You must have heard this phrase so many times by now – “Calorie is a calorie is a calorie…”. Personally, I find this phrase to be a complete nonsense. It doesn’t make any sense mathematically as people just state the obvious. It doesn’t even make sense semantically, again, as people are just stating the obvious – a thing is a thing is a thing – there is no new information in this sentence! Maybe there is some sort of a psychological meaning to it? Like, asserting that a calorie is a calorie and should be treated as such… I don’t know if it helps anyone, but ultimately from a biochemical standpoint it also doesn’t make sense. Simply because it’s not true! Let me show you why!
What is a calorie?
Calorie is a unit of heat or energy that is being released when some substance is being burnt or metabolized. Historically, it has been used by scientists who studied thermodynamics and then – bioscientists to describe heat along with joules, which are used to describe energy in general. One calorie is defined as the amount of energy required to increase the temperature of 1 g or 1 ml of water by 1 centigrade. And here, even on the level of definition, we have another problem. One thousand calories is… a Calorie. How is it possible? Well… there is a bit of history there, but there are effectively two calories:
- A small calorie, or a gram calorie (denoted as cal) is the amount of energy needed to increase the temperature of 1 g or 1 ml of water by 1 centigrade;
- A large calorie, or food calorie, or kilocalorie (denoted as Cal or kcal or… calorie) is the amount of energy needed to increase the temperature of 1 kg or 1 L of water by 1 centigrade.
And just to be precise 1 Cal = 1 kcal = 4184 J. Also, please note, that this amount varies slightly depending on the initial temperature of water being heated.
Ok, the scientific terminology issues aside, even if we are talking about the same calories, they are still not the same i.e. a calorie that food contains is not the same as the calorie absorbed and not the same as a calorie used. Let me elaborate further.
Calories, calories… and more calories
Pretty much all organic substances have certain amount of energy stored in the form of chemical bonds and this energy is normally released via oxidation. For example, if I take a sheet of paper and burn it, it will produce some heat or some calories. The interesting part is that if I were to eat the same sheet of paper, I wouldn’t get any calories from it, because my (and yours) digestive tract cannot extract energy from cellulose, the main component of paper. My point is that the calories consumed are not the same as calories that are being absorbed.
Since we are talking about absorption, this process takes time and… energy. As we process nutrients, we need to break them down to their constituents such as fatty acids, monosaccharides, and amino acids etc. (check my blogs on that, by the way). So, at the end of the day we need to spend some energy to get these nutrients into our system and this energy is usually released as heat, something that we call thermic effect of food (TEF). TEF may be pretty high – up to 25-30% of the nutrients’ caloric value for proteins. So, for example when we digest 100 calories worth of protein, we might need to spend 25-30 calories in the process and the net gain of energy is around 70-75 calories. The calories consumed are not the same as calories available.
Finally, we use most of nutrients not only for energy, but we also use them to build structural elements of our body, such as proteins. If we continue the same example of protein, we might not use this protein for energy at all – all of it can be incorporated into our tissues as muscle protein for example. So, not only we won’t get these 100 calories, but we will spend 25-30 calories to absorb the amino acids and then some unknown amount of energy to build our own protein from them. Calories available are not the same as calories used.
So, the bottom line is that the calories contained in food we consume are not the same that we extract and make available for ourselves, and also, on top of that, having calories available doesn’t necessarily meant that we are going to use them. Thus all this calorie math gets completely rearranged.
I hope that you can see how “a calorie is a calorie is a calorie” doesn’t make any sense on any level – neither mathematically, nor semantically, nor biologically. It is just not the case, and we need to be aware of at least some details of the biochemical processes occurring in our bodies in order to be able to optimize our nutrition and to achieve our goals, whether it is muscle building or fat loss. And I hope that here, in my blogs, or on my YouTube channel you will be able to find some answers. So, subscribe and, of course, ask questions, make comments and suggestions. All constructive interactions are welcome!