was the problem with it. But there are other ways to cause your body to reject calories ingested. It's the mechanism behind bulimia. You can cause yourself to vomit or take laxatives to cause yourself to defecate. Whereas anorexia modifies the CI part of things. End of the day, you find out roughly how many calories you burn a day and then eat roughly that many calories a day, you'll hover in your current weight range. Want to lose weight? Eat less than that. Gain? Eat more than that.
KoftaBob 5y ago
The debate around "A calorie is a calorie" relates to the whole "calories in vs calories out" concept for weight loss/gain. Examples like "500 calories of twinkies and 500 calories of lettuce are equivalent" focus heavily on the "calories in", but forget to consider the "calories out" aspect. What I mean there is, when someone says that the body processes different macronutriets differently, a lot of that has to do with how it affects "calories out" If you eat 500 calories of a food that your body will only process a small amount of, and expel the other 450 calories as waste, that 450 is part of the "calories out". That's only a net "calories in" of 50. On the other hand, if you eat 500 calories of a food that your body chooses to process/store most of, that's 400 calories in, and only 100 calories out. To clarify, I'm not talking as much about absorption, more-so about things like how a macronutrient affects insulin sensitivity. Carbohydrates decrease insulin sensitivity more than protein and unsaturated fats would. Decreased insulin sensitivity means increased insulin resistance. "Having insulin resistance means that the walls of the cells within the body that need to take in glucose for energy, have a much-lowered sensitivity to insulin. This makes it harder for the cells to receive the necessary glucose through the cell wall. That glucose then remains in the bloodstream, resulting in high blood sugar levels, which the liver then has to manage. When this excess sugar reaches the liver, it is converted to fat. The fat cells leave the liver via the bloodstream and cause weight gain. If left unmanaged this can lead to obesity." The calories out part of the equation isn't just the energy you expend per day through movement/metabolic processes/etc, it's also the calories that are expelled as waste because the body didn't store that macronutrient.
leephillips 5y ago
Most of the comments so far are missing the point. The paper points out that the energy available from food, for doing work, creating fat, or any other process, is not, and can not be, equal to the energy content of the food: it is reduced by thermogenesis. Because the reaction pathways are different for different types of food, a calorie of protein does not provide the same usable amount of energy as a calorie of lipid, for example. A greater portion of the protein calorie goes to waste heat. However, from their Figure 2, you can see that the effect of even large changes in dietary composition have a small effect on the energy available from food. You can drastically reduce your carbohydrate consumption, while maintaining your 2000 calorie intake, and that amounts to only about a 100 calorie reduction in available energy. The conclusion: to a reasonable degree of accuracy it really is CICO. To lose weight, eat fewer calories.
- darkarmani 5y ago
  This is similar to lumens vs power. What we care about is a calorie normalized by the ability of the body to get usable energy out of it. Lightbulbs (lumens) are measured in useful (perceived) light created.
mym1990 5y ago
I recently started tracking my daily calorie intake with Noom, and I was very surprised at how easy it is to get to 2000 calories if the diet doesn't consist of low calorie dense foods. I'm now focusing more on eating foods that are have a higher water content and foods that have a good fiber content. If I am still hungry after eating those foods, then I go for something else. I also don't refrain from sweets of simple carbs, but I do try to make mindful decisions about how often to consume them.
punnerud 5y ago
TL;DR: “ the first law holds even in irreversible processes – energy is still conserved – the second law says that something is lost, something is unrecoverable (..) The efficiency of a machine is dependent on how the machine works and, for a biochemical machine, the nature of the fuel and the processes enlisted by the organism. (..) In weight loss diets, of course, inefficiency is desirable and is tied to hormonal levels and enzyme activities. (..) The second law of thermodynamics says that variation of efficiency for different metabolic pathways is to be expected. Thus, ironically the dictum that a "calorie is a calorie" violates the second law of thermodynamics, as a matter of principle.” About the above text: Tried to cut parts from the article to abstract the main points.
armchairhacker 5y ago
Sure, the body loses some energy processing calories (TEF, thermic effect of food). But it's very efficient. The larger flaw behind "CICO" reasoning is that it often ignores volume, hunger, and mood effects. 1200 calories of spinach will make you gain about as much as 1200 calories of sugar. But the former is basically impossible to eat: spinach comes to 23 calories per 100g, so you would have to eat ~5.017kg, or ~11lbs, to eat 1200 calories (sugar is 0.3kg or 0.6lb). When people say things like "500 calories of spinach = 500 calories of chocolate", well technically they're correct, but it's unfair because nobody is eating 500 calories of spinach. And yes, spinach is an extreme example. You can gain weight on healthy "low calorie" foods like chicken and apples. But you'll be stuffed. Most people, when trying to lose weight on processed foods, will constantly battle hunger and low energy. But when they eat unprocessed foods, they have much less hunger and feel better. Even when people say "I'm eating healthy but not losing weight", usually most of the foods they're eating are still high calorie (e.g. cheese and nuts).
dkarl 5y ago
The purpose of "a calorie is a calorie" is not to be scientific truth; it is to serve as guidance for people who are trying to lose weight and are falling prey to particular mistakes. It's like if you're at the gym and a coach is telling someone "sit your butt back, butt back, butt back!" "Sit your butt back" isn't a universal directive for that exercise, much less everything you need to know about it. It's a correction for what that person is currently doing wrong. Six months from now, they might be sitting too far back, and the coach will say, "Don't let your butt go back!" Or the advice to, "Loosen up; people like it when you just say what's on your mind," versus, "You need to activate the filter between your brain and your mouth." These statements can both be true when directed at the right person in the right context. The paper takes aim at "a calorie is a calorie" as an objective scientific truth, which makes it trivially wrong, but doesn't address its pragmatic truth as advice. "A calorie is a calorie" is "true" when it is a good corrective for the person it's directed at. It's "false" if the person needs to be paying more attention to the differences, like if you're an athlete trying to fine-tune your diet for performance, or if you somehow never got the message that people need vegetables in their diet. It might be less true on HN, but in my experience with my family and acquaintances, "a calorie is a calorie" is a widely needed truth. Most people's approach to healthy eating is to sort foods into "good" and "bad" and try to minimize the harm from the "bad" foods, ignoring any potential for harm from the "good" foods. Some people give themselves a pass on the calories from olive oil and avocados because it's a "healthy fat." Other people focus on their intake of cheap processed corporate foods while not worrying about the generous quantities of expensive, local, artisanal bread and cheese and fancy meats they consume. There are even people in my generation who missed the whole last thirty years of carb controversy and mound up huge portions of spaghetti and garlic bread next to a 4oz cut of steak and call that a healthy meal because the only problematic food on the plate is in a tiny portion. For whatever reason, whether it's because of how nutritional information is presented to the public by experts or because of exploitative marketing from the diet industry or because our brains are wired to see good and bad everywhere, that's how an unfortunately very large number of people approach eating for weight loss, and "a calorie is a calorie" is a good corrective for them, to remind them to pay attention to the quantity of everything they eat, not just the "bad" stuff.
kazinator 5y ago
> If a "calorie is a calorie" were true, nobody would pay extra for high test gasoline. The total output of an engine has to come from the stoichiometry of the fuel, regardless of its anti-knock properties. The total output is the work obtained plus heat, plus whatever energy remains in any incomplete combustion products that are exhausted. Inefficiency caused by knocking means we get less work, but that has to be accompanied by more heat. If we are only measuring heat, or only work, we are doing it wrong. One way is to simply reduce one to the other: make the engine do some work against friction which wastes all of it as heat, and put that whole thing in a closed system (the calorimeter). It cannot be that you get more or less heat out of it if you burn the same amount of gasoline, and obtain the same exhaust products. The conservation of energy principle is inviolable. If we capture and measure all of the inputs and outputs of an organism (heat, work and solid/liquid/gaseous matter), then any discrepancy between the energy content of two means it is losing energy from its energy stores, or else accumulating it. The main fallacies in fat control are not violations of thermodynamic principles per se but rather these: (1) it's easy to simultaneously control the work/heat output and/or the input to obtain an arbitrary desired caloric deficit. (2) a caloric deficit will always be covered by releasing and burning fat in preference to anything else.
tpoacher 5y ago
Or more precisely: "The particular interpretation of the adage 'a calorie is a calorie' that we have chosen here violates the second law of thermodynamics."
Protostome 5y ago
the calorie is a very bad metric for human energy consumption and nutrition in general. First, it completely ignores other nutrients like minerals, vitamins, prebiotic fibers, etc. Second, to measure the caloric value of something, you'll need to burn it and calculate the amount of heat generated. This is not how the human body digests food. Many types of substances can't be digested (like fibers) but generate a substantial amount of heat. Bits and pieces of nuts and seeds can go undigested through to a large extent, depends on the size of the pieces that were swallowed, and so the body absorbs only parts of the fats, carbs and proteins in those types of foods (although nuts are very calorie dense) We really need a new measure of energy that's suited for nutrition... The calorie is worthless.

73 points by wrycoder 5y ago

Absolutely hyperbolic title. Sure, "A calorie cannot exceed a calorie" is more correct, but it's less punchy so nobody uses it. The point is that you can't get free energy from nowhere. It's very well illustrated by DNP: https://en.wikipedia.org/wiki/2,4-Dinitrophenol https://en.wikipedia.org/wiki/2,4-Dinitrophenol

cammil 5y ago
That's not what they are saying.
bri3d 5y ago
To many, the point of "a calorie is a calorie" is not that you can't get free energy from nowhere, it's that that diet / food selection is meaningless as food containing one calorie of potential will always evolve to one calorie's worth of metabolic energy through some metabolic process or another - as in the abstract, that two "isocaloric" diets will always produce the same results. The idea of the paper is to dispel this notion.
- gamblor956 5y ago
  The point of the article is that this is not true. Chemically, a calorie is a calorie. But one calorie of fat is metabolically different from the equivalent caloric value of protein, because food is not processed by the body the same way that a calorie is measured.
  - NikolaeVarius 5y ago
    It doesn't matter. If I eat nothing but 500 calories of Twinkies/cake/pure sugar (as measured on the label) every single day, I guarantee I will lose weight. Literally no amount of hand wringing will change that fact
    - CydeWeys 5y ago
      This is a strawman rebuttal. That's not remotely what the person you're replying to said.
    - KoftaBob 5y ago
      The debate around "A calorie is a calorie" relates to the whole "calories in vs calories out" concept for weight loss/gain. Examples like yours focus heavily on the "calories in", but forget to consider the "calories out" aspect. What I mean there is, when someone says that the body processes different macronutriets differently, a lot of that has to do with how it affects "calories out" If you eat 500 calories of a food that your body will only process a small amount of, and expel the other 450 calories as waste, that 450 is part of the "calories out". That's only a net "calories in" of 50. On the other hand, if you eat 500 calories of a food that your body chooses to process/store most of, that's 400 calories in, and only 100 calories out. The calories out part of the equation isn't just the energy you expend per day through movement/metabolic processes/etc, it's also the calories that are expelled as waste because the body didn't store that macronutrient.
      - josephcsible 5y ago
        > If you eat 500 calories of a food that your body will only process a small amount of, and expel the other 450 calories as waste Does this much lack of absorption ever actually happen, though, outside of exceptional cases like if you get food poisoning?
        KoftaBob 5y ago
        I used an exaggerated ratio to drive the point home. To clarify, I'm not talking as much about absorption, more-so about things like how a macronutrient affects insulin sensitivity. Carbohydrates decrease insulin sensitivity more than protein and unsaturated fats would. Decreased insulin sensitivity means increased insulin resistance. "Having insulin resistance means that the walls of the cells within the body that need to take in glucose for energy, have a much-lowered sensitivity to insulin. This makes it harder for the cells to receive the necessary glucose through the cell wall. That glucose then remains in the bloodstream, resulting in high blood sugar levels, which the liver then has to manage. When this excess sugar reaches the liver, it is converted to fat. The fat cells leave the liver via the bloodstream and cause weight gain. If left unmanaged this can lead to obesity."
- dahfizz 5y ago
  This smells like a straw man. From the article: > it is important to understand exactly what it is meant by "a calorie is a calorie." The most common meaning is that is it impossible for two isocaloric diets to lead to different weight loss. I think that is hyperbolic - I've never heard that all isocaloric diets are guaranteed to result in the exact same weightloss. The point of "a calorie is a calorie" is that you need to reduce calories to lose weight. From the chart in the article, going from a 10% carb diet to a 50% carb diet (which is a huge change) only results in a effective caloric difference of ~130. It is _much_ simpler and more effective to just skip a 100 cal snack than it is to cut all carbs out of your diet.
  - treeman79 5y ago
    According to math yes. Reality is carbs increase hunger making dieting harder.
    - 0x0nyandesu 5y ago
      That's just in your head not something that is universally true for everyone. In my experience all large quantities of food increase hunger because you get your body used it. With carbs it's just easier to eat more in a smaller amount of space.
    - yufhgyjj 5y ago
      Keto, the Qanon of diets.
    - Retric 5y ago
      I lost weight on a high carb diet and I have lost weight on a low carb diet. Day 2 they felt different, but by day 200 the body adjusts and you get hungry either way. To simplify the body approximates the food in your diet, but also measures the amount of fat you have. A great many things trick the first, but the second doesn’t care what or when you eat. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6039924/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6039924/
  - jerf 5y ago
    This is a common motte & bailey argument. If you press in on "are all foods really the same?", you get "Oh, no, of course there are differences", but as soon as you're not pressing we end up right back at "you just have to cut your calories because all calories are exactly the same and it doesn't matter where they come from". Ironically, you demonstrate this in your last paragraph. If all calories are the same, yeah, just cut 100 out some other way. But if they have different effects on hormones, satiety, any number of other systems, then it may not be "simpler and more effective" to "just" drop 100 calories as a snack. You may need to actually change what you eat.
- CydeWeys 5y ago
  > it's that that diet / food selection is meaningless as food containing one calorie of potential will always evolve to one calorie's worth of metabolic energy through some metabolic process or another Maybe that's true evolutionarily over tens of millions of years, but it's definitely not true that cellulose calories are remotely equivalent to fat calories -- not unless you're already a ruminant, anyway. Similar issues may present themselves with other types of calories. Just because in theory we could evolve to optimally use all potential sources of energy in food doesn't mean that we actually have yet.
  - Ekaros 5y ago
    Also I believe there is some types of fats that aren't as easily digested. Might be some too that are not at all. Whole system is rather complicated process and don't exactly simplify to equalling same energy you get from burning or is stored in chemical bonds...
- EamonnMR 5y ago
  You would be surprised how many otherwise serious people have advanced to me the notion that you can get more than a calorie from a calorie of food, mostly in service of the notion that weight loss is impossible and you shouldn't try.
wrycoder 5y ago
The article refers to the usage in nutrition science: CICO - "calories in equal calories out". We are learning that this is not the whole truth.
- kleiba 5y ago
  The notion "a calorie is a calorie", however, refers only to the "CI" part.
- na85 5y ago
  The problem is it's very poorly understood, even by medical professionals. I had this very argument with an MD who was trying to tell me that if you operate at a sustained caloric deficit you'll eventually stop losing weight. On some level, CICO must be true. Famine is a thing. If you consume a very small but still nonzero amount of calories you will eventually die. So it's not correct to say that "CICO is BS" or anything similar. Whether CICO is an effective way of sustainable weight loss is another conversation.
  - whatshisface 5y ago
    >I had this very argument with an MD who was trying to tell me that if you operate at a sustained caloric deficit you'll eventually stop losing weight. Depending on the definition of "sustained" (I assume the MD meant sustained absolute calories per day, not sustained calories below metabolism) it could be true, because as your body shrinks it reduces its metabolism partly because there is simply less of it.
    - na85 5y ago
      Well then you'd reach a caloric equilibrium and you'd no longer be at a sustained deficit.
  - amelius 5y ago
    It's like in medieval times when someone had a toothache, the tooth was pulled. Because a tooth that is not there can't cause pain. It's physically sound! But then someone said: yeah sure, except perhaps we can be smarter about it.
joshribakoff 5y ago
I didn’t have much time to read but I also concur the law of thermodynamics is not being violated, the only point that is valid here is that macronutrient composition can change your metabolism and thus BMR, if I understand their point (which is a bit conflated by the hyperbole)
handrous 5y ago
I still wanna know what my body was doing with the extra ~2,000 calories/day I was feeding it from ages 14-22, a period in which I put on only a little height and, by the last half, only gained maybe a pound or two per year. ... also I'd like to know how to get it to start doing that again. (yeah, yeah, I'm sure the answer is "take T and HGH, they're basically magic, aside from all the other health problems they give you")

mayneack 5y ago

Did a double take when I read the authors. https://en.wikipedia.org/wiki/Richard_D._Feinman https://en.wikipedia.org/wiki/Richard_D._Feinman

joelhoffman 5y ago
Same here especially given the topic and the sardonic tone. I wonder if the biochemist takes some inspiration from his near-namesake.

nserrino 5y ago

I guess this is like saying "A Joule is a Joule" regarding different types of energy (gravitational potential, nuclear, etc). It may be true in an abstract sense, but the conversion efficiency makes a large impact in a practical sense.

6gvONxR4sf7o 5y ago
In this case, it seems like it only makes a small practical impact.
- darkarmani 5y ago
  ~300 Calories a day is huge though! It only sounds small if you don't realize what a safe calorie restricted diet deficit should be.
  - 6gvONxR4sf7o 5y ago
    I don't think 300 is anything less than huge. I agree there. But that's for going all the way to a keto diet. In terms of practical impact, I'm thinking of it more in terms of bang for your buck. If you make the kind of change I expect most dieters will make, then you'd only see a small fraction of the 300 delta, which is where I'm coming from.

nyokodo 5y ago

Giles Yeo is a great source of popular information along the lines of this topic. I recommend his books, but here is a recent youtube from his talk at The Royal Institution https://www.youtube.com/watch?v=GQJ0Z0DRumg https://www.youtube.com/watch?v=GQJ0Z0DRumg

wrycoder 5y ago

Here, we propose that a misunderstanding of the second law accounts for the controversy about the role of macronutrient effect on weight loss and we review some aspects of elementary thermodynamics. We use data in the literature to show that thermogenesis is sufficient to predict metabolic advantage. Whereas homeostasis ensures balance under many conditions, as a general principle, "a calorie is a calorie" violates the /second/ law of thermodynamics.

Someone1234 5y ago

The surrounding discussion is an interesting hypothetical. The problem occurs when people use unsettled science like "not all calories are created equal" to change their lifestyle (e.g. "all X diet"), then fail at making substantial change because they made it too complicated. You can do very well believing "a calorie is a calorie" even if it is technically inaccurate, and you can do very badly believing "not all calories are created equal" even if it is technically true on some level. Effective weight loss is simple (note I didn't say "easy"): - Calculate your TDEE. TDEE is ((RMR + TEF + NEAT) * Physical Activity Level). - Eat fewer calories than your TDEE in order to lose body fat or eat more to gain body fat. - Most of the population are Sedentary or Moderately active. Many also overestimate their PAL by one level (i.e. you aren't "Vigorously" because you hit the gym twice this week for 20 minutes, you're Moderately). - Exercise to improve overall health (mental, sleep, immune system, etc). Don't "double count" exercise calories, just set your PAL level and that's it. - Don't eat less than 1500 / 1300 calories for men / women respectively and try to get some nutrients. Ignore everything else, it is just adding complexity. Weight loss should be "Simple but hard." "Complex but easy" doesn't exist unfortunately, at least not in the medium to long term. Instead, you'll just burn out faster. So K.I.S.S., make it boring, make it a habit, eat whatever you want below your TDEE. PS - Starting new exercise (or periods in women) can cause short term water weight increases in the order of 1-6 lbs. This is caused by inflammation. It is completely normal and will go away on its own. Just be patient.

6gvONxR4sf7o 5y ago
That's a whole lot of acronyms. Any links for people who want to learn more or learn how to calculate/measure those things?
- ryanchants 5y ago
  Stronger By Science has had a recent series of articles on these topics, I would recommend starting there. The last one was just posted today and I haven't dug too deep. From Mass to Energy: The Basic Physiology of Calories https://www.strongerbyscience.com/energy-balance-calories/ https://www.strongerbyscience.com/energy-balance-calories/ Calories and Weight: From the Lab to the Real World https://www.strongerbyscience.com/calories-weight/ https://www.strongerbyscience.com/calories-weight/ The Definitive Diet Setup Guide: How to Build and Adjust a Smart Nutrition Plan https://www.strongerbyscience.com/diet/ https://www.strongerbyscience.com/diet/

015a 5y ago

A cup of gasoline has ~2,000 calories. Assuming you don't die from drinking it, this trivially and obviously would not have the same impact as eating 2 McDonald's McDoubles. But it does have the same calories. So, it turns out, calories are kinda useless if your body can't break down what they're contained in. You'd poop it out, calories intact (or breathe it out, pee it out, or in the case of gasoline, probably just die). Even pulling back into things which are wholly edible: ever heard of the meat sweats? They can occur because your body has to expend a lot of energy in breaking apart proteins commonly found in meats; more-so than while digesting other foods. In other words, if you eat 400 calories of meat, but it takes an investment of 30 calories to digest it, how does that compare to 400 calories of tomatoes? What about lactose intolerance? The inability to digest, and gain nutrients, from milk products. One person drinks 200 calories of milk and gets lots of nutrients; another shits their pants and is now dehydrated. It seems trivially obvious to me that anyone who says "a calorie is a calorie" is trying to sell you something. Though, I suppose, the people who say "my diet will work for you, buy my special food plan" are saying the opposite, but are also trying to sell you something.

josephcsible 5y ago
Don't nutrition facts labels already not count calories that you can't absorb (e.g., dietary fiber)?
bena 5y ago
You're confusing "inside of me" as "consumed". I can stick my fist in my mouth, but no one would say I've consumed 100 (?) calories of fist. Also, 400 calories of steak is roughly 6oz. 400 calories of tomatoes is about 20 tomatoes. Or about 80oz. It's better to say that every calorie taken in is a calorie that must be accounted for. So if you're lactose intolerant and drink a cup of milk, we can account for that milk when you blow it out of your ass in a bit.
SkeuomorphicBee 5y ago
I honestly thought that the quoted "Calories" on food packages were a measure of typical bio-available energy, and not simply a measure of the total theoretical oxidation energy.

bloaf 5y ago

If, as shown in their energy diagram, all food converts to CO2 and H2O, then no foods can cause weight gain because all the carbon will be exhaled and water excreted. I read this as an indication that numbers out of a calorimeter don't correspond precisely to the bio-available energy.

josephcsible 5y ago
The conversion to CO2 and H2O happens when you use the energy, not when you digest the food.

bena 5y ago

The problem isn't metabolic or thermodynamic or anything like that. The problem is measurement. We cannot actually measure calories in or out in a direct way. If I eat an apple, I know that X grams of apple will be about Y calories. Usually. For typical apples. I cannot actually measure the apple I ate. It's a destructive process. Both the measuring and the eating. Similarly, I cannot measure the caloric expenditure of everything I expel. Either through breath, sweat, heat, waste, etc. It's difficult. We have approximations. And it's hard to get that information because we're always breathing, drinking, eating, sweating, urinating, defecating, etc. So if were to weigh myself right now, fast for the entire day, then come back in 24 hours and weigh myself again, I'd still only have an approximation of how many calories I expended in that time. When we talk about how things are "processed" what we are really doing is talking about whether or not they are processed. A calorie that gets expelled through waste is not really a calorie consumed. It just passed through you. Look back to Olestra. It was marketed as a sort of 0 calorie oil because it wasn't processed by the body. It would pass right through you. Which kind of was the problem with it. But there are other ways to cause your body to reject calories ingested. It's the mechanism behind bulimia. You can cause yourself to vomit or take laxatives to cause yourself to defecate. Whereas anorexia modifies the CI part of things. End of the day, you find out roughly how many calories you burn a day and then eat roughly that many calories a day, you'll hover in your current weight range. Want to lose weight? Eat less than that. Gain? Eat more than that.

KoftaBob 5y ago

The debate around "A calorie is a calorie" relates to the whole "calories in vs calories out" concept for weight loss/gain. Examples like "500 calories of twinkies and 500 calories of lettuce are equivalent" focus heavily on the "calories in", but forget to consider the "calories out" aspect. What I mean there is, when someone says that the body processes different macronutriets differently, a lot of that has to do with how it affects "calories out" If you eat 500 calories of a food that your body will only process a small amount of, and expel the other 450 calories as waste, that 450 is part of the "calories out". That's only a net "calories in" of 50. On the other hand, if you eat 500 calories of a food that your body chooses to process/store most of, that's 400 calories in, and only 100 calories out. To clarify, I'm not talking as much about absorption, more-so about things like how a macronutrient affects insulin sensitivity. Carbohydrates decrease insulin sensitivity more than protein and unsaturated fats would. Decreased insulin sensitivity means increased insulin resistance. "Having insulin resistance means that the walls of the cells within the body that need to take in glucose for energy, have a much-lowered sensitivity to insulin. This makes it harder for the cells to receive the necessary glucose through the cell wall. That glucose then remains in the bloodstream, resulting in high blood sugar levels, which the liver then has to manage. When this excess sugar reaches the liver, it is converted to fat. The fat cells leave the liver via the bloodstream and cause weight gain. If left unmanaged this can lead to obesity." The calories out part of the equation isn't just the energy you expend per day through movement/metabolic processes/etc, it's also the calories that are expelled as waste because the body didn't store that macronutrient.

leephillips 5y ago

Most of the comments so far are missing the point. The paper points out that the energy available from food, for doing work, creating fat, or any other process, is not, and can not be, equal to the energy content of the food: it is reduced by thermogenesis. Because the reaction pathways are different for different types of food, a calorie of protein does not provide the same usable amount of energy as a calorie of lipid, for example. A greater portion of the protein calorie goes to waste heat. However, from their Figure 2, you can see that the effect of even large changes in dietary composition have a small effect on the energy available from food. You can drastically reduce your carbohydrate consumption, while maintaining your 2000 calorie intake, and that amounts to only about a 100 calorie reduction in available energy. The conclusion: to a reasonable degree of accuracy it really is CICO. To lose weight, eat fewer calories.

darkarmani 5y ago
This is similar to lumens vs power. What we care about is a calorie normalized by the ability of the body to get usable energy out of it. Lightbulbs (lumens) are measured in useful (perceived) light created.

mym1990 5y ago

I recently started tracking my daily calorie intake with Noom, and I was very surprised at how easy it is to get to 2000 calories if the diet doesn't consist of low calorie dense foods. I'm now focusing more on eating foods that are have a higher water content and foods that have a good fiber content. If I am still hungry after eating those foods, then I go for something else. I also don't refrain from sweets of simple carbs, but I do try to make mindful decisions about how often to consume them.

punnerud 5y ago

TL;DR: “ the first law holds even in irreversible processes – energy is still conserved – the second law says that something is lost, something is unrecoverable (..) The efficiency of a machine is dependent on how the machine works and, for a biochemical machine, the nature of the fuel and the processes enlisted by the organism. (..) In weight loss diets, of course, inefficiency is desirable and is tied to hormonal levels and enzyme activities. (..) The second law of thermodynamics says that variation of efficiency for different metabolic pathways is to be expected. Thus, ironically the dictum that a "calorie is a calorie" violates the second law of thermodynamics, as a matter of principle.” About the above text: Tried to cut parts from the article to abstract the main points.

armchairhacker 5y ago

Sure, the body loses some energy processing calories (TEF, thermic effect of food). But it's very efficient. The larger flaw behind "CICO" reasoning is that it often ignores volume, hunger, and mood effects. 1200 calories of spinach will make you gain about as much as 1200 calories of sugar. But the former is basically impossible to eat: spinach comes to 23 calories per 100g, so you would have to eat ~5.017kg, or ~11lbs, to eat 1200 calories (sugar is 0.3kg or 0.6lb). When people say things like "500 calories of spinach = 500 calories of chocolate", well technically they're correct, but it's unfair because nobody is eating 500 calories of spinach. And yes, spinach is an extreme example. You can gain weight on healthy "low calorie" foods like chicken and apples. But you'll be stuffed. Most people, when trying to lose weight on processed foods, will constantly battle hunger and low energy. But when they eat unprocessed foods, they have much less hunger and feel better. Even when people say "I'm eating healthy but not losing weight", usually most of the foods they're eating are still high calorie (e.g. cheese and nuts).

dkarl 5y ago

The purpose of "a calorie is a calorie" is not to be scientific truth; it is to serve as guidance for people who are trying to lose weight and are falling prey to particular mistakes. It's like if you're at the gym and a coach is telling someone "sit your butt back, butt back, butt back!" "Sit your butt back" isn't a universal directive for that exercise, much less everything you need to know about it. It's a correction for what that person is currently doing wrong. Six months from now, they might be sitting too far back, and the coach will say, "Don't let your butt go back!" Or the advice to, "Loosen up; people like it when you just say what's on your mind," versus, "You need to activate the filter between your brain and your mouth." These statements can both be true when directed at the right person in the right context. The paper takes aim at "a calorie is a calorie" as an objective scientific truth, which makes it trivially wrong, but doesn't address its pragmatic truth as advice. "A calorie is a calorie" is "true" when it is a good corrective for the person it's directed at. It's "false" if the person needs to be paying more attention to the differences, like if you're an athlete trying to fine-tune your diet for performance, or if you somehow never got the message that people need vegetables in their diet. It might be less true on HN, but in my experience with my family and acquaintances, "a calorie is a calorie" is a widely needed truth. Most people's approach to healthy eating is to sort foods into "good" and "bad" and try to minimize the harm from the "bad" foods, ignoring any potential for harm from the "good" foods. Some people give themselves a pass on the calories from olive oil and avocados because it's a "healthy fat." Other people focus on their intake of cheap processed corporate foods while not worrying about the generous quantities of expensive, local, artisanal bread and cheese and fancy meats they consume. There are even people in my generation who missed the whole last thirty years of carb controversy and mound up huge portions of spaghetti and garlic bread next to a 4oz cut of steak and call that a healthy meal because the only problematic food on the plate is in a tiny portion. For whatever reason, whether it's because of how nutritional information is presented to the public by experts or because of exploitative marketing from the diet industry or because our brains are wired to see good and bad everywhere, that's how an unfortunately very large number of people approach eating for weight loss, and "a calorie is a calorie" is a good corrective for them, to remind them to pay attention to the quantity of everything they eat, not just the "bad" stuff.

kazinator 5y ago

> If a "calorie is a calorie" were true, nobody would pay extra for high test gasoline. The total output of an engine has to come from the stoichiometry of the fuel, regardless of its anti-knock properties. The total output is the work obtained plus heat, plus whatever energy remains in any incomplete combustion products that are exhausted. Inefficiency caused by knocking means we get less work, but that has to be accompanied by more heat. If we are only measuring heat, or only work, we are doing it wrong. One way is to simply reduce one to the other: make the engine do some work against friction which wastes all of it as heat, and put that whole thing in a closed system (the calorimeter). It cannot be that you get more or less heat out of it if you burn the same amount of gasoline, and obtain the same exhaust products. The conservation of energy principle is inviolable. If we capture and measure all of the inputs and outputs of an organism (heat, work and solid/liquid/gaseous matter), then any discrepancy between the energy content of two means it is losing energy from its energy stores, or else accumulating it. The main fallacies in fat control are not violations of thermodynamic principles per se but rather these: (1) it's easy to simultaneously control the work/heat output and/or the input to obtain an arbitrary desired caloric deficit. (2) a caloric deficit will always be covered by releasing and burning fat in preference to anything else.

tpoacher 5y ago

Or more precisely: "The particular interpretation of the adage 'a calorie is a calorie' that we have chosen here violates the second law of thermodynamics."

Protostome 5y ago

the calorie is a very bad metric for human energy consumption and nutrition in general. First, it completely ignores other nutrients like minerals, vitamins, prebiotic fibers, etc. Second, to measure the caloric value of something, you'll need to burn it and calculate the amount of heat generated. This is not how the human body digests food. Many types of substances can't be digested (like fibers) but generate a substantial amount of heat. Bits and pieces of nuts and seeds can go undigested through to a large extent, depends on the size of the pieces that were swallowed, and so the body absorbs only parts of the fats, carbs and proteins in those types of foods (although nuts are very calorie dense) We really need a new measure of energy that's suited for nutrition... The calorie is worthless.