What does that mean? First, let’s break down what a Calorie actually is, and why it’s important to pay attention to them.
While it may seem nit picky, whether or not that beginning “c” is capitalized really matters. Little “c” calorie refers more to a scientific amount of energy, 4.2 joules to be exact. Big “C” Calorie is also energy, but 1000 times more energy; 4.2 kilojoules. When it comes to food, we’re always talking about big “C” Calories. Over time, the capital has been stylistically dropped. It’s a bummer for science, but easier for the consumer. Some people, trying to stay in tune with both science and the general populace have adopted “kcal” as a way to refer to food Calories.
A Calorie is essentially how much energy is provided by that item, 1 Calorie is enough energy to raise the temperature of 1 kg water by 1 degree Celsius. So, the Vega Sport Energy Bar, which has 200 Calories, contains enough energy in it, that if it were burned, it would warm up 200 kg (about 53 gallons) water by 1 degree Celsius.
How the body uses Calories is really interesting. The basic amount of energy needed to keep your body functioning is your metabolism. That amount can actually be measured or predicted in Calories. It’s very useful knowing your basic metabolic rate (BMR) if you’re an athlete trying to stay properly fueled, or someone trying to lose/gain weight.
When you EAT a Calorie, it’s a Calorie. Meaning if you eat too many Calories from fat, carbohydrates or protein, the body will take those unused Calories, convert them and then store them as fat. To be blunt, fat gain comes from overeating in general, not necessarily overeating in one particular macronutrient.
Now, once those Calories are stored, you have fat Calories, carbohydrate Calories (in the form of glycogen), and protein Calories, and they do NOT easily interchange. A Calorie is no longer a Calorie. Fat burns at a different rate than glycogen or protein, so it is not used as a fuel source at all times, unlike carbohydrates, which are always part of the energy burn process, hence why athletes need to consider carbohydrate intake. The fat burn rate is generally at less than 75% of your maximum exertion rate.
If you are a typical high intensity athlete, and engage in true high intensity activities, it’s possible that most, if not nearly all, of your Calorie burn is coming from glycogen, and NO, or very little, fat. If the name of the game for you is exercise for fat burn, you likely need to slow way down, until the point where you can easily hold a conversation without gasping or taking intermittent big breaths of air. If you’re an athlete and you know your endurance and anaerobic/aerobic thresholds, fat burn is best done in the endurance stage. Once you hit that anaerobic stage, you’ve passed fat Calorie burning land.
If you’re struggling with your weight, use tools such as the Harris Benedict or Cunningham equations to find out what your basic metabolic rate is, coupled with a Total Daily Energy Expended calculator (TDEE). In very basic terms, to maintain your weight, count your Calories and eat that exact amount. And to lose weight, take your TDEE and subtract 500, and eat that amount. But be warned, there is more to weight control than calories in and calories out, but that’s out of this article’s scope. Stay tuned for more about the Calorie in future blog posts.