What is a Calorie?

A calorie is a unit of measurement. This unit measures the food we eat, and the energy we use.  We count food and exercise in calories.  Scientifically, a calorie (With a small c – as in calorie) is the energy required to raise a gram of water by one degree Celsius. A Calorie, or calorie with a large C, is the energy required to raise the temperature of one kilogram of water by one degree Celsius.

When we refer to a calorie, we are referring to a Calorie. Or also known as kcal. It is called a kcal because it contains 1,000 calories – or the energy to raise a gram of water by one degree Celsius. The fact we use the term calorie for kcal or Calorie is the fact that it is less confusing to speak about energy in the terms of thousands.

Macronutrient Calorie Count

  • Protein contains 4 calories per gram.
  • Carbohydrates contain 4 calories per gram.
  • Alcohol contains 7 calories per gram.
  • Fat contains 9 calories per gram.
  • Fiber contains 0 calories per gram.

Now that last number, zero, is misleading. Fiber does contain calories. But Fiber is complex carbohydrates which are not readily broken down by your stomach, and do not raise insulin or glucose levels. Due to this, it is believed Fiber does not add energy to the body, so most do not count the energy in Fiber again our caloric consumption.

The truth is, a gram of fiber contains roughly 2 calories per gram. Most people simply do not count fiber when counting calories because they do vary. Some forms of fiber do break down in your intestines to count as calories, as others do not. Due to the nature of not knowing, it is listed as zero. We cover Fiber more in depth in our article on Fiber, The Full Scoop on Fiber.

How Many Calories Do I Need?

The ideal method for people new to nutrition is the Rule of Ten (Or Eleven). You take your weight and multiply by ten. That is roughly how many calories a woman should consume in a day. For a man, take your weight and multiply by eleven. This gives you roughly the number of calories you should consume in a day.

The reason I suggest the ten methods is the truth is complicated. Calorie requirements vary wildly. From activity level to individual hormone levels, we just do not have a completely accurate method to determine how much we should eat.

What are Empty Calories?

junk food

An empty calorie is a calorie which is essentially void of nutritional value. As in, no vitamins, fiber, or amino acids. These calories, like those found in cake and pastries, provide the body nothing but calories for activity. This is fine if you need the calories and already have sufficient nutrients. If not, you are just eating food which will convert into fat storage.

Why Use Calories?

In the United States of America, we use calories as a unit of measurement. In Europe, they use Joules. Lucky for Americans, most food labels in Europe also include the caloric information.

During early nutritional work in the United States, the common dictionary did not have another word which would have to mean in relation to heat. Due to this, the calorie was used as Joules was not in the common United States dictionary.  After it was published, it became ingrained in the American lexicon and was adopted by most researchers going forward. Eventually, the American Government adopted its use in the RDA or Recommended Daily Allowance in 1943. Then, as they say, the rest is history.

This is puzzling because both a Joules and a calorie are units of energy measurement. They are both also a part of the metric system. A joule is just the energy required to move one Newton one meter. The use of kcal when mentioning calorie is just a way to simplify energy for the layman.

Counting energy in terms of thousand only serves to confuse people. In addition, when speaking of calorie value of items, it is a lot easier saying 4 calories per gram, than 16.8 calories per gram when describing the energy in one gram of carbohydrates.

Easy Conversion Data
  • Protein: 4 calories per gram (16.8 joules/gram)
  • Carbohydrate: 4 calories per gram (16.8 joules/gram)
  • Fat: 9 calories per gram (37.8 joules/gram)
  • Alcohol: 7 calories per gram (29.4 joules/gram)
  • For quick conversion, one calorie is equal to 4.18 joules.

Why Care About Calories?


This is a complicated question. The reason we care about calories is that until recently, we simply never had the opportunity to eat what we want when we want. In fact, it was not until the 1900’s that people had access to a variety of foods at our convenience. Before that, we did not have grocery stores which had imported foods from across the globe.

Now that we have access to anything and everything, people are inclined to make the wrong choice. To make matters worse, the restaurant industry is designed to produce food cheaply, quickly, and to appeal to as many people as possible. This gave advent to artificial sugars and trans fats which are designed to extend shelf life on the products we use every day.

Before this food revolution, people would go to the market to buy fat which was expensive, vegetables which were fresh, the bread which was fresh, and meat which was fresh. Foods like pasta or desserts were made at home, and were time-consuming and expensive. Due to this, our diets were far healthier naturally until the mid-1900’s.

The Cost of Convenience

Now that food, especially food which would traditionally not be healthy, is readily available cheaply, the consumer needs to understand what they are consuming. A simple calorie count if a lot easier than trying to understand the Macronutrients and Micronutrients we should consume daily. If you know the sleeve of Oreo’s contains more calories than you should eat in a day, you are more likely to pass on the sugary treat.

The ramifications for eating too many or not enough calories is also far easier to understand than a deficiency in specific nutrients. If you do not consume enough protein, you are likely to have a litany of problems ranging from muscle weakness to decreased cellular turn over. But if you do not eat enough calories, you know you will lose weight and appear thin. If you consume too many calories, you will gain fat. Along with this comes increased heart disease and risk for diabetes.

Calories are the short hand way to understand what your body needs. Are calories perfectly accurate? Not even close. Do they tell the whole story? Far from it. But unless you plan to calculate the sugars, carbs, fats, and protein in every morsel of food you eat, the universal calorie count will not only make sense but save time.

Find all the resources used in this article and the scientific basis of all our article at The Science Behind Fitness.

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