February 29, 2012

Nutritional Biochemistry

Do calories matter?

Read Time 9 minutes

In a word, yes.  But, technically this is the wrong question.

 The correct question is probably closer to, “What is the impact of the calories I consume on my body’s ability to store fat versus burn fat?

The immediate follow-up question to some variant of this first question is, “Should I be counting calories?” In a word, no. But you’ll want to read this post fully to qualify that answer.

Before I answer these important questions, let’s spend a few moments reviewing five key concepts.

Key concept #1 – the definition of a calorie

A calorie is a unit of measurement for energy content. By formal definition a calorie is the amount of heat energy required to raise one gram of water from 14.5 to 15.5 degrees Celsius at atmospheric pressure.  One-thousand calories is equal to 1 kilocalorie, or 1 kcal for short.    Here’s where it gets a bit tricky.  Most people use the term “kilocalorie” and “calorie” interchangeably.  So when someone says, “a gram of fat has 9 calories,” they actually mean 9 kcals.   The important thing to remember is that a calorie (or kcal) tells you how much energy you get by burning the food.  Literally.  In the “old days” this is how folks figured out the energy content of food using a device called a calorimeter.  In fact, to this day this is how caloric content is measured when doing very precise measurements of food intake for rigorous scientific studies.  As a general rule carbohydrates contain between 3 and 4 kcal per gram; proteins are about the same; fats contain approximately 9 kcal per gram.

[If you’re wondering why fats contain more heat energy than carbohydrates or proteins, it has to do with the number of high energy bonds they contain. Fats are primarily made up of carbon-hydrogen and carbon-carbon bonds, which have the most stored energy.  Carbs and proteins have these bonds also but “dilute” their heat energy with less energy-dense bonds involving oxygen and nitrogen.]


Key concept #2 – thermodynamics primer

It might be a good time, if you haven’t done so recently, to give a quick skim to my previous post, revisit the causality of obesity.  In this post I review, among other things, how the First Law of Thermodynamics explains fat accumulation and loss.  To reiterate, the First Law of Thermodynamics says that the change in energy of a closed system is equal to the energy entering the system less the energy leaving the system.  When we apply this to fat accumulation, it looks like this:


People like me (and others) get a bad rap from folks who lack the patience (or training, perhaps) to actually hear the entire argument through before throwing their hands in the air, waving them frantically, and screaming that we’re violating the First Law of Thermodynamics for asserting the Alternative Hypothesis (more on this below).

Let me be as crystal clear as possible, lest anyone feel the need to accuse me of suggesting the Earth is flat.  The First Law of Thermodynamics is not being violated by anything I am about to explain, including the Alternative Hypothesis.


Key concept #3 – current dogma

Conventional wisdom, perhaps better referred to as Current Dogma, says that you gain weight because you eat more than you expend.  This is almost true!  To be 100% true, it would read: when you gain weight, it is the case that you have necessarily eaten more than you expended.   Do you see the difference? It’s subtle but very important — arguably more important than any other sentence I will write.  The first statement says over-eating caused you to get fat. The second one says if you got fat, you overate, but the possibility remains that another factor led to you to overeat.

If you believe Current Dogma, of course you’ll believe that “calories count” and that counting them (and minimizing them) is the only way to lose weight.

Key concept #4 – the rub

Most folks — but not all — who subscribe to Current Dogma do so, in part, because they don’t appreciate one very important nuance.  In the equation above, explaining the First Law of Thermodynamics, they assume the variables on the right hand of the equal sign are INDEPENDENT variables.

Let me explain the difference between independent and dependent variables for those of you trying to suppress any memories you once had of eigenvectors.  As their names suggest, independent variables can change without affecting each other, while the opposite is true for dependent variables.  A few examples, however, are worth the time to make this easy to understand.

  • The weather and my mood are dependent variables.  When the weather goes from gloomy to sunny my mood tends to improve as a result of it, and vice versa (i.e., when the weather goes from sunny to gloomy, my mood goes from good to bad). In this case the dependence is only one-way, though; my mood changing has no impact on the weather.
  • My countenance and my interaction with people are dependent variables.  When I smile it seems to cause a more positive interaction with the people around me.  Similarly, when I’m having a good interaction with someone I tend to smile more.  In this case the dependence goes both ways.
  • My height (while I was still growing) and my hair length are independent variables.  Both of these variables can change without any impact on each other.

How does this tie into the idea of the First Law? Let’s re-write the First Law with a bit more specificity:

The change in our fat mass is equal to what we eat and drink (the only source of energy entering our system) less all of the energy we expend.


Now let’s be even more specific on the “expend” part of the equation.  We expend energy in four ways: Digestion (all the energy we require to break down food, plus the undigested portions that leave our body); Exercise (everyone knows what this is, but I tend to separate it from daily activity since people really like to focus on exercise); Daily activity (the non-exercise activity we carry out); Basal expenditure (the energy we expend “underlying” any activity – e.g., when you are resting).

Let me clarify something before going further.  There are several ways to enumerate and account for our energy expenditure. I happen to do it this way, but you can do it other ways.  The important thing is to make sure that you are collectively exhaustive when doing so (and mutually exclusive if you want to make your life easier – we call this MECE, pronounced “mee-see”).

The First Law is only valid when you consider ALL of the energy entering and leaving the system (i.e., your body).


Back to the independence versus dependence issue for a moment.  If you look at the equation above, and believe the red box has no impact on the green box, and vice versa, you are saying that energy input and energy expenditure are independent variables.  However, this is not the case, and that is exactly why this problem of energy balance is so vexing.  In fact, the figure below is a more accurate representation of what is actually going on (and even this is a gross oversimplification for reasons I will mention shortly).


What you eat actually changes how you expend energy.  Similarly, how you expend energy changes what (and how) you eat.  To be even more nuanced, what you eat further impacts what you subsequently eat.  As you increase (or decrease) in size, this impacts how you expend energy.

So there are actually a whole bunch of arrows all over this diagram (I’ve only shown 2: what you eat impacting how you expend, and vice versa. If I included all of the arrows, the diagram would get out of control pretty quickly).

I’m not telling you anything you don’t already know, even though it may sound like it for a moment.  When you exercise your appetite rises relative to when you don’t exercise.  When you eat a high carb meal you are more likely to eat again sooner compared to when you eat a high fat/protein meal due to less satiety.


Key concept #5 – the Alternative Hypothesis

If, like me, you don’t subscribe to Current Dogma, you’d better at least have an alternative hypothesis for how the world works.  Here it is:

Obesity is a growth disorder just like any other growth disorder.  Specifically, obesity is a disorder of excess fat accumulation.  Fat accumulation is determined not by the balance of calories consumed and expended but by the effect of specific nutrients on the hormonal regulation of fat metabolism.  Obesity is a condition where the body prioritizes the storage of fat rather than the utilization of fat.

Why is this different from Current DogmaCurrent Dogma says it doesn’t matter what you eat, it only matters how many calories that food contains.  If you eat more calories than you expend, you gain weight.  The last part is true, but the first part is not. The Alternative Hypothesis says it DOES matter what you eat and for reasons far beyond the stored heat energy in the food (i.e., the number of calories).

Let me use an example to illustrate this.  Consider the following table of various substances known to contain a lot of stored energy.  The table shows their energy content in units we usually use to describe energy density, kilojoules per gram (middle column), and I’ve converted to units we typically only use for food energy, kcal/g or “calories” per gram, (right column). [Here we need to be very clear to distinguish between a technical calorie and a kilocalorie, which is almost always what we mean.]  A kilojoule is about 240 calories (not kilocal), so 1 kj is about 0.24 kcal, and therefore 1 kj/g is about 0.24 kcal/g.

I’ve highlighted, in bold, four rows of things we typically eat: fat (olive oil, to be specific) with about 8.9 kcal/g; ethanol with about 7.0 kcal/g; starch with about 4.1 kcal/g; and protein with about 4.0 kcal/g.

I’ve also included in this table some other substances known to contain chemical energy such as liquid fuels (e.g., gasoline, diesel, jet fuel), coal, and gunpowder.  Hard to imagine a world without these chemicals, for sure.

A quick glance of the table, which I’ve ordered from top to bottom in terms of caloric density, would suggest eating olive oil would be more “fattening” than eating starch since it contains more calories per gram, assuming you subscribe to Current Dogma.

But that same logic would also suggest eating coal would be more fattening than starch and gunpowder less fattening than ethanol.   Gasoline would be more fattening than jet fuel.  Hmmmm.  Anyone interested in testing this hypothesis (personally)?  Despite my wildest self-experiments, this is one self-experiment I’ll pass on.  Why?  Well for the same reason you’d pass on it – you know that there are far more important consequences to drinking diesel or snorting gunpowder than their relative energy densities.


Sure, everything on this list is an organic molecule largely composed of the following four atoms: carbon, hydrogen, oxygen, and nitrogen.  Not to bore everyone with a lesson on organic chemistry, but it’s the actual bonds between these atoms that are responsible for their energy densities.  When you “liberate” (i.e., break) the bond between an atom of carbon and hydrogen, for example, you release an enormous amount of stored chemical energy.  This table tells you exactly how much energy you would release if you were to break the bonds in these molecules, but that’s all it tells you.  You can’t actually know, just by looking at this table, if jet fuel is more paraffinic than diesel or if gasoline has more isomerization than propane.  And, you certainly have no idea, from the information contained in this table, of exactly how each of these substances will impact the hormones, enzymes, and cell membranes in your body if you ingest them.

Is it relevant to our bodies that olive oil has about the same energy density (i.e., calories) as biodiesel (also known as fatty-acid methyl-ester)?  Or, is it more relevant to us that consuming olive oil has a very different effect on our bodies than consuming biodiesel beyond anything to do with the calories contained within them?  Obviously consuming equal caloric amounts of olive oil versus biodiesel will have a very different impact on our body.  Why then is it so hard to appreciate or accept that equal caloric values of olive oil and rice could also have very different impacts on our body?

The upshot

Let’s get back to the question you actually want to know the answer to.  Do calories “matter”, and should you be counting them?

Energy density (calories) of food does matter, for sure, but what matters much more is what that food does in and to our bodies.  Will the calories we consume create an environment in our bodies where we want to consume more energy than we expend?  Will the calories we consume create an environment in which our bodies prefer to store excess nutrients as fat rather than mobilize fat?  These are the choices we make every time we put something in our mouth.

Our bodies are complex and dynamic systems with more feedback loops than even the most elaborate Tianhe-1A computer.  This means that two people can eat the exact same things and do the exact same amount of exercise and yet store different amounts of fat.  Does it mean they have violated the First Law of Thermodynamics?  Of course not.

Similarly, genetically identical twins can eat different macronutrient diets (i.e., differing amounts of fat, protein, carbohydrates) of the same number of calories, while doing a constant amount of exercise, and accumulate different amounts of fat.  Does this violate the First Law of Thermodynamics?  Nope.

What you eat (along with other factors, like your genetic makeup, of course) impacts how your body partitions and stores fat.  In case anyone is wondering how I got over 2,000 words into this post without mentioning the i-word, wonder no longer.  Insulin, while not the only factor involved in this process, is probably at the top of the list. When you eat foods that have the double whammy of increasing insulin levels AND increasing your cell’s resistance to insulin, your body prioritizes fat storage over fat utilization.  No one disputes that insulin is the most singularly important hormone for causing fat cells to accumulate fat.  Somehow the dispute centers on what causes people (full of billions of fat cells) to accumulate fat.

All calories are not created equally:  The energy content of food (calories) matters, but it is less important than the metabolic effect of food on our body.

Photo by Aaron Barnaby on Unsplash

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  1. Peter, thanks for the straight, clear presentation once again. I’ve started the keto journey once again following your blog. Keep up the good work.

    • Dr. Attia and forum members:

      I’m 41 male and have about 30 lbs of fat to lose. Blood glucose testing all my life had always been around 85 through fat and thin.

      Went low carb/no sugar a couple of months ago and have lost 6 or 7 lbs so it’s working and I feel great.

      Had a blood draw after 12 hour fast the other day and BG was 125. Actually felt a little lightheaded during the draw, which was a first for me ever giving blood.

      Not really alarmed (yet) but just curious what’s happening with the 125 level. Is this the fat stores releasing into my blood from going primal and making the reading high? Is it less insulin in my blood? Since I was feeling a little woozy, did my muscles/liver/fat dump emergency extra glucose into my blood and spike the readings?

      Other notes:
      Triglycerides are coming down since then (from 200 to 115)
      HDL going up (from 40 to 53)

      I should mention my daily carbs hover around 75g.

      Thanks for any insight.

  2. Great write Dr Peter!

    Any thoughts of signaling of food choices. More specifically, I feel better/leaner when I up my fat intake. Do you think your body is more prone to release fat-stores as if you are signaling to your body that food is plentiful no reason to store it. Hopefully you understand what I am getting at. ie…bears hibernate and what way they store more fat is by upping there intake of fruit and tubers…since fish become less plentiful in the fall.

    Thanks again for the great analysis!

  3. Another amazingly comprehensive post, Peter!

    Beyond the actual science, I prefer to sum it up very simply to those I encounter about this subject:

    It’s a LOT harder to expend more than you consume when you’re ingesting foods that just tempt you to eat more (and store more fat!) Sure, you can do it for a little while – but I’d like to see how sustainable the “feeling of constant hunger” is for you!

    So it really was a fantastic revelation for me last year to realize that the types of food I ate – actually helped me eat less and expend more.

    Thanks again.

  4. Excellent post.

    Re your comment: “All calories are not created equally: The energy content of food (calories) matters, but it is less important than the metabolic effect of food on our body.”

    I think this is true both for weight maintenance and health maintenance. I do better metabolically, mentally and emotionally when I avoid foods that spike my blood sugar and insulin.

    Changing to a low carb, real food diet has exponentially increased the quality of my well being and physical health, and this, I think, is another important point to remember about food quality.

  5. Another intelligent and well-written post. As a biomedical student, I find it interesting that my current educators don’t go into this sort of detail; indeed seem desperate to cling to conventional wisdom. In my last year’s organic chemistry class, the professor did not explain any significant impact on the body when saturated fats are eaten in conjuction with refined carbohydrates, only that eating saturated fats will cause you to keel over from heart disease and artheroslcerosis! When I questioned him about this, as I had been reading paleo related websites, he simply reiterated the alleged “conventional wisdom”, which does not actually appear neither conventional nor wise, as we are getting fatter and fatter! Also, cheers for keeping your website being free and non- preachy.

    • Renee, I’m glad you’ve got the courage to ask hard questions, even when they go against conventional wisdom (which once told us the Earth was flat).

      • So the Alternative Hypothesis has made no impact whatsoever on the medical establishment, obesity research community, etc? Have Low Fat proponent offered any serious response? Taubes’s book has been out for quite a while and his work must be known to all who seriously research the obesity epidemic.

        • Correct, the AH has not made much of a dent in the thinking of the medical establishment. Part of the problem is the same problem faced by Galileo and other who were ahead of their time — it takes time to turn a tanker ship. Fret not, though. NuSI is going to make this more explicit. Either we at least test the AH, or we continue down the path we’re on. Which makes more sense?

  6. Thank you for the explanation.

    I’ve been eating low carb, and according to ketone test strips I have been in ketosis for several weeks. I eat according to my appetite, but my weight has not dropped in two weeks.

    Is it common to plateau like this? I’d rather not start counting calories.

  7. Great and timely article.

    I’ve been going strong on the low carb lifestyle for nearly 3 weeks now, and it’s not nearly as emotionally taxing as I thought would be. In fact, I’m enjoying it!

    However, where some important questions are now showing up are in the areas of minimum caloric requirements (and minimum protein requirements) for the body.

    Some prominent authors argue in favor of strict calorie counting not simply to warn against the effects of overeating/excessive energy in but also to discuss the effects of underconsumption/inadequate energy in. The authors suggest that there will be the following:

    1) some minimum number of calories required before the body reacts to *perceived* starvation by (among other things) slowing down the metabolism anywhere up to approximately 40% of normal function and

    2) some minimum amount of protein consumed to prevent the body from catabolizing muscle tissue AND that there is no way to prevent your body from catabolizing important organ muscle tissue rather than, say, the quadricep muscles.

    This concept, of course, is rather disconcerting and frustrating as it gets back to the suggestion (for *healthy* weight loss) for creating a energy deficit within a range, which, as Taubes put it (or at least alluded to), is not really at all possible the do accurately with current technology. One can certainly have your meals created precisely enough in a laboratory with very specific numbers of calories and macro/micronutrients, but how would one ensure he/she expends only so much energy as to remain in the narrow range of energy deficit?

    So, my two questions are:

    1. Do you agree that there might be some minimum required total calories to prevent the metabolism from significant slowing?

    2. Do you agree that there might be some minimum required total protein consumption to prevent muscle (and especially organ muscle) catabolism?

    Many thanks, Dr.


    • Anthony, thanks for your comments. Yes, there is certainly a minimum amount of caloric intake our body needs below which we can’t maintain weight. The problem, when one uses the “starvation” method to lose weight, is that you lose both lean and fat tissue (and it’s hard to gain back the lean tissue while calorie deprived), and your body compensates for the deficit buy trying to slow overall expenditure.
      Here is my take: eat when hungry and stop when not. Assuming you don’t take medication that suppress your appetite I trust that your body is smart enough to get it right. As far as protein, depending on your demands, somewhere between 1 and 2 gm/kg/day is sufficient, so make sure you’re in that ballpark.

      • Thank you so much. It is truly incredible that you respond to the massive number of questions with such well-thought answers.

        Kind regards,

      • It’s also been my recent understanding that if there is an underlying hormonal reason for the fat deposition, a starvation diet will likely result in a person who weighs less and retains more body fat than a typical lean person (that didn’t get lean via a starvation diet).

        I recall Gary Taubes talked about both the human and animal evidence indicating such a phenomenon. The implication seems to be that the typical obese person would lose more lean mass under an unsustainable starvation diet and when they inevitably resume their old lifestyle, the hormonal dysfunction persists or is now even worse.

        I would also assume that people with functional and dysfunctional hormonal metabolisms would probably respond differently to moderate or even severe restriction.

  8. Best. Post. Ever!
    Peter, so great to see that you have a blog, and I just can’t wait to say to one of my “calories count” friends, “Then I have a diet for you, ‘the gunpowder diet’…or would you be willing to entertain the notion that what you eat has effects on you beyond merely the calorie content of said food item?”

  9. I’m interested in the exercise component of this as well as the dietary component. A couple of summers ago we rode our bikes from Toronto to Montreal, about 700 km; I weighed myself before the trip and after, and lost only one pound despite expending thousands more calories than I took in. In the weeks that followed, however, I lost 10 pounds while eating like a horse and getting virtually no exercise at all (I wasn’t eager to get back on the bike for a while). While the trip undoubtedly built up my leg muscles, my understanding is that the caloric benefits of muscle gain wouldn’t be significant enough to account for anywhere near that kind of weight loss over a few weeks. The feeling I had was that my body had shifted into a kind of weight-loss mode, and I would keep losing weight regardless of what I ate or whether my daily intake exceeded my daily burn rate. I experience a similar phenomenon in reverse when I do start to watch my diet and/or calories: I get the feeling that my body remains stuck in “weight gain” mode for a while and my actions have little effect, but then there’s a shift and I lose weight even if I happen to overeat for a few days. I definitely feel a lag effect between my actions and changes on the scale.

    • Brad, excellent observation. I think about this question A LOT and plan to write about it. In fact, next week’s post will touch a little on this. At the end of the ride, despite a MASSIVE caloric deficit you had effectively lost no overall weight. Why? I highly suspect that you had lost fat mass, but your BODY mass stayed constant due to water retention through a profoundly vigorous inflammatory response due to the stress of the ride. In the coming days, as the inflammation subsided the “third spacing” of fluids (that’s ICU talk for what happens when your body retains fluid due to an inflammatory response), you probably urinated more than usual (though I imagine you don’t recall this now), and your weight started to reflect the new equilibrium. These effects tend to be transient, though. There are probably other factors involved, also, such a short-term change in your insulin sensitivity. I’ll do some writing about this in the near future, I hope.

      • Peter, As usual, thanks so much for the great post. I can’t believe this information is for free…

        Mark Sisson has pointed out the negative effects of over-traing calling it “chronic cardio”. Had you planned on doing a related post on this – overtraining and its effect on inflammation…furthermore inflammation’s effect on insulin sensitivity? (Would that be a logical cause and effect?)

        • Sorry Peter, I had missed the part about you planning on doing more writing on the subject. I assume that it will involve the idea of “chronic cardio” and over-training.

        • Thanks so much, Michele. Training, period, leads to inflammation – so the question is how much inflammation should one tolerate (some inflammation is a very good thing; no inflammation equates to death)? I will write about this.

        • I look forward to this post. I’m planning a long distance bike trip for this summer. I’ll probably be riding 5-10 hours per day. Some nutrition guidance would be appreciated. All the conventional wisdom says I should be eating carbs continually throughout the ride. Also if I don’t eat a ton a will “hit the wall” and be unable to perform. You seem like you’ve had some experience with endurance events. I look forward to any eating tips you might have.

      • Peter, I am looking forward to this future post on inflammation. I’ve been no-starch, no-grains for about 3 months now and I’ve absolutely slimmed down significantly but my weight is barely budging, maybe 2-3 lbs at most. It is mind-boggling. And in my online research, the best thing I can find is that maybe my body has replaced the fat with water as kind of a “place-holder” in the cells because it “doesn’t want to” get rid of the weight. I’m not exactly sure what this means, but I can’t find any better/other explanation. I have upped my running speed and distance somewhat and run 3-4x/week, so maybe inflammation is causing the water retention. Hopefully you can incorporate some explanation of this common “losing inches, not lbs” issue lots of low-carbers seem to experience. Thanks so much for your great posts!

        • Yes, Erica, I see this quite a bit – more so in women than men. It know it’s frustrating for people. This is one of the advantages of using DEXA scans to actually measure body composition, which is why I highly recommend them.

      • Peter, you wrote, “I highly suspect that you had lost fat mass, but your BODY mass stayed constant due to water retention”.

        Despite my excellent effort at eating a high-fat, modest-protein, and very low-carb diet, after the first couple weeks, my weight loss stalled for almost a month… no, stopped, in fact.

        I reduced my use of cream, stevia, and tried to even eat less (didn’t work) to figure out what is wrong. Why am I not losing weight. But when I read the above, it really makes me wonder if I should toss out the scale (because the fat loss is working, but hidden by water), or did my ketosis just “conk out”?

        I no longer know what to believe, or if anything is really occurring, as like most people, I rely on both the scale and my belt notches to give me confirmation that I am losing weight, yet for almost a month, they have not changed, so I am left to believe I am not in ketosis, but don’t know why.

  10. Thank you for this post! For the sake of drawing this out, and even though everyone’s metabolisms are a bit different, could you address this theoretical question:

    Let’s say someone is really minimizing their carb intake (even to zero) and keeps protein under control. Their insulin levels are as low as they possibly can be. They sit down and force themselves to eat many, many calories worth of fat. Let’s even say that over the course of a few days, they manage to eat, say, 17,500 calories of fat. Even if their appetite is low and they are “forcing” it down. Given that insulin is bottomed out, will they gain weight from this caloric overload?

    Maybe a simpler way of asking this is, if someone has minimized their insulin levels and they eat what would appear to be excess calories in the form of fat, will they gain or will their body find a way to waste the excess energy? At least theoretically.

    Thanks! 🙂

    • Great question. ASSUMING they can physically eat that amount of food without immediately re-expending (i.e., vomiting), they almost certainly WILL gain weight. It probably would not be as much as predicted by just the number of calories it (e.g., a lot of fat would exit in the stool), but in the end the First Law never lies. The energy needs to be accounted for somehow.

      • Peter, thanks for your answer. On a related question, would you mind addressing your experiences with caloric expenditure on a very low carb diet?

        You personally eat more calories than you used to, and you have LOST weight without increasing exercise. Yet Eades on his Protein Power blog (see https://www.proteinpower.com/drmike/weight-loss/low-carb-and-calories-2/) suggests that people who want to lose weight still need to try to limit calories in order to lose, though when they reach their goal weight, they can then up calories again without gaining.

        What is your experience with yourself and others? Let’s say that someone’s typical caloric requirement is about 2,200 calories a day, and she eats that mostly through fat with adequate protein and under 15g net carbs. Could she expect to lose (albeit slowly) since insulin is under control, or does one really need to cut calories until goal weight is reached? How varied are peoples’ responses? There seems to be a lot of confusion and disagreement about this among the low-carb advisers.

        Personally, even if my carbs stay very low, I get hungry if I try to cut calories below 1900 or so.

        Thanks again! I look forward to your posts each Wednesday!

        • It’s so variable. In my experience, about a quarter to a third of folks who greatly reduce carbs (like me) actually eat much more in overall calories, but still lose weight. About a third do a eucaloric swap (i.e., eat about the same number of calories), about a third eat fewer total calories. I wish I knew WHY this happened, but I don’t.

    • Peter, depending on the macronutrient content of the diet, the storage of excess calories may not be possible.
      Let me know your opinion on the hypothetical scenario depicted below.

      First, some undisputed textbook biochemical concepts:

      1. The non-ketotic body needs 160 grams of carbohydrates each day: 120 grams for oxidation by the brain and 40 grams for the glycolitic tissues.
      2. In the ketotic state, the ketones can supply the brain with up to 50% of its energy expenditure .
      3. The minimal protein intake for a physically active individual would be 1 gram/kg of body weight.
      4. The molecular weight of a typical triglyceride molecule is about 850. That of glycerol is 90, which means 10% of the weight of a triglyceride molecule is glycerol.
      5. Our body cannot make glucose, nor any intermediate which ultimately leads to glucose, from fatty acids, at least not in a net sense.

      Now consider a sedentary 70 kg (154 lbs) woman. She`ll be put on a 3-day/week weightlifting program, and will be fed a diet consisting of 3960 calories/day (400 grams Fat, 70 grams Protein and 20 Grams Carbohydrate). A reasonable estimate of the total energy expenditure of a 70 kg woman would be 2700 Kcal/day on training days and 2300 Kcal on resting days. If she’ll be eating 3920 Kcal/day, that would amount to more than 1200 excess calories each day (36.000 Kcal/month). She should gain a lot of weight in the long run. Right? Let’s take a closer look.
      She’ll be eating 20 grams of carb per day, plus 40 grams of glycerol from the fat (remember, glycerol is 10% of the weight of the triglyceride molecule). That’s all the carbons (60 grams) that will be available for the production of new glucose each day, since the protein intake is exactly the amount to supply the minimum daily requirement (1 gram/kg of bodyweight). All these glucose carbons will be used for oxidation by the brain, in a net sense. The other half of the brain energetic requirement will be supplied by ketones. But, we’ll have at least 1200 Kcal/day that will have to be stored, since they will be in excess of the total energy expenditure. The fat in our body reserves is always in the form of triglycerides. The excess fat calories will have to be stored, but the fatty acids will be then, we could say, orphans, since their glycerol moiety would have been used for gluconeogenesis. There’s no way for them to be stored, unless the body uses its structural or functional protein pool to generate glucose in the liver and than glycerol in the fat cell. But if that happens, we would have a ridiculous situation, in which a sedentary 70 kg person starting a weightlifting program and eating 3920 Kcal/day would get weaker since day 1 and would eventually die of protein malnutrition, as her body would eventually use a great portion of its body protein to produce glycerol, in order to store the excess ingested calories. In the long run, the wasting of protein would become increasingly larger, since the loss of lean tissue would lower the total energy expenditure, making the amount of excess ingested calories progressively bigger. By all we know about how fiercely the body protects ist protein pool, and from practical experience, we can dismiss the above outcome as nothing but impossible.
      So what will the body do with the excess calories? It will have to burn them, and by doing so it will raise its total energy expenditure. It’s simple as that.
      In other words:
      The woman would ingest 400 grams of fat, 20 grams of carbs and 70 grams of protein each day, and approximately 133 grams of that fat would be in excess of the expenditure, and would have to be stored. But the glycerol of the fat would have been divert to the gluconeogenic pathway, and there would be no other source of carbons for glyceroneonesis besides those from the protein pool, which the body fiercely defends, and from the ingested protein, which matches exactly the amount necessary for the protein turnover.

      So we have two competing scenarios:

      1. The woman dying of protein malnutrition, despite eating 3920 Kcal/day and 1 gram/kg of bodyweight of protein. By this reasoning, if she ate less fat and less calories, she would do fine (maybe would even gain some muscle).
      2. The woman simply burning the excess calories, and not gaining a single pound of fat.

      Put that way it looks overwhelming obvious that she wouldn’t gain fat weight, perhaps because of the sheer absurdity of scenario 1. This is all common biochemical knowledge has been available for decades, and is not even disputed.
      I’d like to hear opinions on that.

      • So my intuition when I first read this was that you were over-estimating the shortage of glycerol and under-estimating the ability for re-esterification to take place. I ran the scenario you posed by Kevin Hall at NIDDK who has a robust model (it’s available on line). Model confirmed my hunch. There is no shortage of glycerol since GNG goes up and carbohydrate oxidation becomes suppressed thereby allowing enough glucose to be available for glycerol production to support the increased TG synthesis and a net positive fat balance along with positive protein balance.
        Nevertheless, a very nice thought experiment, Humberto.

    • Hi Peter .. please can you explain the ‘fat being exited in the stool’ component above. My understanding is that the gut can absorb x amt of fat at a time. If what is absorbed is excessive and cannot be used, it ends up being stored in fat cells. Explanations that I have seen state that by eating fat more often, your gut has the opportunity to absorb more fat – meaning that x amount of fat consumed over 5 meals will allow for the absorption of more fat than what could be absorbed if consumed in 1 meal.

  11. I’d be interested to hear if you have done any in-depth research into the role of UCPs when evaluating basal expenditure. I seem to recall that putting rats on ketogenic diets causes them to emit ~15% more heat, and I was wondering if you’ve observed similar results in humans. I certainly like the idea of up-regulating UCPs so that my basal metabolism can skyrocket.

    • Scott, this information is pretty hard to come by in HUMANS with GOOD studies, because they require very rigorously controlled trials. I don’t put much faith in rat or mouse studies, even though they certainly suggest things (rats are, of course, better than mice as mice are herbivores). NuSI will be funding this exact kind of work, so please stay tuned.

  12. Hi Peter,
    What about for someone that has the opposite problem: I can’t seem to get past 170lbs despite a regimen of heavy weights and lots of protein/carbs. I’m 31, 5’9. Do I need to worry about carbs so much if I’m not really concerned about weight/fat gain? I thought it was about calories In, so I ate a lot of junk food and stuff trying to gain mass.

    I guess my point is….for someone that isn’t really concerned about fat gain, do we need to worry about our carb intake? I had a blood test done 2 weeks ago and my LDL-P is 367 (I take 2000mg of fish oil/day and a 5mg statin every few days).

    • Nick, take this is kindest way possible, but you’re a freak! You lucky guy! You “suffer” the same problem as my wife. You are are clearly on the far side of the carbohydrate sensitivity spectrum as demonstrated by these numbers. That LDL-P is in the bottom 1%. As one reader pointed out a few weeks ago, one drawback, perhaps, of being profoundly carb resistant (as you are) is that you may have a harder time with anabolic demands. In other words, the same thing that “protects” you from gaining fat, my inhibit you from gaining muscle. Doesn’t mean it can’t be done, of course, it’s just harder. With the right diet, the right timing of meals, and the right training, you can make gains.

  13. Fantastic post! I’ve been trying to find a way to explain this idea to people who are resistant to it, and I don’t think I could’ve come up with something so easy to grasp. I don’t know why it’s so hard for people to accept that different foods are processed differently by the body, but from now on I’ll be linking them here so they can get their minds right. Thanks so much!

  14. Peter,

    Excellent post!

    The first version of your equation deals with change in “fat” mass. Should that be “body” mass? We can surely increase lean mass independent of fat mass, no?

    Second, do I take it that your list of energy expenditure also includes waste production? I’m thinking about not only about the obvious heat dissipation but also solid-waste elimination.


    • Patrick, yes, absolutely, to completely correct it would be a change in body mass. In a child, for example, this is much more important as they are gaining weight through increased bone, organ, muscle, and fat gain. However, for the point I am trying to make here (i.e., for the “average” adult), a delta in fat mass is sufficient. But thank you for pointing this out. Yes, the “energy out” includes waste, particularly stool. This is relatively easy to measure, assuming one is willing to collect it.

  15. Peter: First, thank you so much for this very informative website and all your efforts. I discovered you and Taubes about a month ago and it has been an eyeopener to say the least. Since then, at our house we have cut way back on sugar and refined carbs and increased our fat intake. (I knew sugar was added to a lot of foods but it was a shock to see how much is in a piece of whole wheat bread). My personal experience confirms what you are addressing in the post. Almost immediately I noticed I no longer craved a “treat” at night. Some days I am not hungry at all after breakfast and lunch. Any thoughts on whether one should eat some minimum number of calories per day even if not particularly hungry? I look forward to your posts and again thanks for the excellent website.

    • Colleen, so great to hear about your evolving eating habits. I have not (yet) met someone who used hunger as their guide for eating eat too few calories (provided they were not on appetite suppressing medication). Certainly, one can eat too little for basic anabolic and cellular function, but this just doesn’t seem to be a problem for folks who eat when they are hungry and stop when they are not, PROVIDED THEY EAT THE RIGHT FOODS!

      • Peter, I’d like to add here that when in ketosis, I don’t think one has to worry about eating a minimum number of calories each day, provided, you have enough body fat.

        Once the body knows to go to your fat stores as and when it needs energy, everything changes.

  16. Great post and thanks for sharing some more information. The only part I do understand from this “Alternative Hypothesis” is what do people eat after a hard workout? I am a runner and I also mix in weights (Crossfit style), so I never know what I am suppose to drink/eat after a hard workout.

    Any assistance/ideas anyone can offer, would be great. I am a person who has struggled for many years to get his BF% down even after losing 170 lbs. The BF% is still around 28% and I think this way of eating will drive it down, but after workouts I have been “taught” to eat/drink carbs so the protein feeds the muscles, but I have yet to gain muscle or burn fat. So if I follow low carb eating style, how does my body recover from the runs?

    • Fred, this is complex question because it depends so heavily on HOW LOW carb you. Why? If you’re in ketosis like me, you do need to worry about immediately refilling glycogen stores. After long workouts I typically don’t eat much, because ketones are so high and I’m not hungry. But if you are NOT ketotic (which most people are not) do you want to get glucose and fructose in your system as soon as the workout is done. Fructose actually gets assimilated into hepatic glycogen even faster than glucose BUT the doses need to be controlled, so don’t overdo it like most people!

      • Thanks Peter! Well I have tried being in ketosis and you are right, I am not as “hungry” after a workout, but I have always “forced” myself to eat to make sure I “fed” my muscles and to recover. Are you saying that if you are not hungry, you should not eat and it won’t effect muscle development, fat burning or recovery? When I have not been in ketosis, I usually will add a banana to my protein drink. This whole post workout thing is what has had me confused in going all out to ketosis or not. Then when I am not, I feel like my day is ruined by eating some fruit after a workout.

        • Well, it’s a bit complex. I’ll try to write about this in the (near) future. I am very particular about what I eat and when I eat it, when it comes to my training, so while I do let hunger be my guide, I am very thoughtful about how and when I supplement.

        • Fred,

          From my experience I can say a few things. Mind you, it’s an n=1 case. Like you and listened to what everyone says for years and saw no real muscle gain. Definition, yes, but that was it.

          1. Eating after working out?

          It makes no difference to me in as far as muscle build up is concerned. Intensity of your work out is what builds muscle.

          2. Eating Protein, or protein shakes etc. after working out?

          I do none of these and have been gaining muscle mass regularly.

          3. Must eat x grams of proteins each day (typically, based on body weight) or you’ll loose muscle mass?

          I don’t eat anywhere near the amount of protein I “should” be eating and yet I gain muscle mass.

          As far a gaining muscle mass is concerned, there is (I think) only one way to do it. Increase the intensity. The intensity is such that you are in agony (fight or flight) while trying to complete the last 3 repetitions. I mean real agony. Your body shakes, you’re groaning out loud or you’re screaming and you break out in a sweat even in the cold of winter. That kind of intensity. Such intensity that even in a matter of life and death you won’t be able to do yet another repetition.

          You do that and you’ll find your muscles responding daily.

          Stop all the shakes and “carbing up” stuff.

      • I had the same question because of moving into ketosis and then back out when I added some raw honey and fruit to help me get over a cold faster the last few days. This answer helps, I guess I’ll eat a few more carbs the day before the race and some fruit after and then try to get back to ketosis before my next race. 🙂

  17. I think the comparison of biodiesel to olive oil brought a whole new level of clarity to this line of argument. Thanks for that.

  18. Peter, I look forward to your bog every week, and this is another good post. I have a related concern that maybe you could shed a little light on. Is it possible for a person on a low-carb diet, say <50g/day, to still overeat and put on weight? I assume this is less likely than a high-carb diet, but I also would think it is possible. I don't want to cloud your post here, but have you seen this, and what might be causing it?

      • I agree with this, I have been experimenting with my Fat-Protein-Carb balance in the last week and found that if I increase my protein and fat levels to above my current targets, in one case I doubled them, I absolutely put on weight. Even keeping my protein to less than 120g per day. If I maintain my balance at Fat – 80%, Protein – 15% and Carbs – 5% where Fat gram target is 200g per day, then I will definitely lose weight, typically this is 1lb per day, but on occasions it is 2lbs. Also at the moment I am trying to get my nutrition right before beginning any form of exercise as I won’t to make sure that my eating balance is right before being able to blame the exercise for the weight loss. 🙂

  19. “If you eat more calories than you expend, you gain weight.” — Do you and Gary differ in your opinions on exercise? I have heard him say that exercise doesn’t do a darn thing for weight loss. I understand that the kinds of foods we eat matter more than a simple calories in/out equation. But if a person were eating low carb-medium protein- high fat for a couple of months and didn’t see any change in weight or inches, would you expect that an increase in exercise would cause a change in weight?

    Thank you for another informative post. I so appreciate what you’re doing.

    • Malanie, it’s a very complex issue and not one I think any of us FULLY understand. In general (i.e., for MOST people doing MOST types of exercise), exercise per se does NOT seem to lend itself to sustained weight loss, as I discuss this post. However, people who exercise are often more careful about what they eat, and this confounding factor can create a bit of confusion around the process. In controlled studies, though, it’s not clear exercise plays a meaningful role in weight loss. To your second question, it is possible, and certainly worthy of the self-experiment for someone at that plateau. I read a paper yesterday, actually, that showed IN NORMAL HEALTHY YOUNG MALES that high intensity training and an impact on insulin sensitivity. Not clear if this applies more broadly, though.

      • Peter,

        I believe the exercise question as it relates to the insulin mechanism (among many mechanisms) is a complex one that we are only beginning to understand.

        On on hand it is accurate to critique exercise for how it is “sold” in the popular dogma, or as part of a calories-in, calories out equation. In other words, burning calories through exercise is trivial to say the least. What is important, as research is starting to bear out, is the longer term impact of exercise at the cellular level, to include the mechanisms related to insulin. In other words, exercise seems to increase insulin sensitivity, or stave off the negative effects of cells bathed in too much insulin over time.

        That said, carbs can easily overwhelm the capacity of exercise and its positive attributes. As has been said more than once “I’m running 6 miles a day but eating 10 miles a day” which in other words really means eating 10 miles of carbs–easy to do based on the old dogma of feeding endurance sports with a carbohydrate rich diet.

        To be honest, I agree with Gary Taubes on all aspects of his work, but I find him too dismissive of exercise. I believe a close reading of his work reveals this to be a need to expose the fallacy of the calories in/calories out calculus inherent to the pro-exercise ideology. Interestingly enough, within Lustig’s famous sugar video, the Dr. indicates that exercise in fact is quite important for various complex metabolic reasons of which he doesn’t go into during the video (as that’s not the focus). I tend to agree him–that exercise is important, but definitely not for any thermodynamic reasons.

        Great blog!

      • As someone maintaining a large weight loss for many years, I do believe exercise plays a role. While I am a low-carb diet believer, looking at the obesity problem from a chemical perspective only is a mistake. I think it’s important that people understand that on some level they have to deal with the behavioral aspects of overeating – for lack of a better word. Most of us are fairly addicted to delicious – carb – food, and this is why we break any diet, even the marvelous low-carb. In other words, there isn’t a magic pill; we still have to probably weather discomfort at times, maybe even a lot of discomfort. I think it sets people up for failure if they expect the low-carb diet to be painless. There’s nothing wrong with admitting to a little grief at the loss of those favorite food items that were killing us.

      • I think it is common knowledge by now that exercise doesn’t burn many calories directly. I think this depresses people because they think that this means that exercise is useless. No so!!

        Without going into ridiculous detail, exercise does several things:

        There is an immediate non-insulin dependent glucose uptake during and immediately after exercise. This makes sense as there is no way any animal has the luxury of waiting around a few seconds for some sort of unstimulated insulin surge to kick in and deliver glucose to the muscles.

        Just after exercise there is upregulation of insulin receptors on muscle cells thereby increasing their glucose uptake even further. Additionally, the muscles are constantly metabolizing fatty acids.

        (Sorry, I’m getting ahead of myself).

        The decreased blood sugar increases glucagon and growth hormone which incites the liver to create glucose. None of this is unknown.

        The problem is people never discuss the sub cellular and organismal structural changes which accompany exercise when they dismiss exercise as useless.

        There are changes in every aspect of every cell in the body when you exercise and ESPECIALLY when you exercise habitually. Examples include: Hemoglobin synthesis is increased and there is an increased number of erythrocytes. All muscle cells increase mitochondrial density and cell hypertrophy. There is increased vascularity etc. Ligaments and tendons strengthen. Bones increase in density not only due to mineralization but due to collagen formation. The digestive system improves. There is improved sympathetic vascular tone. etc etc etc

        All of the nutrients required for these processes are removed from the fat building and maintenance equation. You convert to a different type of organism, literally.

        This isn’t to say that diet cannot sabotage the entire thing, obviously. Diet is still the most important factor by far. But I think it is unfortunate for people to look a the 150 kcal they burned off in a run and think that’s the end of it. It isn’t. It’s just the beginning.

      • Peter,

        I believe in Dr. Stephen Phinney’s book they cited a couple of studies where groups who exercised lost more weight than groups who did not even thou both groups eat the same food and same amount.

    • The intensity of exercise determines the effects. In my experience, low intensity long duration exercise (“cardio”) has very little benefit to long term fat loss. High effort strength training, sprinting, and high-intensity-interval-training DOES enhance fat loss due to depletion of glycogen stores and increased insulin sensitivity in muscle cells. Increased muscle mass from strength exercise will accelerate that rate at which fatty acids can used for fuel.

      • I think this is probably true Erick, but the data showing increased insulin sensitivity in HIT are in folks who are typically lean and already quite insulin sensitive. So I think the open (and in my opinion more important) question is, how much of an impact will this have in obese and/or insulin resistant folks. It’s certainly a plausible idea, I just haven’t seen great data suggesting it. As far as “slow” cardio, though, you’re right. Good data here suggesting that few extra calories burned during the activity are at least (if not more than) made up for in subsequent eating.
        More importantly, perhaps, is that HIT is fun and helps with all sorts of valuable activities (other sports, activities of daily living, retention of muscle mass).

        I would consider it a tragedy, however, for someone is overweight or IR to think HIT is the best first-line treatment. Fix the diet FIRST, then worry about which form of exercise.

        • You are correct; HIIT is never a good idea for de-conditioned overweight individuals (Why I hate the biggest loser). I always start beginners with resistance training using sufficient rest intervals. The results we are achieving may be due to the improved sense of well-being associated with goal oriented exercise; this may contribute more to dietary(low carb) compliance and less to improved insulin sensitivity.

        • Peter, your last statement here is where the fitness industry has it all wrong. The first thing they do to an overweight or obese person is make them get on a treadmill or cross trainer. Then they proceed to give them an expereince (they feel like they are going to die) that for most people will scare them into not coming back. In hindsight this is probably the best thing, but no one has mentioned the war(their diet)to them. I was a train first, nutrition later kind of man, but no more. Nutrition maketh the man, exercise finish of the good look.

        • Peter, well said. For those who are obese, Fix the diet FIRST, then worry about which form of exercise.

          On similar lines, those who are active yet overweight/obese (as I was/am) probably need to fix their diet and increase the intensity of their workouts to loose weight continuously till they reach their goals.

          I know a couple of people who have been on a ketogenic diet (Atkins induction phase) for many years and are overweight/obese. They lost some weight initially and then just stopped.

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