Weight management: that good old medical chestnut, CI-CO

The Calories In-Calories Out (CI-CO) Fallacy

CI-CO is the argument heard most when people say, "I eat well and workout a lot yet can't shift weight": people suspect I am a liar because science behind the law of thermodynamics is simple, complete and irrefutable. There is not a “Law of Thermodynamics” but four. Since people aren’t concerning themselves with the entropy of a crystal at absolute zero, let us assume they are referring to the first law. It can be reasonably assumed that they are parroting something they heard from someone else; possibly medical school, where they are also told that 50% of what they hear will either change or is simply ‘untrue’.

The first law states that in a thermodynamic process the increment in the internal energy of a system is equal to the increment of heat supplied to the system, minus the increment of work done by the system on its surroundings. It is often simplified to “energy can neither be created nor destroyed only transformed or transferred”. I do not disagree with that law but note: “In a thermodynamic process…”; this is a gross misrepresentation of the human body as a perfect thermodynamic process.

Consider four issues:

Issue 1: The assumption that there is no option for calories other than to be burned or stored

Carbohydrates basically work that way. Fats and proteins have other jobs to perform on the body. Protein does everything from building muscle cells to repairing cell membranes. Fat transports non-water-soluble nutrients, insulates neurons, and can be used to repair cell membranes. Fat and protein can be broken down and recombined into whatever the body needs. Eat a steak and your body might use it to make a cell membrane; Alfredo sauce might be used to produce insulate neurons in the brain. Fat and protein are to the body what wood is to us; burn it for fuel, build a house with it or turn it into paper. In any event, calories in the proteins and fats used in this manner are neither burned nor stored. The first hole in CI-CO.

Issue 2: The assertion that Basal Metabolic Rate (BMR) is Easily Predictable and Stable

Your BMR is the number of calories you would need to stay alive for 24 hours if you spent the day still and in bed; it is what would be required for breathing, heart rate, etc. It is typically calculated using the Harris-Benedict equation. James Harris was a botanist who freely admitted that his equation failed to take into account large amounts of muscle mass or the additional calories provided by excess body fat and that it was thus much more effective for individuals at, or very close to, ideal body weight. It is well documented that BMR responds to decreased caloric intake by slowing down. So if two friends have the exact same Harris-Benedict score, but one has been dieting, then the dieter will actually burn less calories at rest than his friend. Said another way, if these two friends eat the same number of calories in excess of their BMR score, the dieter will gain more weight than the non-dieter. Again, in this case CI-CO can’t hold up.

Issue 3: The requirement that the body be a perfectly efficient calorie burning machine

The Second Law of Thermodynamics explains entropy which only applies in a closed system: the human body is not closed. [The first law also applies to a closed system and, as such, people who think the first law applies to the human body would have a difficult time weaseling out of saying the second law applies.] The Second Law dates back to the mid-1800’s and explains the efficiencies of a closed system: it basically says it is impossible to create a system that has perfect efficiency of energy conversion, as there are always some losses in the conversion process. The maximum possible efficiency is different than the observed efficiency. Over time, entropy increases and a system becomes more disordered and less efficient. Early in the developing science of thermodynamics, researchers realized that while work could be converted completely into heat, the converse is never true for a cyclic process. “Certain natural processes were also observed always to proceed in a certain direction” (e.g. heat always moves from hot to cold). A machine that converts heat from a warm body into work, without losing heat to a cooler body, would violate the second law of thermodynamics. The Second Law is why physicists know that a perpetual motion machine is impossible (and not so simple, either). CI-CO cannot explain human metabolism or much else human.

The human body is even more complicated because ability to burn/store/use nutrients is affected by genetics, environment, hormones, previous caloric restriction and subsequent reduction in BMR, hydration level, chemicals etc. Calories eaten and calories used in voluntary movement are only two small parts of energy balance and, unless all other countless, wildly varying variables (internal and external) are controlled they are meaningless by themselves. As with metabolism, such variables never can be controlled as they are involved in affecting the efficiencies of a system over which we have no control.

Issue 4: For long term weight loss using this theory, then we’d have to eventually turn to starvation

If we wanted to use CI-CO effectively, knowing what we now know about entropy and how decrease in caloric intake causes decreased basal metabolic rate, we would just have to keep decreasing our calories and increasing our exercise until eventually we would be following disordered eating patterns. It would be the only way to stay under our ever plummeting BMR and eat less than we burn. Perhaps this is why 95% of intentional weight loss efforts fail. The body releases weight at first but then the damn science catches up to us and no matter how hard the people who’ve attended a physics amateur hour try to yell to the contrary, they will never be able to out-science the actual laws of thermodynamics and the complicated human body (which is not a lawnmower).

"Thermodynamics tells us nothing about why people do anything".

Bonus: Then there is the friend who eats everything in sight, does no exercise and never gains weight

Everyone knows somebody like this. I have a number of friends who eat way more than I do, exercise less and stay stick thin. Why do these people get to credit their metabolism but I’m just a fat, lazy, excuse-making slob if I suggest that my metabolism may be as slow as theirs is fast? So next time somebody tells you that it’s just CI-CO, consider telling them that you’ll be happy to talk to them about it once they have recited the laws of thermodynamics, defined the Harris-Benedict Equation, then discussed its specific limitations and explained to you how your friend who eats a ton and simply doesn’t gain weight.

Balance in an open system, like the human body, is when all energy going into the system equals all energy leaving the system plus the storage of energy within the system. But energy in any thermodynamic system includes kinetic energy, potential energy, internal energy, and flow energy, as well as heat and work processes. In other words, in real life, balancing energy includes a lot more than just the calories we eat and the calories we burn according to exercise charts. The energy parts of the equation include: calories consumed; calories converted to energy and used in involuntary movement; calories used for heat generation and in response to external environmental exposures and temperatures; calories used with inflammatory and infectious processes; calories used in growth, tissue restoration and numerous metabolic processes; calories used in voluntary movement; calories not absorbed in the digestive tract and matter expelled; calories stored as fat, and fat converted in the liver to glucose; and more. Add to that, to put it simply, each variable affects the others, varies with mass and age, involves complex hormonal and enzyme regulatory influences, and differs in efficiency. CI-CO applied to human metabolism tells neither doctors, nor us, anything about weight management.

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16 Replies

  • As a physicist, it really annoys me when people quote the calories in vs calories out fallacy and refer to it as being 'basic science' or 'simple physics'. There are far too many processes occurring in the human body for it to be simple in any way and if they are going to quote science at us, what about homeostasis? The human body is actually pretty good at compensating for external changes... when it's working properly, that is. Even when it isn't working properly it can compensate for a reduction in calories by reducing TSH and t3 levels and hence metabolism which doesn't help at all with weight loss :(

    Obviously eating too much isn't going to help but it seems that genetics play an important role in obesity alongside chronic inflammation which in itself can be caused by obesity. Maybe those that spout the calories in vs calories out belief should read a little more about their 'basic science' and 'simple physics'. I wonder if they realise that most of the weight of what they eat is breathed back into the atmosphere as carbon dioxide ;)

  • Thank you Pink Ninja, most interesting! And that is exactly what I tell them [doctors]... they try to use the 'basic science' line and I remind them that I understand and it is NOT as they describe!

    'They' should indeed read a little more on the basics before spouting to those, already having a hard time of it, only to be faced with their attempts to lay 'blame' with patients when 'they' don't know enough!

    Yes, I am aware of the affect of reduction in T3 levels... still, in the face of no sensible information from any doc, anywhere [it would seem], many of us are left with trying to 'fix ourselves'.

    One doctor in 2012 even suggested I put on lots more weight [he meant lots!] to qualify for a gastric band. I told him that gastric banding is 'mental', unless in seriously huge diabetic patients. I now retract even that comment. Aside from CI-CO and 'just take one thing out of your diet' [when it had been changed beyond recognition for 5 years + exercise], THAT is the advice I got when unable to lose weight [a bizarre 'adult onset' family issue]... fortunately, I have found something that is finally working, without resorting to NHS ludicrous notions on even WHAT to eat.

    Thank you again, I'll feel a little more buoyed next time I 'shout them down' ;-)

  • Throw in:

    Using pre-calculated calorific values which may differ markedly from those which would apply to the actual food in front of you.

    Variations in the ability of the gut (person to person, day to day, etc.) to digest and absorb foods.

  • Absolutely regarding the gut... that also became a problem, to fix oneself :-)

  • Thank you for that, LindaC.

    My dog's vet quoted the first law of thermodynamics at me not long ago - and, frankly, I wanted to hit him! Yes, my dog is over-weight, but he virtually called me a liar when I said I didn't over-feed him, and said dog isn't really interested in food at all! I tried to argue with him about the 'first law' guff, but he shouted me down - needless to say, i won't be going there again! - and I am still fuming about it!

    In fact, he was so adament about it that I was beginning to doubt my own sanity! So, thank you for reminding me that I'm right and he is wrong!!!

    Bless you for that. :) x

  • And I hope you Don't mind if I copy that and send it to my brother, because we have this arguement quite regularly!

    You are my hero! :D

  • My goodness of course not - anyone, modify it and take it to your docs ;-) Look at what Pink Ninja above has to say too.

  • No, thank you, it's not 'my' docs that are the problem. I Don't have any docs anymore. Besides, I've lost all the weight since I started self-treating.

    But, we often get people on here that go on about CI-CO, and I do try to explain, but now I won't have to! I shall just link them to you! lol :p

  • Hey greygoose, I spent from 2003 until end June 2015 being told its CI-CO: I've always argued the toss with them... because I exercised 200+ mins per week and had an exemplary diet. Don't put up with it ;-) xox

  • Well, I Don't, normally. Not with my own doctors. But this man was twice my weight, and twice as aggressive as me! He was a bully and so self-assured - and he could shout louder than me! Besides, I couldn't explain it as well as you just have.

    He told me that 'obesity is a disease, and the cure is eating less calories'!!! Well, I was so knocked out by the illogicality of that, that I couldn't think quick enough. I mentioned thyroid, and he laughed at me, and said i was just making excuses - and then said, look at me! Well, I was looking!!! He said maybe I should get tested for thyroid! in a very sarcastic tone. I said, dryly, yes, I think you should! I Don't like the look of your eyebrows! He didn't know what to say to that!

    Yes, I know, I should just get over it. lol But, dragging things up all the time is also a hypo symptom.!

  • That is foul and funny simultaneously. Yes, we can all get over stuff, but citing examples can be helpful for others to hear what goes on and how these things can be dealt with. Hey, I know many with no hypothyroid symptoms who 'drag things up' ;-)

  • lol Very true!

  • Way to go! Thank you. Always known there was a flaw but did not have the background to spell it out. I'll save this (but probably forget I've done so. Hey Ho.)

  • Yes crabapple, I knew too - I was living it, doing everything yet with no results - so last time I was told this, I came home and looked it up ;-) Life can sometimes be tough enough without this [criticism and blame] thrown our way too! Hey Ho indeed xx

  • I missed this post up from you, but luckily grey goose pointed me in the right direction.

    Have you got a link to anything official on this subject I can print off please. ?

  • No Coastwalker sorry, I got this info from something cobbled together from an article online... it has been altered and changed over time in any event.

    The first response above to my post is from PinkNinja, a physicist, who clearly shares this view. Since this one is fairly straightforward, I am bound to add that CI-CO is bunkum (as is, you can't be hypothyroid if you don't 'satisfy' our ranges!), quite unlike the many philosophical disputes inevitable within science; those which can't be readily dismissed.

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