Calories ...

Bump!

One would think that the calorie or energy-balance denialists would have gotten a clue by now, but apparently this post needs bumping.  

If you make it through this post and still believe calories are some non-entity, that somehow insulin or any hormone can trump energy balance, I don't know what to say.

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Original Post Date July 1, 2013    Calories ...

... or joules or ergs or foot·lbs or BTUs or eV or ...

These are all the same thing folks.  They are all units of energy. That we use different terms in different contexts doesn't mean we are talking about different things.  It's like different languages, be it vida or leben or liv or อายุการใช้งาน ... they all mean life.

The bastardizing of basic science in the Paleo and LLVLC realms is both ubiquitous and unrelenting.  This is what prompted me to start this blog.  I could really care less about the diet fads that come along that are obvious quackery, but this community is built on "our science is better" or "we understand the science", so wouldn't it be nice if that science is correct?

It is difficult to convey how the first installment of J. Stanton's latest series reads w/o preserving at least some of his formatting, so I'll delineate excerpts with ~'s.

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What Is A “Calorie”, Anyway?

The dietary calorie is defined as “the amount of energy required to increase the temperature of 1 kilogram of water by 1 degree Kelvin.”

The dietary calorie is actually a “kilocalorie” = 1000 calories, which is why you’ll occasionally see it abbreviated as “kcal”.

It’s an obsolete unit: the “joule” is the modern unit of energy. There are 4.184 joules in a calorie, and 4184 in a dietary calorie (kilocalorie).

Problem: Our Bodies Don’t Use “Calories”

You may already see the problem here: a “calorie” is a unit of energy transfer. We determine the number of “calories” in a food by, quite literally, burning it and measuring how much heat it generates.

This is a bomb calorimeter.

Note: not equivalent to the human digestive and metabolic system.

         


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source

(Me)  The concept of the calorie is attributed to Lavoisier in the late 1700's.  His caloric theory of heat as a fluid has long since been disproved, but the calorie unit is used to this day.  It is defined as the energy required to heat 1 gram of water 1 °C.  Atwater did experiments to measure the metabolizable (by humans, in humans) energy from food using calories as the energy unit, and probably for no reason other than being very small, the capital "C" Calorie became the commonly used unit for food calories, where 1 Calorie = 1000 calories or 1 kcal.  

I think the bomb calorimeter here is more instructive to understand how this all works for analyzing food calories.  Let's say we put some sucrose in this contraption.  When you ignite and react it with oxygen, the reaction is called combustion.  This is a chemical reaction -- bonds are broken, releasing energy, and others are formed, re-storing some of said energy in the reaction products.  What doesn't get re-stored, is "released" into the environment (in this case the chamber) as heat.  This heat is transferred to the water, warming it.  The mass of the water, specific heat, etc. are factored into a calculation of this energy released in calories, or Joules, or whatever appropriate units.  This heat is called the "heat of reaction".

However it need not be heat.  Indeed what perhaps is the distinguishing feature of life, is that we have the active coordination of chemical reactions so that the chemical energy released by one reaction that would normally be "lost" to heat, is coupled to another reaction where it drives that energy-requiring process to completion.  The bottom line here is that a calorie is a measure/unit of energy, not "energy transfer".  In the bomb calorimeter, the chemical energy stored in the fuel, that is released in the oxidation reaction (where matter is transformed), increases the thermal energy content of the water, and we can measure this by the change in temperature.  Same calories, conversion in this context of chemical potential energy to thermal energy.

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Unfortunately, our bodies are not steam engines! They do not burn the food we eat in a fire and convert the heat into mechanical work.  Thus:

There is no biochemical system in our bodies whose input is a “calorie”.

Every metabolic pathway in our body starts with a specific molecule (or family of molecules), and converts it into another molecule—usually consuming energy in the process, not producing it.

This is why we must eat food in order to stay alive. The chemical reactions that build and repair each one of the trillions of cells in our bodies, from brain to toe, from eye to pancreas, require both energy and raw materials. The chemical reactions that allow our cells to perform their necessary functions, from transporting oxygen to parsing visual input to generating muscular force to manufacturing mucus and bile and stomach acid and insulin and leptin and T3, require both energy and raw materials. And the chemical reactions that allow our cells to communicate, via hormones and neurotransmitters, require both energy and raw materials.

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(Me) Say what? Yes, J, you are exactly right. Our bodies are not steam engines. And thank you for making the point that since our bodies do not attempt to convert heat into mechanical work, any steam engine entropy thermodynamics is irrelevant. I have made this point time and again, along with the fact that heat generation (e.g. thermogenesis) does not require the 2nd Law of Thermodynamics to explain. Thermal energy is but one term on the "out" side of the 1st Law.  Here's a hint:  ∆G = ∆H - T∆S. 

But...

Your "block text" is wrong, because calories are Joules are eV are energy.

Just about every chemical reaction in our bodies requires input of "calories"

...even those like glycolysis and fatty acid oxidation, that ultimately yield energy, need a little input to get things rolling.

And...

The second and third installments of the series largely have nothing to do with calories and metabolism.  They are more about specific foods, with the noted exceptions that deal with digestibility/absorption issues.  Stanton seems to believe that it is those who acknowledge the role of calories who are trying to complicate things, when it is he, and others like him, that are doing so.   When you focus on where you put the fat or the health impact of a calorie of food, it is to distract.  NOBODY is saying that a diet of all soda is equivalent to a diet of all milk is equivalent to a diet of all butter is equivalent to a diet of all potatoes.  When it comes to the low carb "science" however, calories are calories and there's nothing magical to weight loss on LC when it occurs.

Any Discussion of Calories Must Begin With Atwater

The 9-4-4 calorie factors are attributed to the work of W.O. Atwater in the late 1800's.  They weren't determined as is often misrepresented by Stanton and others, in a bomb calorimeter.  Atwater merely compared the human data to calorimeter data.  Not that a bomb calorimeter is not used today to determine calorie contents of foods, but the "Calories" were determined in human calorimeters.

The figure above is from The Elements of the science of nutrition (Lusk, 1917).  You can read that book online, but it's a bit cumbersome to do so.  I did screenshoot/compile/convert The Atwater-Rosa Respiration Calorimeter chapter to a PDF file.  You can request access here if you like, or read the book in Google.   They measured O2 & CO2 and heat generated by the human consuming the food, and long story short the food "Calorie" is a measure of the metabolizable energy for a human.  The factors are averages and estimates.   If you care to read from Atwater himself, may I suggest:  Food and Health (Atwater, 1889).  

Actually, I think everyone reading this SHOULD go read that Atwater article first before moving on.  What you will realize is that almost 125 years ago, none other than Atwater himself considered all of the various so-called problems with calories!   A few thoughts:

• As imperfect as Atwater's calories are, it is amazing how well they hold up in metabolic ward studies (the only ones that matter when testing this stuff) for a relatively wide range of macronutrient intakes.
• Atwater acknowledged the uniqueness of protein as a macro.  But the LC vs. LF issue is not about protein.  
• It is somewhat unclear to me whether or not the thermogenesis (heat evolved) from metabolizing the macros is already incorporated into Atwater's factors.  
• Atwater did pay some attention to the bioavailability of the macronutrients in foods.  
• Atwater's use of calories was in an attempt to equate the energy derived from food to mechanical work done by the human body.

That said, it has been acknowledged many times that Atwater's factors are imperfect.  Here are a few:

• The Atwater System of Calculating the Caloric Value of Diets (1944)
• The measurement of food and energy intake in man-an evaluation of some techniques (1980)
• Is a Calorie a Calorie? (2004)
• Accuracy of the Atwater factors and related food energy conversion factors with low-fat, high-fiber diets when energy intake is reduced spontaneously (2007)

The above is far from a complete list.  Indeed since it is still fresh in the minds of many, there have been a surprising amount of studies on the Atwater factor and almonds!  See here, here and here (the latter is cited by Stanton in his third installment, and has some interesting outcomes unrelated to calories that may be worth looking at further at some point.)

Could the calorie counts of foods be more accurate in order to provide better information to those who wish to work with calories?  Perhaps.  I'm not a big fan of that approach as I fear the same shenanigans that are "net carbs" for outfits like Dreamfields and Julian Bakery will be employed by makers of certain foods. For example, if whole almonds contain only 75% "net calories" will the makers of almond flour bars use that in reporting calorie content when surely the ground almonds have more available calories?  There already is a problem with reporting of fiber and the calories we can get from fibers (via bacteria) are variable.  So last time I checked some countries allow zero calories to be assigned to fiber, while others use the 2 cal/g average while others just report fiber as all other carbs at 4 cal/g.   Perhaps "maximum calories" is a better measure?  I don't know.

Still, as reported, calorie counts with the Atwater factors provide each of us with a means of quantifying our intake -- these factors of bioavailability are being used as a smoke screen to sell you stuff based on the utterly irresponsible notion that calories don't count.  That is just not true.  They do, and if you are one of those people who is able to maintain a normal weight without needing to give an iota's conscious effort to intake, great for you, consider yourself lucky but otherwise please stop trying to convince people there's some magical diet out there that will do the same for everyone.  It doesn't exist.   I'll save further thoughts in this vein for a followup post.  

For now I want to discuss the "calorie" in your body.  Yes, we use a small fraction of our dietary intake for repair and maintenance and sometimes lean mass growth, but the vast majority is used to generate the energy required to fuel all of these processes.  As such, various carbohydrates, fatty acids and amino acids can feed into sequences of chemical reactions whereby they are broken down to CO2 and H2O and other small molecular fragments that are excreted generally in the urine.  Perhaps one day I'll tackle the protein metabolism in greater depth, but let's cut to the chase -- the argument is over oxidizing fats vs. carbohydrates for energy and some magical role of insulin in causing fat to accumulate.  

Our bodies are, in the end, biochemical machines requiring energy released from one reaction to provide the energy required to allow another to progress.  The currency for all of this is largely adenosine triphosphate, ATP.  Both fats and carbohydrates are broken down to create acetyl-CoA.   These processes differ, and again I'll leave that for another day, but one point I've made repeatedly is important here:  

Once you've got acetyl-CoA that enters the Krebs Cycle (aka TCA) all biochemical reactions and processes are the same. A molecule of acetyl-CoA generates 12 ATP via Krebs&ETC.

The mitochondria ultimately generate ATP and they are like the power company that delivers electricity to you.  You need a certain amount of electricity to power your lights and appliances, your body needs ATP to power all of the processes in your body.  And here's where Atwater obviously got something right.  Whether you call it calories or ATP-units, the amount of chemical energy contained in your average fat (9 cal/g) to carb (4 cal/g) is a 2.25:1 ratio.  How about for palmitic acid (common SFA) vs. glucose?  The ATP ratio comes out to 2.24:1    (Glucose: [38 ATP/mol] / [180 g/mol] = 0.211 ATP/g , Palmitate-TAG: [407 ATP/mol] / [860 g/mol] = 0.473 ATP/g , So gram per gram, the fat:carb ATP ratio = 0.473 / 0.211 = 2.24).   

The thing about oxidation reactions in our bodies, unlike the combustion of a hydrocarbon fuel with oxygen in an engine or open air, is that the reactions necessarily go to completion (or we have problems and large byproducts accumulate -- e.g. you "own" that mass!).  This is for a few very simple reasons:

• Enzymes catalyze reactions by a variety of means, not the least of which is by attracting and attaching to molecules to bring them into proximity to one another to facilitate the reaction.  This would be roughly like a group of singles being paired off by a match maker (based on similar traits, etc.) vs. blindfolding those people in a room and relying on them to pair off with their best matches by serially bumping into one another.
• Biological membranes prevent the flow of molecules of a certain size and structure across them.  Your body is like the Hotel California for the large molecules you ingest, only they can leave in pieces ;-) ... Imagine a combustion engine that can only let out CO2, H2O and perhaps a few very small number of small fragment products.
• Biological reactions tend to be pathways with a commitment step -- once the raw material is "sucked in" it is passed down the line and processed like there's no going back on a waterslide.

In your basic combustion engine, uncombusted fuel and combustion products other than CO2 and H2O are formed and make their way out the tailpipe.  This doesn't happen in humans, healthy ones at least, to any large degree.  If our biochemical fuel is not "burned" completely, the byproducts build up and cause problems (sorry Sam and Jonathan, but that sink clog isn't from sugar ...), but unlike combustion engines, fuel that is not burned at all is returned to the gas tank (e.g. fat stores)!

Therefore folks like Taubes and Stanton and countless others can talk about horizontal growth disorders and how meaningless calories are, etc.  They are all just blowing steam and clouding up your windows and glasses so you can't see the quite simple truth.  Insulin cannot get you more than 4 calories of energy out of a gram of carbohydrate.  All insulin does is manage the metabolic traffic so that the least efficiently stored energy sources are used first.    Insulin doesn't accumulate fat in your fat cells unless you are consuming more calories than you are expending -- averaged out over time.  

Hormones can't force storage in the face of sustained deficits, and they cannot "blow off" sustained excesses.  They can't create more or fewer ATP from a given fatty acid or hexose (6 carbon sugar such as glucose or fructose).  Those calories are calories are calories to a baby or Grandpa, to a diabetic or Michael Phelps, to a celiac or an alcoholic.

I will address metabolic adaptation in depth another time.  For now we're talking calories from food and this is what us "Calorie Wizards" are saying.  Truth and fact.  You have to be in energy surplus to gain weight and deficit to lose weight.  There are some dietary factors that dictate how much of that weight is fat vs. lean, but this appears to be largely dependent on protein and activity.  And it's a lie that carbohydrates  + high insulin favors energy storage as fat while fat + low insulin favors energy usage.  In the end, our carbohydrate stores are so small as to be negligible in determining long term energy balance.  We get fatter if we eat more calories because fatty acids have high energy density, and we store them in fat cells because that's what they are designed for.  When you are in caloric surplus to the tune of 3500 calories, roughly one pound of lipid is deposited, hopefully in your fat cells.  How this exactly equates to a pound of adipose tissue or other tissue it might be deposited in and/or associated water weight is where the fuzziness comes in, but this doesn't change the nature of calories and energy.  There's no magic.  

We all metabolize carbs and fats in exactly the same way...

... through the same metabolic pathways.  Metabolic ward studies have demonstrated time and again that manipulating the macronutrient composition ( with little variation in protein) of the diet does little to change the overall energy balance.  If you switch from a highly processed diet to a mostly whole foods diet, you'll probably lose weight.  Because a calorie is still a calorie, and your body likely absorbs a bit fewer when tasked with extracting them from complex biological matrices.