Calories – a topic that seems to push me from zero to rant mode in 2.3 seconds. You hear people say calories count. Others say they don’t. And in the end, with the punters on the ground, it leads to nothing but confusion. I’ll try to give my take here, touching a bit on Robb Wolf’s latest post, and the buzz word de jour – nutritional ketosis. I’ll try to do so without spiralling down into some form of frothing-at-the-mouth incoherence.
A calorie is a calorie?
Here is a comment I left on Gary Taubes’ blog on the topic;
Saying a calorie is a calorie is no more useful in describing what is happening at a physiological level than saying a metre is a metre. Both are units of measurement, useful in our physical worlds – for measuring stuff – but completely bloody hopeless for understanding our biology.
If I say I have a metre of wood, a metre of glass, or a metre of string, does this tell me anything much about these things other than how long they are? Assuming a metre is a metre, they must all be the same… they must all have the same properties, because I can quantify some aspect of them all similarly. What if we took two substances, in an identical amount, such as say, testosterone and oestrogen (I assume you could probably even quantify a caloric measure of these hormones – they “burn” after all). Do we automatically assume, once you feed them into the body, they each have identical effects because they can be quantified identically? Of course not. Yet we make the same mistake with fructose, glucose, palmitic acid, lauric acid, tryptophan, tyrosine, and so on.
I have only a nutritionist’s understanding of biochemistry (read as: relatively basic), but I understand, when we move away from their gross macronutrient labels, that each of those compounds will elicit a different downstream response… will send a different signal or message to our biology. I can’t for the life of me fathom why anyone would think these different compounds, even if corrected to be calorically equal to each other, would be identical in their effect on the body.
Let’s define a nutritional calorie… from Wikipedia;
The large calorie, kilogram calorie, dietary calorie, nutritionist’s calorie or food calorie (symbol: Cal) approximates the energy needed to increase the temperature of 1 kilogram of water by 1 °C. This is exactly 1,000 small calories or approximately 4.2 kilojoules. The calorie, the kilocalorie and the kilojoule are in common use in nutritional contexts as units of food energy. As used in these contexts the calorie (unprefixed) is based on the kilogram whereas the kilocalorie is based on the gram. That is, the nutritional calorie is the kilogram calorie and the kilocalorie is one thousand gram calories. Thus, in nutrition, the terms calorie and kilocalorie refer to equivalent units.
So what we are talking about when we talk about calories, to be correct, is a measure of the physical properties of proteins, fats, and carbs, external to a biological system. A calorie is a way for us to physically quantify the energy contained within those macronutrients [outside of a biological system] in much the same way as we can physically quantify the length and mass of something. But what about within a biological system? What is relevant there? Well if we are going to be concerned with energy in a biological system, we are better off quantifying proteins, fats, and carbohydrates by how much potential they have for ATP production – the actual energy currency of the body.
- Each molecule of glucose (carbohydrate) metabolised will yield between 36-38 ATP’s (aerobic)
- Each molecule of palmitate (fat) metabolised will yield 106 ATP
So, everything else being equal, palmitate will provide your system with more energy than glucose…
Now there are a couple of points from here already (and I’m purposefully not going to go through all the biochemistry of it all here – consider that extra for experts if you want to deploy your Google-fu)… When we start to look at the energy yield in a biological system rather than in the physical (calorie) world, to be accurate, we need to look at individual molecules of the various substrates.
We cannot lump all carbohydrates together.
We cannot lump all fats together.
There are many different ways in which glucose differs from fructose when we start to look at metabolism (and the hormonal responses each elicit in the body). Likewise, there are different ways in which, say, lauric acid (a medium-chain [12C] saturated fat found in the likes of coconut oil) differs from palmitic acid (a long-chain saturated fat [16C] saturated found in the likes of steak). Technically, we would say lauric acid and palmitic acid are both saturated fats, and being fats, they yield 9kcal per gram. But in the biological system of energy production, the 12-carbon lauric acid yields roughly 57-58 ATP, whilst the 16 carbon palmitic acid yields 106 ATP, with both being handled quite differently from digestion, to absorption, to metabolism.
The way in which we quantify them in the physical world, as the macronutrient “fat”, gives no insight at all into how they are treated in a biological system. It is like saying that retinol, cobalamin, and ascorbic acid are all the same because they are all “vitamins”. We need a bit more fidelity in how we talk about these things. A calorie is not a calorie in the same way that a macronutrient is not a macronutrient, or a vitamin is not a vitamin.
There is no central calorie counter in the body – period. There is no running tally, or end of day summation and gross adjustment. What the body does do, however, is respond to momentary fluxes… how much fructose or ethanol is arriving at the liver; what is the status of blood glucose, liver glycogen, muscle glycogen; how much oxygen is available; what is the demand of the muscles, brain; what are intramuscular triglyceride stores like; what is the stress status of the system; is the system in fight/flight mode or is it in rest and digest mode?
All of these processes and many, many others will dictate the delicate fine-tuning of the system. And there is obviously many things which can disrupt the balance of this fine-tuning – some of which we are only just starting to come to grips with (e.g. gut bacteria). How you run your ship on a day-to-day basis will often dictate the “disposal capacity” you have for the various substrates. Compare someone who is a relatively squishy office worker, interested in only doing a bit of low-level walking a few days per week, to a fire-breathing super-lean Crossfitter intent on WODing themselves within inches of their life 4-5 mornings per week. These two very different individuals are going to have very different disposal capacities for the food that they eat.
The walker, because they are not fluxing their glycogen stores so routinely, might be able to sit at the lower end of the carbohydrate scale, get away with not very much protein – they aren’t doing that much damage that they need to oversupply the basic building blocks [amino acids] for repair, and due to their low-level aerobic metabolism with walking (AND – the predominate muscle fibre type they are using to do it), they can probably run quite happily with the fat from a bit of steak and butter in the mix.
The Crossfitter, however, is a lean, mean, fast-twitching anaerobic monster. They give themselves the beat down several times a week, and they try to stay reasonably active outside of this (let’s say they are a fire-fighter, so they aren’t sedentary). They eat clean, so they aren’t getting a mountain of glucose and fructose just by the default of eating and drinking junk. But they are fluxing a good deal of glycogen through both their muscles and liver, giving them a bigger “disposal capacity” for glucose and fructose (fructose being great at restocking liver glycogen – if you create the capacity for it to do so). Having a preponderance toward more and larger fast-twitch fibres, their muscles tend to flux more glucose/glycogen through them, and they don’t have a huge capacity to store and utilise intramuscular triglycerides (so the disposal capacity for triglycerides [fats] is relatively low – the amount they get from dietary sources, naturally, is generally plenty). This person has a good “disposal capacity” for more amino acids in the mix (a higher protein intake), and more glucose and fructose (carbs). The small(ish) amounts of fat derived from their clean eating is enough for them.
Now let’s say that someone advises our walker to dramatically shift up their fat intake… because “if you eat more fat, you burn more fat” (and as I heard at a recent conference, “It is IMPOSSIBLE to eat too much fat”… Where is it going to go with our walker? Sure, they can fuel their day-to-day activities with fat, and they don’t need a lot of carbohydrate. But without increasing their “disposal capacity”, by doing more exercise, creating more of a flux of ATP (which in their case, can be replaced through fat metabolism, predominantly), where are they going to put it?
And our Crossfitting Fire Fighter… they decide to give very low carb nutritional ketosis a go. They are already lean, but it seems that in this paleo/Crossfit world, you just can never be lean enough. And hey, if some big dude can drop 20kg on that approach, then surely our Crossfitter can drop an easy 2-3kg to look like someone out of Fight Club? Where might things go wrong?
For a start, their training patterns, activity levels, and muscle fibre type all dictate they are better running on a higher glucose/fructose mix. The fibre type that gives them the power of a locomotive in a WOD (type II) doesn’t run particularly well on fats as a fuel – they have a lower capacity to shuttle fats into beta oxidation. Simply throwing more fat down the gob isn’t going to change this (unless they also want to change their training patterns and gain some type II fibre adaptation toward a more oxidative metabolism). And because they have heard that you can overeat protein, they cut this too. You can see a mile off what is going to happen here. A crash is coming. They will end up tired and miserable, their training will suffer, and their health will take a step backward. And no, it isn’t because they didn’t do it hard enough or long enough.
We could reduce both of the above examples to “calories count”. The first person [walker] is now “eating too many calories”, and the second person [Crossfitter] “isn’t eating enough calories”. These statements are true, to an extent, if you always interpret “calories” to mean some combination of saccharides, fatty acids, or amino acids. The walker is eating too many fatty acids for their ability to actually utilise them. The Crossfitter is not eating enough starches (as a source of saccharides), to match their fuelling requirements. What this doesn’t mean is that they now need to count calories coming in and calories going out, and try to balance that equation.
This reduction to calorie counting is my fear when I read the likes of statements from Robb such as “CALORIES MATTERED MORE THAN CARBS FOR BODY-COMP.” I fear that people will suddenly think they need to start counting the water-heating numbers coming in and going out. The way I read the above statement from Robb (and he is free to jump in here and correct me), is that he went from being very active and having the ability to dispose of all of the energy substrates he was eating, to not being that active and thus diminishing his substrate disposal capacity. The answer for him was not to simply reduce his glucose/fructose intake, and still keep eating a mountain of fatty acids, as if the absence of one in the diet causes the other to simply evaporate. The fact that he wasn’t moving as much meant he didn’t need as much of the raw materials (food) going in his “pie-hole”. But I am picking (hoping), he didn’t sit down and decide he needed 1800 cals per day and calorie counted his food. He didn’t reduce his eating to a mathematical equation. How very tedious if he did.
If you “cut calories”, what do you do? You eat less FOOD. Food which contains mixtures of glucose, fructose, palmitic acid, lauric acid… and so on. The opposite if you “increase calories”. If we took the Crossfitter example above, cut their carbs and protein, ramped up their fat, and ensured that it was all balanced out from a calorie counting perspective – let’s say 3500 in to account for 3500 out – will it change anything? Will getting them to eat the correct number of calories, mostly from fat, change anything about the type of muscle fibres they have, or the type of glycolytic activity they participate in, or the muscle wrecking nature of wrangling fire hoses and carrying BA gear on their backs?
No. Quantifying food and diet through “calories” says nothing of qualifying the needs of the individual. Simply calorie counting misses entirely that you need to take a horses for courses approach.
Let’s look at a couple of recent contrasting real world examples to see if we can illustrate the point further… next time.