Many, even most, diets are focused around calories. We all talk about them all the time. However, most people don’t even know what they are counting so carefully, and in reality, there is no way to really assess how many calories a meal will have for YOU. Understanding calories is important, as they can be a useful tool, and understanding can get you out of the counting duty.
A calorie is merely a unit of measurement, or one of two units, actually. A “small calorie” , represented by the symbol cal, is the amount of energy required to raise one gram of water by one degree Celsius. A “large calorie”, represented by the symbol Cal or kcal, is the amount of energy required to raise 1 kilogram of water by one degree Celsius. Of course, this means that 1 kcal = 1000 cal. The calories that you see on nutritional labels are actually the large calories, kilocalories (or kilojoules in Europe and Australia). Got it so far?
Plenty of people think of calories as a thing that is in food – a physical aspect of the food that is invading your body and making you FAT. Not so! Calories are just a way to describe how much potential energy a food – or anything else that can store energy, like coal, or natural gas – has in it. Calories themselves are not concrete – remember, they are just a unit of measurement, like an inch, or litres.
Originally, the calorie content of food was determined by literally burning the food whilst it was in water, and calculating how much the water heated up. That hasn’t been the process in a long time; now food labelling takes its information from the National Data Lab (or equivalent), which uses a method known as the Atwater system to determine the amount of calories in the individual aspects of each food: the protein, the carbohydrates, the fat, and the alcohols. An average number of calories is assigned to each component, based on the burning method of determination. Because the body doesn’t tend to absorb the carbohydrates in some fibres, the calories in those are usually subtracted before calculating the carbohydrate total calories.
Are you beginning to see one flaw in the strict calorie counting system? Before we even start to talk about absorption and individual digestion, already this is a system based on averages, and generic ingredients. This is still valuable information, however, the specific, to the single-digit counting that many people do to try and monitor their intake is not a very accurate description of the energy value of every single food.
The next piece of the calorie-use puzzle is our own bodies. We all know that people’s digestion, their metabolism, is individual. Don’t you have that friend that eats everything and never gains a pound? Are you the person who hasn’t been able to finish a full plate ever, because you feel full quite quickly? There are people who can’t digest certain foods easily, and people who can’t digest food at all – all of these aspects use energy, and it’s different for every person, for every meal. Your body uses energy, which is of course, calories, to digest foods, and sometimes it needs more energy to digest and use the nutrients in that food than at other times. Even the same food, with the same stated number of calories, might take more energy to digest on a different day, or combined with different other foods. There is no way to truly measure how many calories you are using, so you can’t really measure the number you are getting.
You need the energy in food for absolutely everything you do, including just being alive. Every human needs calories of energy to keep their hearts beating, their brains functioning, and their digestive systems doing their job. The exact number is… and I know you’re expecting this now… different for every person, and for every day. It is called the basal metabolic rate, and this is how the majority of the calories you consume per day are used.
Some estimates put the number of calories needed per day to just be a person on average to be between 1000-1400. It depends on your age, your height, your weight, your activity level, your stress level, the temperature, etc., etc. Match that with the idea that how you and your metabolism accesses the calories in food, and the fact that the stated number of calories in a food isn’t all that exact anyways, and you can start to really see how there is no clear way to know exactly how many calories you are taking in, how many you need in a day, and how many you are burning.
So, do I ever pay attention to calories? Yes, I do. As I said above, knowing how many calories you eat, approximately, and how many calories a meal has in general terms (even if you aren’t exactly sure how many it will have for YOU), is a useful tool to understand how your diet is contributing to your liveliness, what we call your “energy levels”, although after talking through the science, that term seems confusing! I find that many of my clients are not eating enough calories to give them the energy they need to live their busy, stressful lifestyles. Have a general idea of how much is going in, and comparing it to how you FEEL, is a first-step to eating better for a better, healthier, more vital life. We are busy people, we need energy – and we need to not waste any of that energy obsessively something that isn’t really telling us very much at all!