5

votes

How do we know thermodynamics applies?

Answered on September 12, 2014
Created August 12, 2011 at 7:36 PM

It is often asserted that caloric imbalance must be at the heart of the weight gain/loss equation because of the first law of thermodynamics "Energy is conserved; it can be neither created nor destroyed.".

But humans are not simple machines. Nutritional intake can be consumed in body tissue repair or growth or simply excreted.

Is there any substantial backup to the assertion?

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 08, 2012
at 02:22 AM

Why do you keep repeating such a trivial thing? You haven't worked out HOW to do it. Lets look at the wikis (not authoritative, but hopefully neutral): http://en.wikipedia.org/wiki/First_law_of_thermodynamics (note reference to closed system). Now look here: http://en.wikipedia.org/wiki/Thermodynamic_system#Open_system By their definition, food in/out is open system. First law FORMULAs do not work on an open system. You don't have a first-law based formula to account for everything going on. No one does. To say "it's possible" is not an answer.

Cccb899526fb5908f64176e0a74ed2d9

(2801)

on March 07, 2012
at 11:22 PM

Or very oily poop, according to the suggested source of those 5000 calories...oof

Cccb899526fb5908f64176e0a74ed2d9

(2801)

on March 07, 2012
at 11:20 PM

Travis, have you ever been overweight? Those of us who managed to eat enough food to get to that state generally have a vastly higher satiety threshold than a naturally lean individual. This, I think, is where genetics may come into play; sure, you can starve anyone down to a certain weight, but even eating nothing but whole foods will leave an ex-obese 130 lb male (cough myself c. 2011) ravenous.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 08:12 PM

And you don't know the basics. No wonder you people never get anything built! http://en.wikipedia.org/wiki/Thermodynamic_system#Open_system

510bdda8988ed0d4b0ec0b738b4edb73

(20898)

on March 07, 2012
at 07:49 PM

"You can't account for biological changes due to the food chemistry itself changing the system." Yes you can! That's what 90% of chemistry is, accounting for the energy changes during chemical reacions (and biology is nothing but chemical reactions). My entire thesis was watching where energy goes during complicated chemical reactions.

510bdda8988ed0d4b0ec0b738b4edb73

(20898)

on March 07, 2012
at 07:48 PM

Dude, you are so wrong it's not even funny. I don't know why I'm arguing with you. Yes, some energy is going to change the state of the system, that's fine. But all of those changes are chemical reactions of some kind that will either take or store (chemical energy). I repeat (for the last time): the TOTAL energy of ANY system (including the human body) is the SUM of the energy the went into it minus the energy the went out of it. Internal changes can take or release energy, but it has to come from/go somewhere. Just because the equations are complicated, doesn't mean they're not true.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 07:21 PM

I think the problem is you guys are really just arguing that there is no such thing as a open system. If the law holds, delta E = 0 anyway. So what? The engineer's use of open system means that when you get out your pencil to actually do the thermo, can you identify your system in such a way that energy in and out can be accounted for? You are saying "its possible." I'm saying "Duh, but you can't do it! It's open."You can't account for biological changes due to the food chemistry itself changing the system."

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 07:13 PM

miked-You don't seem to understand something. We all know "conservation of energy" holds. But, when writing and equation to actually do something with it, you need to identify a closed system or pick another approach. What your Phd didnt tell you is that some of that energy in the human system is going into changing the system itself. It/s not steady state. You can't write a formula for that. That's why the second law doesn't hold. You don't have access to everything you need to completely describe the system. Even phds can learn from lowly mechanical engineers sometimes.

510bdda8988ed0d4b0ec0b738b4edb73

(20898)

on March 07, 2012
at 06:20 PM

Whoa! I missed this whole fight going on in my thread. Exciting! DFH - you're totally wrong here. Any system, open or closed, contains the sum of the heat (energy) that went into in minus the heat (energy) that went out of it (Accounting for what goes in and what goes out is non-trivial). In a closed system, deltaE is 0, so its not even worth talking about. You may have spent two whole semesters on this, but I'm a Ph.D. in Chemical Physics and have had YEARS of statistical thermodynamics. Don't get in over your head.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 06:16 PM

We discovered that its great fun working on rockets until the money runs out!

Medium avatar

(10611)

on March 07, 2012
at 06:11 PM

I see that your link goes to a set of dietary recommendations. I'm not following those rabbit trails to see where they lead. But please tell us what NASA discovered besides Tang.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 06:04 PM

"turn thermodynamics on its head?" I worked at NASA too, and we didn't do that! :)

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 06:03 PM

You misunderstand. You are promoting a calculation no human has ever made as a defense for using the wrong formula. Occam's razor. Any luck finding an example of what you keep proposing? You can't.

Medium avatar

(10611)

on March 07, 2012
at 06:02 PM

You forgot about exercise Max. That's the most Paleo way to increase calories-out. Grok had to be out hunting-and-gathering to survive, metabolizing 70 kcal over and above his RMR for every mile he covered.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 04:57 PM

What? I proposed no such thing. What you keep saying only applies in theory. Show me the math. You can't. It does not exist. Sit down and try writing the equations if you can't understand it any other way. What formula will you use for hormone conversion? Haha

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 04:26 PM

It's becoming more and more obvious that you're unwilling to account for all the inputs and outputs in the system. It's not a simple system that we can be sure of. Propping up an oversimplified strawman does not however invalidate the basic idea behind CICO.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 04:23 PM

Mark-How about you find one example of the first law correctly applied with food consumption in scientific literature, per your simple thought experiment. That should be easy if you are right. You won't find one though. I know people have tried because I saw them. None of them can even get close to modeling process enablers that change the system internally, because all of them are not even understood, some not discovered yet!

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 04:05 PM

That's not the definition of a closed system. But let's talk about the energy conversion. A gets converted to B. There's going to be a loss in energy between B and A. In the exothermic reaction, heat is lost to the surroundings. In the endothermic reaction, heat is input into the system. And then there's the reaction byproducts produced, you have to account for the energy in those as well. And here you go, you can balance the equation.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 04:05 PM

Yes, and no. The problem with your answer is it doesn't matter. Since this in in the context of the incorrect application of the first law, where I shot down your lack of understanding already, it does no one a bit of good to salvage it. The reason we do not use the first law for problems like this is because of problems like this, but you are only trying to salvage it. Sophomoric.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 04:01 PM

I actually had some training in chemical engineering. Inputs, ouputs, heat transfer, boring, boring math, but very applicable to what we're talking about. What you're currently proposing is a one input, one output system. Of course, that fails, because there's multiple outputs, the input itself affects the output, etc...

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 03:56 PM

No, you don't. I don't believe you. You are in over your head.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 03:28 PM

I'm a chemist, I can do the math, I understand the system.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 02:45 PM

Matt- see above answer regarding process enablers inside the body. They change the system. It doesn't work. Let it go.

Medium avatar

(10611)

on March 07, 2012
at 02:42 PM

In my field the people with the government funded similarly non-useful results. The empirical expressions developed at the same time are embedded into all performance predictive models used commercially. The friction between the two groups was useful for discussion but the theoretical approach is now completely forgotten.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 02:34 PM

I think we are on exactly the same page. Health folks used the first law wrong and ran with it.

Medium avatar

(10611)

on March 07, 2012
at 02:17 PM

Again DFH wrong argument. Sophomore physics are inappropriate to explain very well documented physiology. In the field I work in, fundamental physics principles were used to explain the structural mechanics of boxes. This approach failed miserably,but was solved simply and fairly accurately using population statistics in empirical correlations using the known important factors. The same applies to applying thermodynamics theory to solve a problem already well explained with statistics. Wrong tools produce only crude approximations.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 02:00 PM

Some of the energy going in stored as chemical energy gets converted the body, and to changes how the body works. The reactions inside your body that change how food is processed are process enablers. Process enablers change the machine you wish to study. (Example, doing low carb to increase fat burn is a process enabler) For this reason, its not a closed system. All the tech articles that use the first law that I can find do not take this fact I to account. Everyone seems to be making the same mistakes.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 01:54 PM

Matt, again. Don't get in over your head. There is a difference between your thought experiment and actually sitting down to do the math on a human as a system. I know the side you are taking and it's just a thought experiment. Do the math.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 01:52 PM

Matt- that isnt being done. Your answer could work in theory, but again, the problem you run into is why we have a second law. Don't get in over your head.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 01:50 PM

Yes, I'm an engineer, and what I said was not nonsense. Engineers actually take "laws" and do the math!

24df4e0d0e7ce98963d4641fae1a60e5

on March 07, 2012
at 01:48 PM

Nonsense. You're an engineer right DFH? You should know better

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:35 PM

You're proposing an open system that doesn't fit a closed system equation. Of course, it fails.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:27 PM

I agree that the way you eat affects the "calories out" part of the equation. But it's quite likely that Poisson is producing very nutritious poop, meaning they're simply not absorbing all those 5000-10000 kcal.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 01:25 PM

To make this a bit more clear-There is a big difference when you are using a physical law for a thought experiment (hey this makes sense) and when you sit down and start doing the math. This is when you need to define and understand your boundary conditions and define the system your equation is working. To say the entire universe meets the first law is trivial. No equation. Duh. Now write one for a human, and show the chemical storage inside in/out/converted in the math. No one is doing this that I can find. I saw a few attempts at it though. Again, this is what the second law is for.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:23 PM

Only Travis would bring satiety to a thermodynamics party. :P

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:22 PM

If you ignore certain outputs (heat, waste, etc...) you will necessarily violate the first law, because you're making it into an open system. Account for everything and the body is a closed system, first law rules it.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:19 PM

CICO only "fails" when folks oversimplify it. If you start taking into account the actual energy extraction from food (i.e. your poop still has chemical energy) and differences in biochemical energy yield from different sources (thermic effect of macronutrients), CICO works.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 01:19 PM

Dude, I spent two semesters with this stuff! It only applies to a closed system. My coop is right. I know what you are getting at though. If you did have a way to fully account for all the chemical processes going on inside, you may eventually come up with a very complex model that can work. This is part of the reason why we have the second law. People just abused the first law and it went too far. The equations people are using from it are wrong. True story.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:16 PM

It is correct that different nutrients have different biochemical energy yields. Thus a calorie is not necessarily a calorie in a biochemical system, but that little to do with the second law. It's more of a problem ignoring some forms of energy and incomplete equations.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:08 PM

DHF, you're mistaken. If you account for all inputs and outputs, energy balance must be achieved. That is the first law.

Medium avatar

(10611)

on March 07, 2012
at 12:50 PM

+1 for wrong argument. When I was a college sophomore learning thermo I didn't care about the prediction of human metabolic rates using population statistics. I do now.

Medium avatar

(10611)

on March 07, 2012
at 12:41 PM

Oops - my response is to poisson.

Medium avatar

(10611)

on March 07, 2012
at 12:34 PM

I know because I've tried it Karoliina. My body does not defy the Harris Benedict equation for BMR. I could believe variation as much as 20% in the human population, but not the 1000% scenario you propose.

Medium avatar

(10611)

on March 07, 2012
at 12:29 PM

My N=1 found that it was true when I was losing weight. Human metabolic rate information is compiled from population data using statistics. The Harris Benedict correlation prediction for my resting metabolic rate was remarkably accurate. There's a big difference between the Chemistry 101 view of how thermo should work and how thermo actually works on humans.

Aa5e411ac90ac543cdb7d06a812a908d

(446)

on March 07, 2012
at 12:26 PM

Yes, I know it's not *only* about calories in vs. calories out, but come on now - 10 000 kcal a day? Maybe you can eat more now than you used to, thanks to butter and coconut oil or whatever, but there will be a point when too much is just too much and your body will start storing it as fat. You are free to prove me wrong, though - why not conduct a 10 000 kcal/day experiment on yourself? ;)

Ef089e1180f240aa9fd2d089f7f38b45

(279)

on March 07, 2012
at 12:16 PM

@Karoliina: How do you know? What about if those 10,000 calories worth food change your metabolism and fat processing? I'm usually above 5,000 daily (thanks to butter and coconut oil) and I am still as skinny as ever. For some people, the number of calories just doesn't mean anything, it's more about what they eat.

Aa5e411ac90ac543cdb7d06a812a908d

(446)

on March 07, 2012
at 12:11 PM

But if you go for the former, you aren't going to lose any weight...

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 12:03 PM

Respectfully submitted-This is incorrect. The first law applies only to closed systems. See answer below. If I were to turn in a paper that used the first law on a human to an engineering prof, the prof would hand it back without scoring it!

E28c3946e67c97bdb18d65eef3ef4ee0

on August 13, 2011
at 11:29 AM

Just the right answer.

Medium avatar

(10611)

on August 13, 2011
at 02:55 AM

Disciplined eating worked for me to lose 50 pounds and keep it off. Trust in feelings of satiety was what made me obese. I blame it on age, which reduced my metabolic rate. You can't eat like a 25 year old when you hit 56 unless you are very active.

Medium avatar

(10611)

on August 13, 2011
at 02:43 AM

CICO is a model which uses a simple thermodynamics model on empirically tested observations. It's not limited to eating, since activity affects metabolism. And according to the population models, metabolic rates increase as weight increases. This may break down at obesity, but it is accurate across a pretty wide range of BMI.

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12 Answers

9
510bdda8988ed0d4b0ec0b738b4edb73

(20898)

on August 12, 2011
at 08:58 PM

Um, the first law of thermodynamics applies to the entire universe. You can't say just because something is not simple the law doesn't apply to it.

Let's go with the statement of the first law:

The increment in the internal energy of a system is equal to the difference between the net increment of heat accumulated by the system and the increment of work done by it.

the "net increment of heat" is the energy in (food) minus the energy out (poop, water in your breath, sweat, etc), and the "work done by it" is you moving around (exercise). All the energy is accounted for there.

Seriously though, physicists came up with this stuff back in the 1800's do you really think something like the human body would be one of those things that 1) doesn't fit a well known law and 2) no one found out about it until now?

510bdda8988ed0d4b0ec0b738b4edb73

(20898)

on March 07, 2012
at 07:49 PM

"You can't account for biological changes due to the food chemistry itself changing the system." Yes you can! That's what 90% of chemistry is, accounting for the energy changes during chemical reacions (and biology is nothing but chemical reactions). My entire thesis was watching where energy goes during complicated chemical reactions.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 01:19 PM

Dude, I spent two semesters with this stuff! It only applies to a closed system. My coop is right. I know what you are getting at though. If you did have a way to fully account for all the chemical processes going on inside, you may eventually come up with a very complex model that can work. This is part of the reason why we have the second law. People just abused the first law and it went too far. The equations people are using from it are wrong. True story.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 01:25 PM

To make this a bit more clear-There is a big difference when you are using a physical law for a thought experiment (hey this makes sense) and when you sit down and start doing the math. This is when you need to define and understand your boundary conditions and define the system your equation is working. To say the entire universe meets the first law is trivial. No equation. Duh. Now write one for a human, and show the chemical storage inside in/out/converted in the math. No one is doing this that I can find. I saw a few attempts at it though. Again, this is what the second law is for.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 04:57 PM

What? I proposed no such thing. What you keep saying only applies in theory. Show me the math. You can't. It does not exist. Sit down and try writing the equations if you can't understand it any other way. What formula will you use for hormone conversion? Haha

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:35 PM

You're proposing an open system that doesn't fit a closed system equation. Of course, it fails.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 07:21 PM

I think the problem is you guys are really just arguing that there is no such thing as a open system. If the law holds, delta E = 0 anyway. So what? The engineer's use of open system means that when you get out your pencil to actually do the thermo, can you identify your system in such a way that energy in and out can be accounted for? You are saying "its possible." I'm saying "Duh, but you can't do it! It's open."You can't account for biological changes due to the food chemistry itself changing the system."

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 12:03 PM

Respectfully submitted-This is incorrect. The first law applies only to closed systems. See answer below. If I were to turn in a paper that used the first law on a human to an engineering prof, the prof would hand it back without scoring it!

510bdda8988ed0d4b0ec0b738b4edb73

(20898)

on March 07, 2012
at 06:20 PM

Whoa! I missed this whole fight going on in my thread. Exciting! DFH - you're totally wrong here. Any system, open or closed, contains the sum of the heat (energy) that went into in minus the heat (energy) that went out of it (Accounting for what goes in and what goes out is non-trivial). In a closed system, deltaE is 0, so its not even worth talking about. You may have spent two whole semesters on this, but I'm a Ph.D. in Chemical Physics and have had YEARS of statistical thermodynamics. Don't get in over your head.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:08 PM

DHF, you're mistaken. If you account for all inputs and outputs, energy balance must be achieved. That is the first law.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 03:56 PM

No, you don't. I don't believe you. You are in over your head.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 04:01 PM

I actually had some training in chemical engineering. Inputs, ouputs, heat transfer, boring, boring math, but very applicable to what we're talking about. What you're currently proposing is a one input, one output system. Of course, that fails, because there's multiple outputs, the input itself affects the output, etc...

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 03:28 PM

I'm a chemist, I can do the math, I understand the system.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 07:13 PM

miked-You don't seem to understand something. We all know "conservation of energy" holds. But, when writing and equation to actually do something with it, you need to identify a closed system or pick another approach. What your Phd didnt tell you is that some of that energy in the human system is going into changing the system itself. It/s not steady state. You can't write a formula for that. That's why the second law doesn't hold. You don't have access to everything you need to completely describe the system. Even phds can learn from lowly mechanical engineers sometimes.

510bdda8988ed0d4b0ec0b738b4edb73

(20898)

on March 07, 2012
at 07:48 PM

Dude, you are so wrong it's not even funny. I don't know why I'm arguing with you. Yes, some energy is going to change the state of the system, that's fine. But all of those changes are chemical reactions of some kind that will either take or store (chemical energy). I repeat (for the last time): the TOTAL energy of ANY system (including the human body) is the SUM of the energy the went into it minus the energy the went out of it. Internal changes can take or release energy, but it has to come from/go somewhere. Just because the equations are complicated, doesn't mean they're not true.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 01:54 PM

Matt, again. Don't get in over your head. There is a difference between your thought experiment and actually sitting down to do the math on a human as a system. I know the side you are taking and it's just a thought experiment. Do the math.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 08:12 PM

And you don't know the basics. No wonder you people never get anything built! http://en.wikipedia.org/wiki/Thermodynamic_system#Open_system

5
E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 11:47 AM

I was about to post this question and found this one on search and noticed that the top answer is incorrect, so this is to bump it.

I gave this question to our engineering coop at work (who is into leangains) and he hacked it in 20 minutes with diagrams. Smart kid.

The first law of thermo has fine print, and people didn't read the whole law!

The first law, conservation of energy, only applies to a closed system. Humans eating, pooping and living are not a closed system. There are more chemical processes going on inside that do things with energy that are not observable from the outside.

Much of nutrition and fitness use the first law as literally true, and they are all mistaken.

It's actually pretty close in the long run, but it's still the wrong argument.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 02:34 PM

I think we are on exactly the same page. Health folks used the first law wrong and ran with it.

24df4e0d0e7ce98963d4641fae1a60e5

on March 07, 2012
at 01:48 PM

Nonsense. You're an engineer right DFH? You should know better

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 01:52 PM

Matt- that isnt being done. Your answer could work in theory, but again, the problem you run into is why we have a second law. Don't get in over your head.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:22 PM

If you ignore certain outputs (heat, waste, etc...) you will necessarily violate the first law, because you're making it into an open system. Account for everything and the body is a closed system, first law rules it.

Medium avatar

(10611)

on March 07, 2012
at 02:42 PM

In my field the people with the government funded similarly non-useful results. The empirical expressions developed at the same time are embedded into all performance predictive models used commercially. The friction between the two groups was useful for discussion but the theoretical approach is now completely forgotten.

Medium avatar

(10611)

on March 07, 2012
at 12:50 PM

+1 for wrong argument. When I was a college sophomore learning thermo I didn't care about the prediction of human metabolic rates using population statistics. I do now.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 01:50 PM

Yes, I'm an engineer, and what I said was not nonsense. Engineers actually take "laws" and do the math!

Medium avatar

(10611)

on March 07, 2012
at 02:17 PM

Again DFH wrong argument. Sophomore physics are inappropriate to explain very well documented physiology. In the field I work in, fundamental physics principles were used to explain the structural mechanics of boxes. This approach failed miserably,but was solved simply and fairly accurately using population statistics in empirical correlations using the known important factors. The same applies to applying thermodynamics theory to solve a problem already well explained with statistics. Wrong tools produce only crude approximations.

5
7dc950fc76a046048e683d2a27dced37

on August 12, 2011
at 08:49 PM

I'm gonna let the good Dr. Feinman take this one:

We review here some aspects of thermodynamics that bear on weight loss and the effect of macronutrient composition.

E28c3946e67c97bdb18d65eef3ef4ee0

on August 13, 2011
at 11:29 AM

Just the right answer.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 02:00 PM

Some of the energy going in stored as chemical energy gets converted the body, and to changes how the body works. The reactions inside your body that change how food is processed are process enablers. Process enablers change the machine you wish to study. (Example, doing low carb to increase fat burn is a process enabler) For this reason, its not a closed system. All the tech articles that use the first law that I can find do not take this fact I to account. Everyone seems to be making the same mistakes.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 08, 2012
at 02:22 AM

Why do you keep repeating such a trivial thing? You haven't worked out HOW to do it. Lets look at the wikis (not authoritative, but hopefully neutral): http://en.wikipedia.org/wiki/First_law_of_thermodynamics (note reference to closed system). Now look here: http://en.wikipedia.org/wiki/Thermodynamic_system#Open_system By their definition, food in/out is open system. First law FORMULAs do not work on an open system. You don't have a first-law based formula to account for everything going on. No one does. To say "it's possible" is not an answer.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:16 PM

It is correct that different nutrients have different biochemical energy yields. Thus a calorie is not necessarily a calorie in a biochemical system, but that little to do with the second law. It's more of a problem ignoring some forms of energy and incomplete equations.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 04:05 PM

That's not the definition of a closed system. But let's talk about the energy conversion. A gets converted to B. There's going to be a loss in energy between B and A. In the exothermic reaction, heat is lost to the surroundings. In the endothermic reaction, heat is input into the system. And then there's the reaction byproducts produced, you have to account for the energy in those as well. And here you go, you can balance the equation.

3
C33e8c236e72d67c4b6c028401d23cce

(1884)

on August 12, 2011
at 10:37 PM

What most people don't take into account is that calories in-calories out is the last step in the causal chain. Trying to make it the first step is why people think it doesn't work.

1
8949bf87b0e0aefcad10f29975e4fa2b

(8989)

on August 13, 2011
at 02:20 AM

Yes, it applies, because it is a law. But, it isn't really all that applicable to obesity because we are not perfect systems. The CICO model assumes many things. One, that we can extract all calories equally, and extract them with an equal amount of energy input. But, really, does that make sense? We don't have to do all that much to digest sugar, but we have a whole digestive apparatus set up to deal with breaking down proteins, especially. Another big issue is that all the CI do not get translated into usable CO in the same way. Thin people throw off energy in the form of fidgeting, while fat people throw it into their fat cells. No law of thermodynamics is broken here. Thin people get hungry and eat, while fat people get hungry and have to eat even less because they have lowered their metabolism. This makes it look like CICO doesn't work. The real issue is not CICO, but how sometimes our bodies figure out how to balance it all (through appropriate eating signals, throwing off the excess, etc.) and for some of us, we don't balance it well. And since we aren't static, closed systems, the results do not match perfectly to the theory.

Medium avatar

(10611)

on August 13, 2011
at 02:43 AM

CICO is a model which uses a simple thermodynamics model on empirically tested observations. It's not limited to eating, since activity affects metabolism. And according to the population models, metabolic rates increase as weight increases. This may break down at obesity, but it is accurate across a pretty wide range of BMI.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 02:45 PM

Matt- see above answer regarding process enablers inside the body. They change the system. It doesn't work. Let it go.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:19 PM

CICO only "fails" when folks oversimplify it. If you start taking into account the actual energy extraction from food (i.e. your poop still has chemical energy) and differences in biochemical energy yield from different sources (thermic effect of macronutrients), CICO works.

1
Medium avatar

(10611)

on August 13, 2011
at 12:27 AM

It's only "sort-of" thermodynamics based on population statistics and empirical testing of activity and food. Look at how glycemic index is derived and you get an idea. A set of 10 student eaters (minimally paid) are fed, then their glycemic response is measured 2 hours later and the results are tabulated. Repeated tests produce variable results, but rice, glucose and wheat always come out high no matter how they're prepared.

I've thought about having my RMR tested to see how closely I conform to the Harris-Benedict population model. A few years ago I was counting calories carefully (both food amd activity) and losing weight, and I back calculated my RMR using the standard 3500 calories per pound over a period of a month. The number was within 5% of the H-B equation prediction. I thought maybe I was a special thermodynamic case, but I'm just run of the mill.

0
5945a4f7139d5a9c67265451d61ca069

on May 18, 2013
at 05:54 AM

I'm really sad this thread doesn't have more. I Love this discussion on calories in vs calories out. 1st law applies to everything, but means less in the real world of us humans. There is variance amongst people for calorie expenditure but so there is nutritional lying or underreporting. When coaching people who have trouble losing weight, i tend to always think of underreportinv calories, but these days I only think that after they've improved their food quality.

0
77877f762c40637911396daa19b53094

(78467)

on March 07, 2012
at 05:38 PM

You can turn thermodynamics on it's head with thermal loading. It's about the only way there is to increase the 'calories out' portion of the equation. www.hypothermics.com NASA figured it out, you can too!

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 06:16 PM

We discovered that its great fun working on rockets until the money runs out!

Medium avatar

(10611)

on March 07, 2012
at 06:11 PM

I see that your link goes to a set of dietary recommendations. I'm not following those rabbit trails to see where they lead. But please tell us what NASA discovered besides Tang.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 06:04 PM

"turn thermodynamics on its head?" I worked at NASA too, and we didn't do that! :)

Medium avatar

(10611)

on March 07, 2012
at 06:02 PM

You forgot about exercise Max. That's the most Paleo way to increase calories-out. Grok had to be out hunting-and-gathering to survive, metabolizing 70 kcal over and above his RMR for every mile he covered.

0
97d945680ed363e4cce48666d41c586e

on March 07, 2012
at 05:21 PM

Isn't conservation of mass more important?

0
32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 03:57 PM

The problem with the problem with CICO is oversimplification. Oversimplifying any system can make it appear to produce very counter-intuitive results. Be sure to balance your energy equation with things like:

  • Digestion inefficiency, i.e. how many calories are in your poop?
  • Thermic effects of food, i.e. How much energy is lost as heat during digestion of various macronutrients?
  • Effect of food ingested, i.e. how it affects metabolism via hormonal pathways.

It goes on and on, as you start not ignoring variables, inputs and outputs, you get more and more accurate representation of what is actually going on.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 04:26 PM

It's becoming more and more obvious that you're unwilling to account for all the inputs and outputs in the system. It's not a simple system that we can be sure of. Propping up an oversimplified strawman does not however invalidate the basic idea behind CICO.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 06:03 PM

You misunderstand. You are promoting a calculation no human has ever made as a defense for using the wrong formula. Occam's razor. Any luck finding an example of what you keep proposing? You can't.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 04:05 PM

Yes, and no. The problem with your answer is it doesn't matter. Since this in in the context of the incorrect application of the first law, where I shot down your lack of understanding already, it does no one a bit of good to salvage it. The reason we do not use the first law for problems like this is because of problems like this, but you are only trying to salvage it. Sophomoric.

E0250b1e6dc5ec1539ffb745042b4d80

(3651)

on March 07, 2012
at 04:23 PM

Mark-How about you find one example of the first law correctly applied with food consumption in scientific literature, per your simple thought experiment. That should be easy if you are right. You won't find one though. I know people have tried because I saw them. None of them can even get close to modeling process enablers that change the system internally, because all of them are not even understood, some not discovered yet!

0
Ef089e1180f240aa9fd2d089f7f38b45

(279)

on March 07, 2012
at 12:00 PM

If you wanted to lose weight, would you rather eat 10,000 healthy calories a day or 1000 of unhealthy calories including chemicals such as endocrine disruptors?

I would go for the former.

Medium avatar

(10611)

on March 07, 2012
at 12:34 PM

I know because I've tried it Karoliina. My body does not defy the Harris Benedict equation for BMR. I could believe variation as much as 20% in the human population, but not the 1000% scenario you propose.

Aa5e411ac90ac543cdb7d06a812a908d

(446)

on March 07, 2012
at 12:26 PM

Yes, I know it's not *only* about calories in vs. calories out, but come on now - 10 000 kcal a day? Maybe you can eat more now than you used to, thanks to butter and coconut oil or whatever, but there will be a point when too much is just too much and your body will start storing it as fat. You are free to prove me wrong, though - why not conduct a 10 000 kcal/day experiment on yourself? ;)

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:27 PM

I agree that the way you eat affects the "calories out" part of the equation. But it's quite likely that Poisson is producing very nutritious poop, meaning they're simply not absorbing all those 5000-10000 kcal.

Medium avatar

(10611)

on March 07, 2012
at 12:41 PM

Oops - my response is to poisson.

Ef089e1180f240aa9fd2d089f7f38b45

(279)

on March 07, 2012
at 12:16 PM

@Karoliina: How do you know? What about if those 10,000 calories worth food change your metabolism and fat processing? I'm usually above 5,000 daily (thanks to butter and coconut oil) and I am still as skinny as ever. For some people, the number of calories just doesn't mean anything, it's more about what they eat.

Aa5e411ac90ac543cdb7d06a812a908d

(446)

on March 07, 2012
at 12:11 PM

But if you go for the former, you aren't going to lose any weight...

Cccb899526fb5908f64176e0a74ed2d9

(2801)

on March 07, 2012
at 11:22 PM

Or very oily poop, according to the suggested source of those 5000 calories...oof

0
Medium avatar

on August 12, 2011
at 10:19 PM

Mike's right of course, but I think "thermodynamics," "calorie-in/calorie-out," "if it fits your macros," and "just eat 500 under maintenance" are garbage as far as constructing a sustainable fat loss protocol. The big key is creating a significant amount of net lipolysis while maximizing satiety. Losing fat needn't involve any feelings of deprivation. Eating a trimmed steak and boiled potatoes vs. an isocaloric amount of burgers/fries has a massive difference in satiety.

Medium avatar

(10611)

on August 13, 2011
at 02:55 AM

Disciplined eating worked for me to lose 50 pounds and keep it off. Trust in feelings of satiety was what made me obese. I blame it on age, which reduced my metabolic rate. You can't eat like a 25 year old when you hit 56 unless you are very active.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on March 07, 2012
at 01:23 PM

Only Travis would bring satiety to a thermodynamics party. :P

Cccb899526fb5908f64176e0a74ed2d9

(2801)

on March 07, 2012
at 11:20 PM

Travis, have you ever been overweight? Those of us who managed to eat enough food to get to that state generally have a vastly higher satiety threshold than a naturally lean individual. This, I think, is where genetics may come into play; sure, you can starve anyone down to a certain weight, but even eating nothing but whole foods will leave an ex-obese 130 lb male (cough myself c. 2011) ravenous.

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