That’s because a calorie is simply a defined unit of measure: a measure of heat. So, just as all meters, ounces, and hectares are fully fungible amongst members of their class with each being indistinguishable from another, so it is with calories. More specifically, when referring to calories in the context of food, every calorie in the world represents the amount of energy required to warm one gram of air-free water from 14.5 °C to 15.5 °C at standard atmospheric pressure. If that were all there was to the story, then we could move on, but unfortunately, our work is not done yet because there exists an entire school of thought out there that extrapolates from this equivalence and pushes the thermo-chemical calorie into territory where it was never meant to go.
When people say that “a calorie is just a calorie”, they aren’t alluding to the above definition. Rather, what they mean is that the macronutrient source of a given calorie is irrelevant. Whether you derive 2000 kCal of energy from fats, protein, carbohydrates, or some admixture of the three, from the point of view of your metabolism, all possible combinations will be fully equivalent, assuming you maintain the same overall net caloric intake. This common understanding is far more interesting, principally because unlike the thermochemical definition in which the equivalence is tautologically true, the common view of caloric effects on metabolism is controversial, and that has made several authors quite a tidy sum as they argue for or against the premise. Those arguing for full caloric equivalence go about it in a manner something like this:
While fairly typical of the breed, as far as arguments go, this isn’t much of one. I expect that you have seen some variant of this sort of assertion and the very fact that it is repeated so often and from so many varied sources lends it the air of credibility. As a proof technique, this is known as proof by repeated assertion – just hammer the point until resistance collapses. It is also helpful if you can have multiple, hopefully seemingly unrelated, sources do the same hammering of the point. Rote learning works like this. You wind up “knowing” things without giving a thought to the derivation or underlying logic supporting those things, which is precisely the problem : by virtue of the frequency of repetition of such arguments espousing the equivalence of calories, most of us have become inured to the glaring and unwarranted leaps in logic contained at their core.
It is quite remarkable that the exemplar we have above consists of only three sentences and by my count contains no less than eight fallacies! That is an impressive error density, even the biblical apocalypse makes do with a mere four horsemen, and if this were the error density Olympics, I’d say we were looking at a gold medalist. Notwithstanding that, allow me to re-frame the assertions to explicitly reveal the contained error virtuosity:
With that done, I am hoping that the problem becomes readily apparent : you are not even remotely like a bomb calorimeter … which leads us nicely to the first fallacy.
Some of you may have been wondering about that definition of a calorie given earlier, specifically wondering why it is given in terms of raising the temperature of water. This is the end result of how the process of calorimetry is performed, and to help us understand that process, we can take a lesson from NASA.
On January 17, 1967, at 1:00 PM, EST, astronauts “Gus” Grissom, Edward White II, and Roger Chaffee entered the Apollo 1 command module for a launch simulation test intended to determine how the spacecraft would perform when operating under its own power. After several hours of testing, at 6:30:54 EST instruments recorded a voltage transient in the command module. Thirteen seconds later Grissom reported a fire. The flames quickly engulfed the spacecraft and tragically, the entire crew perished from injuries sustained in the inferno.
The subsequent NASA investigation determined that electrostatic charge build up caused by the friction of the astronaut nylon pressure suits moving against the nylon fabric of their seats had most likely been the ignition source. The resulting discharge when the astronauts grounded themselves by touching any of the aluminum panels in the capsule would have caused a spark with sufficient energy to start the fire. This is an impressive display of fire forensics, but if you live in an arid or cold climate, you probably have more than a passing acquaintance with electrostatic discharge and the very fact that you are sitting out there reading this right now is testament to an undeniable observation: in general, things do not spontaneously erupt into flames as a result of static electricity sparks. But in the Apollo 1 fire, they did, in a spectacularly catastrophic and tragic fashion. Why?
The answer to that question lies in the composition of the air inside the capsule, which wasn’t air at all. Instead, the capsule was pressurized with pure oxygen. And in a high pressure oxygen environment, materials which are not normally highly flammable will burst into flames … materials like broccoli, for example.
It is this propensity for spontaneous ignition of materials in high pressure oxygen atmospheres that is a foundational aspect of the science of calorimetry, the measurement of the heat of chemical reactions. To achieve these measurements, scientists routinely make use of a device known as a calorimeter to fully combust materials and measure the amount of heat ( energy ) derived. A calorimeter fundamentally consists of a combustion chamber immersed in a water bath. A few grams of the combustible material are placed in the chamber which is immersed in water of a known temperature and mass. By measuring the temperature of the water bath as it rises over time due to the energy released by the combustion, it is possible to compute the energy released per gram of material. This explains why calories are defined in what on the face of it seems to be a rather counter-intuitive way: “The amount of energy required to raise the temperature of one gram of water by one degree Celsius.” Once we put things in the context of how these caloric measurements are actually obtained, there is an inherent logic to the process.
Now you may think that you and a bomb calorimeter are on relatively equal footing when it comes to oxidizing materials, but I assure you, you are not, and to make that point, let’s take a look at what the typical calorimeter is capable of. According to the manufacturer of the Parr Series 1341 Plain Oxygen Bomb Calorimeter:
- Coal and coke, all varieties and types
- Fuel oil, both heavy and light varieties
- Gasoline, all motor fuels and aviation types
- Jet fuels, all varieties
- Combustible wastes and refuse disposal
- Foodstuffs and supplements for human nutrition
- Forage crops and supplements for animal nutrition
- Building materials
- Explosives and heat powders
- Rocket fuels and related propellants
Of all of the things on this list, the ones that should raise the most eyebrows are, of course, the foodstuffs, that pesky broccoli again, because unlike the other items, they seem uniquely unsuitable to combustion. Consider that due to the high water content of most vegetables, and most foodstuffs for that matter, generally you would be very hard pressed to get them to ignite, which explains why broccoli is not the preferred kindling for fireplaces. As the nutrient labs at the USDA tell us, broccoli is almost 90% water, which means that your calorimetry problem becomes as near as makes no difference: how do you get water to burn?
It turns out that this problem has been solved, and it doesn’t involve BP dumping an ungodly amount of petroleum into the Gulf of Mexico. All you need to do is to pressurize a chamber with pure oxygen at a pressure that is 30 times greater (!) than atmospheric pressure at sea level. If you do that, you can pretty much burn pure water. So that’s precisely what most bomb calorimeters do. When you ignite the atmosphere in such a chamber, the resulting combustion is so rapid that it is more explosion than combustion, a fact that goes a long way towards explaining how a bomb calorimeter gets its dramatic name. Who said science wasn’t fun?
Speaking of fun science, we need to take a small time out to discuss partial pressure, which is a measure of the thermodynamic activity of the molecules of a gas. Gases dissolve, diffuse, and react according to their partial pressures, and the partial pressure of a gas is determined by the other gases it is mixed with. At sea level, the partial pressure of oxygen is about 0.2 atmospheres, which is equivalent to saying that oxygen comprises about 20% of the gases we breathe in. This in turn means that pure oxygen at 30 times atmospheric pressure actually has a partial pressure 150 times higher than what we find in nature. That’s a fairly impressive scaling factor, but just to make sure we fully understand the magnitude we are discussing consider that if we take a man of average height ( 1.75m or 5’9″ ) and scaled him up 150 times, that man would be taller than the London Gherkin building, and only somewhat shorter than the Eiffel Tower!
For the obstinate out there that still insist that a bomb calorimeter pressurized to 30 atmospheres with pure oxygen oxidizing foodstuffs is equivalent to a human being, there is one more thing I should mention. Since the end product of combustion consists of heated gases, you cannot allow them to escape, because that would cause you to underestimate the heat generated by the materials in the calorimeter. As such, the calorimeter is a constant volume chamber, it does not permit the combustion gases to escape, which means the pressure inside the bomb only starts at 30 atmospheres and gets higher, much higher, from there. This produces tremendous pressures inside the calorimeter. The Apollo 1 capsule lasted 15 seconds after the fire started before rupturing, and if you think your digestive tract can come anywhere near withstanding these kinds of pressures, you are deluded!
The overarching point, however, is that in the bomb calorimeter model of energy extraction, the bomb is roughly the equivalent of your digestive system, and the water bath corresponds to the rest of you. This is a pretty abstract conception of how human beings operate with one fundamental, thermodynamically crucial distinction. Since everything in the bomb is physically separate from the water bath and the only exchange between them is heat, that makes the bomb calorimeter a closed thermodynamic system. You, on the other hand, are anything but a closed system, constantly performing work and exchanging both mass and heat with your environment. If you think that closed and open thermodynamic systems are equivalent, find a thermochemist and ask them, and if they maintain that they are equivalent, further ask them why then did experts in the field feel compelled to introduce the distinction?
The fundamental takeaway from all of this is that bomb calorimetry employs some extreme conditions in order to fully oxidize substances. This makes you and a calorimeter very dissimilar, precisely because it is impossible to reproduce the conditions created in a bomb calorimeter in a biological system, which means that when a biological system is necessarily generating energy, it cannot do so using high pressures, for instance. But once you start relaxing the bomb calorimeter conditions, lowering the pressure, the oxygen concentration, and so on, what you wind up doing is decreasing the energy yield of the process. Which means that all caloric values that you have ever seen based on bomb calorimetry represent a maximum bound on energy yield, and while you, as a biological system, cannot for all practical purposes extract that energy maximum, you can certainly extract much less, the question is, how much less? But according to ChocoTaco, 400 calories in a bomb calorimeter is 400 calories to the office worker enjoying a coffee, which is actually fallacy number two, energy extraction is perfectly efficient.
Michael Pollan’s Omnivore’s Dilema tries to answer the question, if you are an omnivore capable of eating just about anything, then what should you eat? Calorimetry can’t help us here because as a science, among other things, it is focused on a answering a rather different question : under idealized conditions, what is the maximum amount of energy you could possibly squeeze out of a substance? And when a thermochemist speaks of idealized conditions, (s)he means an environment where building and operating a bomb calorimeter has no associated energy costs. This is what we mean when we say that energy extraction is perfectly efficient. In this idealized world, pure oxygen at 30 atmospheres is free, free in the sense of not requiring any energy to produce or obtain, there are no parasitic losses in running the stirring mechanism which keeps the water bath in the calorimeter swirling around to bomb to make sure to extract as much of the heat of combustion as possible, and we don’t ask questions about how or where we got the energy to spark off the combustion reaction in the first place.
Ours is not such a world, so we do need to ask, just how much energy does it take to extract, and purify oxygen and pressurize the calorimeter bomb with it to 30 atmospheres? I do not have the precise answer to this question, and presumably, the answer will vary from calorimeter to calorimeter, but I do know that it’s far from zero. The equivalent of that 400 maximum calories of energy in our coffee is sufficient drive the industrial compressor below for about two and a half minutes. At that point, we’d better have managed to fully pressurize our chamber, because otherwise we are going into a net energy loss situation.
So it turns out that in the universe that we inhabit, not even a bomb calorimeter is capable of getting all 400 calories out of that coconut oil in the coffee, never mind the hapless office worker. Roughly speaking, biological chemical energy extraction runs on average around 65% efficiency, which would transform 400 calories into 260.
At this point, lets anticipate the rebuttal argument from the a calorie is just a calorie crowd: what practical difference does it make if we are dealing with 400 calories of sugar v. coconut oil or 260? The difference is actually crucial, and that is because it puts us in the realm of discussing net energy yield, not gross energy. And once we begin accounting for the cost of energy extraction, then that gets squarely into the territory of fallacy number 3, the assumption that the metabolic pathways for assimilating different macro-nutrients, fats and carbohydrates in this case, are identically efficient ( i.e. they have identical costs per unit of energy derived ) .
You really cannot fault people for fallacies 1 and 2. Those are rather esoteric for the most part, and the arcane aspects of calorimetry really aren’t part of general nutritional knowledge. Fallacy 3, however, tends to drive me up a wall every time it comes up, because it is so obviously and patently false, and, ironically, it stems from the one area where you and a bomb calorimeter are for all intents and purposes identical: neither you, nor a bomb calorimeter in any sense “eat” calories. Rather, both you and a bomb calorimeter derive calories from the processing of nutrients1 .
Scientists in the field of comparative nutritional and physiological research have long known that the processing of nutrients entails metabolic costs (reflected as an increase in metabolic rate), and further, that the effects are specific to both the given class of nutrient and the organism. In that field, the effect goes by the name specific dynamic action (SDA), and it makes perfect intuitive sense. After all, you have to ramp up your metabolism and expend energy to process whatever you just ingested, even if the only metabolic costs incurred is the elimination of an otherwise indigestible substance ( say you are toddler taken to eating dirt or paper ). It is this well known fact that has been twisted into the well-meaning but misguided eat many small meals a day tactic in the fitness world.
You may know SDA by the term that’s currently in vogue, the thermic effect of food (TEF), but whatever name you give it, the effect is well documented, with some of the earliest studies in humans going back to the 1920s. Take a look at the below table from McCue, I’ve highlighted the data for humans2 . The column we care about is CSDA(%). This shows us the percentage of the caloric intake that was unavailable to the organism because it was consumed by SDA / TEF. While the actual numbers are interesting, the most interesting aspect is the difference in the magnitude of the effect with different nutrients, with the difference between protein and carbohydrates being a factor of four … so much for the equivalence and fungibility of all calories.
Fallacy 3 is actually the lynchpin of the calorie equivalence camp, and dispelling it moves the discourse from talking about calories to talking about nutrients, and once we start talking about nutrients, we really hit our stride and the fallacies start falling fast and hard. Thus equipped with the calories aren’t nutrients crowbar, let’s use it to pry open the next fallacy via a small detour into the world of home renovation. I hope you’ll find it worth our while.
Your challenge, should you choose to accept it, is to build an addition to your home, and to get you off on the right foot, we are going to provide you with an unlimited budget! Now before you accept blindly and run off to the Home Depot with dollar signs in your eyes, recall that I did say that this was a challenge. Spending unlimited funds might prove a challenge once you’ve bought everything for sale in the world, but until then it really isn’t much of one. The challenge I’m proposing is that while you have unlimited funds to spend on the tools for building that addition, you are not allowed to spend one cent on building materials. So, any power tools, air compressors, all electricity or other energy costs are all approved for funding, but not a single cent for nails, wood, sheet-rock, paint, plaster, and so on. Now, that’s more like it, a proper challenge.
Should you accept this challenge you will quickly realize two things: 1) your only option for sourcing building materials will be to scavenge them from your existing house, so you will need to perform some very precise demolition, and 2) the scope of the addition that you will be able to build will be very very limited. Given these nearly insurmountable obstacles, I might be convinced to relax some of the terms of our agreement to allow you to have nails, staples, and maybe some screws. While an improvement, you are still sorely lacking in materials, so I don’t expect you to make much headway.
Let’s bring this back to metabolism and calories by laying out the fourth fallacy: nutrients only serve an energetic purpose. If this were true, you could survive on any arbitrary combination of nutrients, which, after accounting for SDA/TEF, would provide the same level of energy ( calories ). If you subscribe to this belief, then just as in the case of the home renovation challenge, I have the metabolic equivalent one for you. Eat a diet completely devoid of protein, but with an ad libitum amount of carbohydrates for, say, 60 days, then let me know of your results.
I think it is a safe bet that not even the most dyed in the wool supporter of caloric equivalence would be willing to eat a diet devoid of protein, given that the notion of essential nutrients is pretty well established scientifically. Of course, this implies that all calories are not equivalent, and the really interesting thing is to watch the back pedaling and rationalizations emerge when this implication is trotted out.
We still have four more fallacies to explore, which we will do in part two of this tome. In the meantime, let’s take a quick look around and see where all of this leaves us. It turns out, unsurprisingly, that the “all calories are the same” people are wrong, much like the Heisendiet “only the macronutrients count” camp is wrong. The reason this is unsurprising is because metabolism is complicated which makes it extremely unlikely that it can be reduced to a single dimension such as the caloric or macro-nutrient composition of the diet.
We need to be careful that we do not become quantification fetishists and lose track of the fact that the numbers are meant to be a simplified map of the underlying terrain. Where the map differs from the terrain, we need discard the map, instead of walking off the cliff because the map shows that there is supposed to be a bridge here, when in fact there is none. All in all, calorie counting is a crude tool, but so is body weight measurement, the BMI, the glycemic index, and so on. Nevertheless, they are all useful as long as we use them mindfully. This means realizing the inherent limitations of the tool, so if you find yourself using calorie tracking apps on your smart phone with impossibly precise caloric prescriptions, you should probably consider that you may have gone over to the calorie counting dark side.
To the extent that you consider most things a calorimeter oxidizes nutrients ↩
While the data for humans is indeed impressive and directly relevant, take a look at the dog data, it is absolutely stop-you-in-your-tracks fascinating. The first item of interest is that for a dog, there is a vast difference between the SDA of a small meal vs. a large meal of the exact same macro-nutrients! We already knew this and have talked about it here. However, if you do the comparative physiology bit, it becomes really interesting when you consider that dogs are carnivores, domesticated apex predator wolves. We humans are omnivores, meaning that our digestive systems aren’t particularly good at processing any specific nutrient class. It is therefore rather stunning to consider that for a small beef meal, we are 50% more efficient than the specialized carnivore in processing the meat, and our advantage gets even greater as the meal size increases! There are some very interesting reasons for this and implications as well. Something for another post. ↩
The man in the photograph is Werner Heisenberg, a name that might be familiar to you in the guise of the eponymous Heisenberg Uncertainty Principle, or you might know it from the name of the antihero protagonist of Breaking Bad.
The Heisenberg of Uncertainty Principle fame told us back in 1927 that when it comes to physical properties of a particle, there is a fundamental limit to what can be known simultaneously, so the more precise we are with respect to the momentum of a particle, for example, the less we can know about its position, and vice versa.
The layman’s form of expressing this idea comes to us as a joke about Werner Heisenberg who is driving along the highway when he realizes that there is a police cruiser behind him, indicating that he should pull over. He does, and the officer walks out of his cruiser and up to Heisenberg, asking him … “Sir, do you have any idea how fast you were going?” To which Heisenberg replies, “No, but I know precisely where I am.” This joke goes over really well in the lunch room at the Large Hadron Collider …
The uncertainty principle is often confused with a related concept in physics known as the observer effect which states that certain systems cannot be measured without changing them. If you think about it for a bit, this makes sense, and you probably run into the observer effect various times throughout your day. For example, in order to measure the inflation pressure of the tires on your car, you first need to release some pressure into the pressure gauge. But by doing so, you actually change the pressure in the tire, so your reading on the gauge is just an approximation of the actual tire pressure.
Now you may think that releasing a tiny bit of air pressure from a tire in order to measure it is not such a big deal, and I would probably agree with you, but the observer effect manifests in other contexts as well, more specifically when dealing with observing people, and in that context, it is often known as the Hawthorne effect.
Lessons from Western Electric
Over a period of several years, spanning from 1924 – 1932, workers at the Hawthorne plant of the Western Electric Company in Chicago were the subjects of several experiments relating to productivity and how best to improve it. Researchers experimented with altering various parameters at the plant to observe the resulting effect on worker productivity.
One of the parameters to be altered was the ambient light. Researchers reasoned that being better able to see what they were doing would improve worker productivity. And, sure enough, when the ambient light was increased, productivity increased. The effect, however, proved to be temporary and over time, productivity levels reverted to pre-intervention levels. This was unexpected, but the researchers had several other interventions planned, so in order to test those and eliminate the confounding effects of their previous intervention, they returned lighting to its previous levels, intending to leave it there for a period to get workers reacclimatized to the previous baseline conditions. Of course, they expected productivity to decline, or at least maintain … but the actual productivity improved.
It turned out that irrespective of the actual intervention, increasing or decreasing ambient light, increasing pay, changing the temperature inside the plant up or down, all the interventions tended to increase productivity, but the increases were short lived, and quickly reverted to the pre-intervention mean. Again, with perfect hindsight, this makes complete sense, people under observation behave differently from what they would normally do. Once they become accustomed or inured to the observer, they revert to their true form. Primatologists like Jane Goodall have made excellent use of this tendency of higher primates to study their true behavior by very slowly introducing themselves into a chimpanzee troop, for instance, and allowing them to habituate themselves to the presence of the researchers, at which point they revert to their true behavioral patterns.
The Weak Form of the Heisendiet Effect
These principles also apply to those who undertake to change their diets, even if this is not being supervised by any researchers. Even on self-monitoring diets, as for the Hawthorne workers, the mere fact that the diet is being observed will result in initial high compliance and adherence ( even over adherence ) to the diet protocol. But over time, as one becomes accustomed to the intervention, one regresses to previous patterns and behaviours.
This cycle plays out with alarming regularity every January 1, when untold millions undertake new dietary interventions, and irrespective of the merits of the actual approach, experience some initial measure of success, but fail to translate those successes into a long term transformations. This is the weak form of the Heisendiet effect: in the short term, most dietary interventions will have some effect for reasons potentially quite unrelated to the underlying mechanisms of the intervention ( e.g. you eat only potatoes and manage to lose some weight, but the weight loss is due to Heisendiet effects, not any particular beneficial property inherent in potatoes )
Often, the weak form of the Heisendiet Effect can be seen at work in settings where results are attributed to the placebo effect. As an example, consider this study :
These researchers told a group of room attendants that they were engaging in healthy exercise while at work and they observed improvements in health markers relative to other workers engaged in nominally the same activities who had not been informed that their work constituted exercise. This is all attributed to the placebo effect – “the informed group perceived themselves to be getting significantly more exercise” therefore ” … as a result … they showed a decrease in weight.”
In effect, the researchers posit that these ladies thought themselves thinner. Maybe so, but if this were true, then every single reader of “The Secret” ought to be a rail thin, six-pack toting, super-model bodied envy of all of her friends. I’m willing to bet that they’re not, and I suspect that’s because what was really being observed here was the weak Heisendiet Effect.
Even though the researchers claim that “actual behavior did not change”, it is important to realize that they did not monitor this in the slightest, rather, they merely asked participants to self-report whether they were doing anything differently, to which participants responded that they had not changed their behaviour. I suspect that the workers at the Hawthorne plant, had they been asked to assess whether they had changed their behaviours, would have also replied in the negative. Nevertheless, it is evident from the productivity changes observed that the Hawthorne workers did in fact alter how they went about their business. Accordingly, it is not difficult to imagine that those ladies who thought of their work as health inducing exercise might have gone about their daily duties with a little more vim and vigor. Perhaps, in light of their new found realization that they were getting more exercise, they might have also skipped a soda or two during the course of their day, or maybe they omitted the morning donut with their coffee? To me, this seems just as plausible a source for the results observed by the researchers.
The Strong Form of the Heisendiet Effect
On the whole, people behave in similar ways, meaning that most dietary interventions are subject to some degree or another to the weak Heisendiet effect. This is not something that we can do much about, so we’ll have to learn to live with it. The more pernicious problem comes from a sub-culture of dietary interventions that trades certainty regarding how much one should eat for specificity regarding what one should eat. This is the strong form of the Heisendiet Effect: disregard for caloric intake replaced with fanatical attention to nutrient composition or some other facet of the diet. Uncertainty by design.
The above quote comes from Jimmy Moore, a gentleman who has lost well over 60 lbs. while following a ketogenic diet. The interesting thing is that Jimmy attributes his success to the composition of his diet, not the energy provided by it. He is entirely focused on “the importance of being in a ketogenic state.” Accordingly, when he measured his ketone levels, he was dismayed that they were rather low, this despite the fact that he is quite happy with his body composition and weight loss achievements, so much so that he is a strong advocate for the ketogenic diet ( the one which he admittedly might not have been following for nine years )!
Jimmy is certainly not alone in this mind set, if you head over to Mark’s Daily Apple you will find a massive and growing forum thread discussing nutritional ketosis. Among the seminal advice offered to those wishing to undertake an “N=1 self experiment” with the approach, we find this regarding the importance of caloric intake:
Notice that calories may matter “in some ways for some people.” That’s pretty vague, to put it mildly, but typical for the strong form of the Heisendiet effect: we are absolutely certain that we need to “Eat More Fat!”, we’re just not sure that caloric intake really matters.
So What? People Lose Weight on Heisendiets All The Time
Actually, people in general don’t … some people do. Some ill-defined sub-group of people incidentally lose weight while utilizing a Heisendiet. Pebbles67 at Marks Daily Apple actually goes and makes this point explicitly when she admits that ketosis doesn’t work “in some ways for some people” who fail to lose weight despite gorging on fat. The approach advocated is basically random empiricism – try to eat more fat and if it doesn’t work, maybe you need to count calories.
Even for those select lucky responders to the Heisendiet, attributing their results to the actual intervention stretches credulity : Jimmy lost weight, but he was certainly not experiencing ketosis to the degree he thought he was. His weight loss, while real and measurable, seems to only be tangentially related to his ketosis ( or lack thereof ). There was some other mechanism at work.
The real problem with Heisendiets is that they are incoherent and unpredictable, precisely because they ultimately fail to identify the mechanism for the success or failure of the diet. As a result, they cannot answer very simple, practical questions, such as, how does one achieve weight stability? Lets assume Pebbles67 lost 20 lbs. while eating more fat on her quest for nutritional ketosis, and then she became weight stable. She achieved a plateau. How can we explain this within the context of the Ketogenic Heisendiet? Is she now producing fewer ketone bodies? Or perhaps she is somehow utilizing the ketones she is producing more efficiently? Of course, the concept of efficient utilization of nutrient substrates forces us to discuss energy, that is, calories, but remember, Heisendiets are pretty vague on calories, so let’s skip that. What if Pebbles67 wanted to lose an additional 10 lbs. of mass? Does this then require her to eat yet more fat than she already is? That sounds quite suspect, but it is in keeping with the advocated dietary approach.
You’ve got to ask yourself one question : “Do I feel lucky?”
So should you take a gamble and try one of these Heisendiets on the off chance that you are a responder, and furthermore, that the eventual weight plateau that you will reach will be at a point that you are happy with? If I were you, I’d probably try to find an approach that was consistent with what we know about metabolism, and what we do know about metabolism is that it is rather laser focused on energy, which might be a good place for you to start as well. I’m pretty sure that this body composition game comes down to very simple, essential basics : energy and appetite control.
Rob, a reader from Ireland, pointed me to a worrying post regarding the potentially negative aspects of intermittent fasting and asked about my opinon of it. Ok, I’m being generous here by throwing in the modifier potentially, because the post’s author definitely holds the viewpoint that fasting will kill you … I’m paraphrasing here and exaggerating a bit for effect, but not much since the actual quote from the posts’s conclusion is:
It has been said that extraordinary claims require extraordinary evidence, so, without further ado, let’s dive in to the “proof” of Kiefer’s pudding.
If you Can’t Dazzle Them With Brilliance, Baffle Them With Bullsh*t
Try as I might, I can’t follow Kiefer’s argument, mostly because I find it muddled and contradictory. Things start off on the wrong foot when he asks the reader to suspend all disbelief and “imagine a purely destructive process that’s critical for building the very thing it destroys.” Call me pedantic, limited, or lacking in imagination, but to me a purely destructive process only destroys, it doesn’t build. If it destroys and builds, then it’s not purely destructive, but rather, complex, subtle, and nuanced.
If you are in a charitable mood, you might be tempted to let Kiefer off the hook and chalk all of this up to enthusiastic overstatement – maybe he didn’t really mean that autophagy is purely catabolic. Except that apparently, he really does mean it as he repeats this mantra throughout his post : “by definition and function, autophagy destroys tissue, making it purely catabolic.” Not to nitpick, but even if we were to concede that autophagy is purely catabolic (it isn’t), autophagy does not destroy tissue. Autophagy is active at the cellular level, while tissues are collections of cells. This is a very important distinction for reasons that will become apparent later, I raise this issue here to point out that Kiefer might be a bit sloppy in either his understanding, or explanations, or both.
This stance on autophagy as purely catabolic is especially surprising when you realize that in his citations, Kiefer refers to a paper by Masiero et al. entitled “Autophagy is required to maintain muscle mass.“ I understand that Kiefer is a busy man as he is trying to build his nutritional conselling business, and he may not have had the time to read the full paper, or maybe even the abstract. But I would hope that he at least had the time to read the title! Trying to characterize something that plays a critical role in maintaining muscle mass as purely catabolic smacks of expending a lot of effort in pounding a square peg into a round hole.
But why is Kiefer doing this? After all, he’s not dumb, far from it, as he tells us himself, “he’s smart as f*ck.” Mostly, he’s trying really hard to create an association in your mind between autophagy and pure catabolism so that in the subsequent discussion, whenever you see the word autophagy, he would ideally like you to picture your body melting into a puddle of catabolic goo. Because if he can sell you this purely catabolic disease, he can then sell you his cure, and it will only cost you $89. The last thing Kiefer wants is for you to think of autophagy as complex, subtle, nuanced, and worst of all, tightly regulated:
More recent research has altered the original view of autophagy as a nonselective process by revealing the existence of molecules involved in selectivity of autophagosome cargos. … Autophagy is tightly regulated to prevent its unbalanced activation, which may cause damage to cells. Studies have identified at least two signaling complexes that participate in the fine-tuning of autophagic activity under conditions of stress and other physiological circumstances in which autophagy is needed.
Selective autophagy includes a pathway for targeting specific hydrolase proteins ( the Cvt pathway ), one for processing protein aggregates (aggrephagy), another for processing ribosomes (ribophagy), yet another one for mitochondria (mitophagy), as well as pexophagy, a pathway for specifically targeting peroxisomes. That is certainly a lot of pretty specific pathways. As Shakespeare might have said, “if autophagy be the food of the nutrient deprived cell, play on, give me excess of it!”
Over time, I’ve learned a thing or two from my wife, especially at mealtimes, when she habitually leaves her favourites to savour slowly at the end, so I’ve saved my favourite selective autophagy pathway for last – macrolipophagy:
If at this point you want to take some time to bask in the glow of the work of Singh et al., by all means, please take all the time you need. I’ll wait.
All of the mentioned pathways make use of macroautophagy, that is, the formation of a bubble-like structure within the cell that encloses the target of autophagy in what’s been termed the phagosome. The phagosome then fuses with another structure containing enzymes that lyse, or breakdown, the phagosomal contents. This is quite important to keep in mind, especially when Kiefer gets a hold of the phagosome and waterboards it into confessing to crimes it did not commit:
Kiefer’s mental model of autophagy seems to be that of a process that is turned off and on much like one operates a light switch. It isn’t. It is an ongoing process, the rate of which rises and falls in accordance with the cellular context and needs, but never actually “turns off.” But let’s ignore that for the time being in order the take a closer look at the paper by Mizushima et al cited as reference 7. We will be looking for a substantive demonstration that macroautophagy is something that treats fast-twitch muscle as exceptional, in the manner described by Kiefer.
In 2003, Mizushima and team published a paper where they revealed that they had figured out a way to make the autophagosome glow in the dark under UV lights. Like all children when presented with a cool new toy, they promptly set about making mice with glow in the dark autophagosomes so they could look at them and count them. Since they knew that a good way to increase the number of phagosomes is to restrict nutrients, they tested their mice in the fed state, after 24 hours of starvation, and lastly, after 48 hours to determine what changes in the number of autophagosomes per unit of surface area could be detected. This is what they found:
The first thing that ought to strike you is that each graph looks different from the others. Different tissues exhibit different responses to food deprivation. This is not unexpected as we know different tissues have different energetic needs as well as different internal structures and therefore different substrates available as autophagy targets.
The second thing that ought to jump out at you is that at time 0, in the fed state, all tissues exhibit varying levels of basal autophagy. Some tissues, like the pancreas, exhibit quite a high level of basal autophagy. In contrast, the heart has some of the lowest basal levels of autophagy recorded by the researchers, although even here they are not zero. So much for “turning off” autophagy.
The third thing that you ought to notice is that in almost all tissues that respond to starvation, including fast-twitch muscle ( EDL M. ) the rate of autophagy after 48 hours is actually lower than after 24 hours. The notable exceptions here are the heart and the soleus muscle, a muscle predominantly consisting of slow-twitch fibers. So, we can toss “macroautophagy stays on for 24 hours or longer only in fast-twitch muscle if we don’t eat” into the trash can too.
Lastly, note that in terms of the Thymus and Lens graphs, none of the observed differences were statistically significant, so, for all intents and purposes we can consider autophagy to be independent of the nutrient availability in these tissues over the timeframe under consideration ( i.e. nutrient deprivation over 48 hours. )
All of these observations put together ought to make you wonder how it is that one can claim that “macroautophagy is transient in nearly all tissues except fast twitch muscle” after having read this paper? It certainly gives me pause. The paper does show that for the most part, cells deprived of external nutrients turn to internal stores, which we knew was the case before we started, so, there is nothing novel here.
In and of itself, however, the fact that we observe the exepected increased autophagic activity, doesn’t tell us very much at all. What we need to know is: what materials are being broken down? Which autophagy pathway is being invoked? Are we talking about damaged organelles, toxic protein aggregates, intracellular parasites, in other words, expendable cellular garbage, or something else, like large supramolecular structures such as whole undamaged organelles of the cell? And if we are talking about whole undamaged organelles of the cell, how many of them are actually LDs, the cellular lipid transporters?
Suffice it to say that up to this point, I am left unconvinced by Kiefer’s argument, to put it mildly, and we’ve hardly scratched the surface. However, I do think that I’ve given you a lot to read and think about, so I’ll stop for now, or else this article won’t ever see the light of day. I’ve already rewritten it four times. It’s about time to publish it.
In closing, I would like to thank Rob for bringing this post to my attention. Ordinarily I would have replied to his email directly to thank him, but it turns out that my contact page was buggy, and did not provide me with his email address. This is now fixed, so I am doubly indebted to him. Cheers, mate!
This post has been a long time coming, and I’ve posted it in various forms, and bits and pieces in several internet haunts, but at long last, I’ve repatriated it here. When it comes to intermittent fasting, the amount of misunderstanding, misconceptions, and misinformation out there finally compelled me to put metaphorical pen to metaphorical paper here.
First thing first, just to get it out of the way, intermittent fasting is not a miracle cure for all that ails you. I think that there is a lot there to recommend it to people, I practice my version of it, and have been at it for coming on five years now, and I fully intend to keep doing it. I do recognize, however, that it cannot be all things to all people. If anyone tries to tell you that one size fits all, then you are dealing with a blatant charlatan and you ought to govern yourself accordingly.
What is intermittent fasting?
There is no clear cut definition, unfortunately, which contributes to the misunderstandings. Wikipedia maintains that “Intermittent fasting (IF) is a pattern of eating that alternates between periods of fasting (usually meaning consumption of water only) and non-fasting.” This definition is less than useless, as it practically suggests that eating the traditional three meals a day, and drinking water in between meals, which constitutes a pattern of eating alternating between fasting and non-fasting, is intermittent fasting.
For my part, I suggest that we adopt a pragmatic definition: “intermittent fasting is a pattern of eating that involves a greater interval between meals than generally culturally prevalent.” So, if you habitually skip breakfast, you are fasting intermittently by our definition. Skip breakfast and lunch? Great, you fit the bill too.
One thing ought to be glaringly obvious in this definition due to its conspicuous absence: nobody said anything about calories. Should you choose eat breakfast, lunch, and dinner all at 7:32 PM EST every day, then you are intermittently fasting by this definition. With that out of the way, we can dispell the first myth of IF – it is not starving. Starving yourself does fit within the definition, but it is a degenarate case. If you have some masochistic need to starve yourself and then call it IF, you certainly can, but the definition in no way requires it.
Why would you fast intermittently? The Intuitive Answer.
Going back to the intermittent fasting definition, at some point someone realized that to a large extent in modern society meals and meal times are culturally rather than biologically determined. It didn’t always use to be that way, and we have the linguistic archeological record to prove it. The word breakfast (as said by Sean Connery, the best of the Bonds in my opinion) used to define a functional meal, the one that broke your fast, even if that were daily at 7:32 PM EST. In modern society, the word has been co-opted and transformed from a functional definition into a cultural one where breakfast is your morning meal, generally consumed before heading off to work. I expect that this arose as a consequence of industrialization given that factories thrive on predictability and conformity. It is not clear to me that people thrive on conformity to the factory whistle, a point most eloquently made by Connery’s Bond who eats because he is hungry ( a biological imperative ), not because the time is appropriate for the meal ( a cultural imperative ). The question is then, what is an eating frequency that is compatible with a biological imperative?
Another intuition that helps us answer the frequency question is the realization that there is a continuum of possible feeding schedules, and most of it represents ridiculous extremes. Assuming we are aiming at a 3000 kCal diet, and sleep for 8 hours a day, we could eat 0.05 kCal for the 57600 seconds that we are awake. That is, we could literally be constantly eating, albeit a miniscule amount of food each time. This represents a practical upper bound on how frequently one could eat. For a practical lower bound, consider attempting to eat a week’s worth of food at one sitting, or 21000 kCal at one meal. Assuming that our diet consisted of the most energy dense food we know, dietary fat, we would need to eat 2.33 kg, or 5.1 lbs, of fat at this meal. Never mind the practical aspects of actually digesting this amount of fat, just the thought of attempting to do this is enough to revolt me. So, it would seem that a reasonable continuum has once a week at one end, and once a second at the other, with the true value probably being much more narrowly banded. I think enough of us know someone, or perhaps we are that someone, who does not eat breakfast because they do not feel hungry in the morning, even though they do not call that IF. Given this it is not much of a stretch to make the intuitive leap from not eating breakfast, to just eating dinner, as being a reasonable bit of the meal frequency continuum.
Why would you fast intermittently? The Appeal to Authority Answer.
Quick, name the first organized religion that comes to mind, and I’ll bet you that they have a tradition of fasting. Whether Christian, Buddhist, Hindu, Muslim, or Jew, people have been fasting for better or worse for thousands of years now. I really don’t have much to say about a religious justification for fasting, but I will say that in Islam, we have a population that fasts every year for the month of Ramadan, eating and drinking nothing between sunrise and sunset. Studying Muslim fasting populations allows scientist great insight into the effects of fasting on the human body, which brings us nicely to:
Why would you fast intermittently? The Scientific / Metabolic Answer.
One interesting aspect of fasting during Ramadan is that people tend to compress their eating schedule as the same quantitiy of food is ingested, but this is done in what amounts to one large meal in the evening. So, an interesting question to ask would be whether a greater interval betwee meals had any metabolic effect. It turns out that if you fast during Ramadan, you can expect:
- A decrease in LDL cholesterol, and a concomittant increase in HDL (as found in this study, as well as this one. )
- A decrease in serum triglycerides ( same source as above.)
- No change in your plasma cortisol concentration.
- No change in thyroid hormone levels (T3, T4).
- Lowered levels of homocysteine and C-reactive protein ( indicators of inflamation ).
- A pronounced lowering of insulin during the daily fast portion “favor[ing] a predominant lipolytic state.”
- You may experience some changes in body composition, but the studies are contradictory, although you are unlikely to gain weight.
Like I said, fasting during Ramadan has been extensively studied, and I could go on, but I think you get the point. I have linked to all of the studies, but unfortunately, only some of them provide the full text. The remainder are just abstracts, but worth reading, all the same.
In the above list, pay close attention to points 3, 4, and 5 because they relate to the hormonal impact of Ramadan fasting, and basically allow us to conclude that metabolically speaking, as far as the body is concerned, it’s all business as usual, if not better. I make this point because invariably, when discussing intermittent fasting in the form of only eating one large meal in the evening, someone will start frantically beating the “starvation response” drum. You can politely ask them how eating a day’s worth of calories in one meal can possibly constitute starvation, and then point them in the direction of the studies cited in 3, 4 and 5.
For me, this is absolutely fascinating because all you have done is monkeyed about with the timing of your meals, and derived a pretty good benefit from it for your effort. It is almost as though you may have gotten something for nothing. Almost, but not quite. Even the most basic understanding of the digestive process must include the realization that not all the things you put in your mouth are good for you. Consequently, a large amount of digestive energy is expended in performing triage, separating the desirable aspects of our diet from the undesirable, assimilating the good bits, and disposing of the bad. It would seem plausible that the observed benefits of Ramadan fasting might be due to the fact that the body is not continuously engaging in this metabolically taxing process throughout the day, but rather doing it all in one concentrated batch.
In the interest of full disclosure, I do not follow Ramadan style fasting insofar as I find the proscription on drinking during the day too strict. I understand that this means that the conclusions reached in the studies I referenced therefore may not apply to me, as the observed effects may be due to the drinking behaviour in conjunction with the eating. I don’t believe that this is the case, but my beliefs do not seem to affect objective reality, much to my consternation.
Stay tuned for part II …
That’s what the breathless headline blared from the cover of the celebrity tabloid at the magazine stand. Now, I’m not much for gossip, so I didn’t read the article. As a result, I am completely in the dark when it comes to what dietary strategy, supplements, exercise, or other tactics Kim employed to achieve this newsworthy outcome. I do know a few things about metabolism, however, and this gave me pause.
The implication of the headline is that the weight lost was fat, so naturally, we may ask what would one have to do in order to lose one pound of fat per day? By now, it is more or less generally accepted that one pound of fat is 3500 calories, so Kim would have had to create a daily caloric deficit in that amount. And how does one go about creating a caloric deficit? Well, everything boils down to a variation on two themes : eat less calories, or burn more of the calories that you are taking in.
Since I’m not really sure what Kim was eating, we’ll explore a couple of options with respect to her diet. We’re also going to need to be able to come to grips with Kim’s calorie burning activities. In order to estimate what kind of activity Kim had to engage in while trying to achieve her weightloss target, we’re going to use Metabolic Equivalent Units, or METs where one MET is equal to 1 calorie burned per kilogram per hour at rest ( 1 cal kg-1 h-1). Different activities have different METs levels, and they scale linearly, meaning that if you engage in a 10 MET activity, you are actually burning 10 calories per kilogram per hour, for a 13 METs activity, you will burn 13 calories per kilogram per hour and so on.
Kim is 5’3″ and weighs in the vicinty of 130 lbs. or 60 kilos ( I assume ). Our interest in Kim’s weight goes beyond salacious gossip, we only care about her overall mass because we want to compute her basal metabolic rate. As a bare minimum, assuming Kim is a creature of pure leisure and spends an entire day at rest ( 1 MET ) Kim burns 1 cal kg-1 h-1 x 60 kg x 24 h, or 1440 cal, well short of the 3500 calories she needed to dispose of daily in order to achieve her weight loss.
But of course, Kim hardly stays at rest the entire day. She presumably has other matters to attend to, so, we need to make some more assumptions about how Kim spends her day. Accordingly, assume that Kim sleeps for 8 hours, works for 8 hours, engages in leisure activities for 3 hours, household activities for 3 hours, and dilligently exercises for the remaining 2 hours. Armed with this, let’s consider two incarnations of Kim, Extreme Kim and Reasonable Kim.
Extreme Kim (EK)
Extreme Kim is goal oriented, analytical and very focused. She knows exactly what she wants and how to get it. She is a career woman whose work day is filled with meetings and intense bouts of “getting things done!” Since she set her mind on losing that excess weight, EK has decided to forgo eating entirely for the duration. There is no better way to create a caloric deficit than by not eating!
Since EK sleeps for 8 hours a day, she consumes 1 MET per hour, per kilogram, or 1 cal kg-1h-1 x 8h x 60 kg , which is 480 calories. Now, the government has gone to the trouble of computing METs values for all the categories from the American Time Use Survey and from scanning through the “Working and Work Related” activities, it looks like those not involving heavy physical work ( i.e. management, business and financial, legal, computer and technological ) seem to range in METs from between 1.5 and 2.5 ( see the table below ). We’ll split the difference and say that Kim expends 2 METs for every hour that she’s working, which makes her work caloric expenditure double that of her sleeping rate, or 960 calories! Not bad, but we’re 2/3 of the way through the day, and we’ve only gone through 1440 calories, or about 2/5 of what we need to do.
For her household activities, let’s say that EK engages in rather vigorous ones, which boost her METs to 3.5! This gives her an additional calorie burn of 630, bringing the total to 2070. In terms of socializing and leisure activities, that’s about 2 METs for 3 hours, or 360 calories more. The running total is now at 2430 calories, and EK is about to emabark on her 2 hour exercise regime, one which must consume the remaining 1070 calories, implying a requisite METs for that activity of at least 9 METs. The kinds of activities that Kim needs to engage in for two hours straight range from: vigorous bicycling between 14 – 15.9 mph, climbing hills at walking speed while carrying a 42+ lbs. load, or treading water at a fast vigorous pace.
Extreme Kim’s problems are compounded by her choice to fast for the 10 days which is sure to impact on her ability to engage in 9 METs activities for a solid two hours, especially during the latter half of her diet and exercise program. Nevertheless, if we give her the benefit of the doubt, it is theoretically possible, albeit rather gruelling, that she pull it off. Did we mention that she is doing this daily while fasted? Extreme Kim has well and truly earned her nickname!
Reasonable Kim (RK)
RK would never go so far as to forgo eating. She has consulted with her trainer and nutritionist, and has been advised that she ought to restrict her calories to 1500 daily, maybe allocating 500 calories per breakfast, lunch, and dinner to keep things simple. In all other respects, however, her lifestyle and activities closely parallel Extreme Kim.
RK, however, whether she realizes it or not, has made a decision to trade in an extreme diet for extreme exercise. By eating 1500 calories daily, when it comes to the number of calories she needs to expend in her allotted two hours for exercise, it is the same as EK’s 1070 but with the additional 1500 calories from her meals, for a whopping 2570 calories. As a result, RK needs to engage in a 21 METS activity, for two hours a day, for 10 days straight!
If you consult the compendium of physical activites tracking guide, you would find no activities listed with a 21 METs energy expenditure. The closest would be running at a 5.5 minute mile pace with a MET rating of 18. To put this in perspective, this is equivalent to running a marathon in 02:23:00. This means that Kim would be running at a pace that would have beaten all but 4 of the 45 Boston Marathon Women’s Open winners since 1966. Of the 4 times that Kim would be off the race winning pace, she would never be more than 2.5 seconds behind the winner. Given that Kim would actually be running at a 21 METS pace, not 18, she would have decimated the field in any of the marathons she chose to enter. Oh yes, let’s not forget, she would need to do this 10 days in succession … that is, for 10 days straight, Kim would be running a 3/4 marathon at the race winning pace for the Boston Marathon in 2010.
Did she, or didn’t she?
Assuming that Kim was forthright and didn’t embellish the degree of weight lost during her 10 days, and further, being familiar with the journalistic high standards to which celebrity gossip magazines are held, is it possible and likely that she lost 10 lbs.? Yes, it is. If all we’re concerned with is weight, then the easiest thing to do is to manipulate the amount of water that the body is retaining. Adopt an extremely low carbohydrate diet, and you will quickly shed water weight since every gram of carbohydrate is stored in the body with an associated minimum of 2 grams of water. Some estimates put that figure as high as 4 grams of water. Incidentally, this is why your body stores energy as fat. Fat does not carry with it this extra water ballast, it is essentially a “carbohydrate concentrate!” As soon as you shed the carbohydrates, the water required to keep it soluble is shed as well … voila … instant weight loss. Additionally, if health is not your primary focus, diuretics and laxatives can greatly assist you in this process. This might make you look better in a bikini, but that will instantly reverse itself if you increase the relative amounts of carbs in your diet. Note that you need not change your caloric intake at all, rather merely by increasing the proportion of carbohydrates in your diet you would gain water weight.
On a personal note, about two weeks ago, I gained about 6 lbs. overnight. Given that I track my diet quite closely, and weigh myself upon waking every morning, I was quite certain that a) there had not been any dramatic change in my diet, and b) that I had indeed gone up in weight by about 6 pounds. If this were to be the result of fat accumulation due to overeating, this would represent a caloric surfeit of 21, 000 calories, or, the equivalent of eating 9 kg. of steak. Even if we were to allow for the possibility of eating while sleepwalking, there was not 9 kg. meat in the house to be eaten overnight! The only possible explanation was water weight. As it had been unseasonably warm where I live and knowing that I have seasonal allergies, I expect that I was experiencing a mild bout of edema from a histamine reaction. Not to worry, the following day, I had lost the weight!
All of this should point out the dubious value of the scale as a body recomposition tool. It is a very blunt instrument, and should not be considered the arbiter of anyone’s progress. It is useful mostly because of the very low effort required to use it. However, it should be backed up with more reliable measures, such as skin fold measurements, or simply a tape measure.
Ultimately, if what interests you is fat loss, rather than an arbitrary number on a scale, then you need to realize that there is a practical limit on how much weight can be lost on any given day. Extremely rapid weight loss is not practical or sustainable over the long run. This is not a sprint, it is an endurance race. If anyone tries to tell you otherwise, they are probably selling something.