From in the news, to magazine articles, to on the back of every food product there they are: calories! But what exactly is a calorie? How many calories are too much? What exactly is the relationship between calories and losing weight?

If you’re curious about any of the above answers, or simply just want to know more about the human body and metabolism, keep reading!

Calorie Defined

A calorie is a unit of measurement, specifically: energy. It is the amount of energy needed to increase the temperature of 1 gram of water by 1°C. However, this isn’t the same calorie you hear so much about!

In terms of nutrition and everyday use, using the calorie would lead to exorbitant numbers (think of having something so large as a 20,000 calorie diet, yikes!) For diet purposes, the Calorie was invented. Instead of the amount of heat required to raise 1 gram of water by 1 °C, the Calorie is the amount of heat required to raise 1 kilogram of water by 1 °C . For simplification purposes, however, it’s assumed that whenever talking about nutrition that the Calorie is being used no matter the capitalization.

What Calorie Means For You

But I know I know, enough about numbers. What do these all mean for me and my body?

Well, as you know, every day we eat numerous types of foods (sandwiches, pasta, hamburgers) and imbibe various types of liquids (waters, juices, sodas). These all contain numerous amounts of molecules in the form of proteins, carbohydrates, and fats.

When we eat these things, our body converts them to fuel for our everyday use. Just how much energy these foods give us is defined as a calorie, and different foods give us different amounts of energy.

The exact amount of energy depends on the molecules present in the food, and at what amounts. Carbohydrates and protein both give 4 calories per gram, while fat gives more than double that, at 9 calories per gram. It’s easy to see now why a slice of cake with carbohydrates and fats has a lot more calories than a slice of bread with just carbohydrates, isn’t it?

What Happens if You Consume More Calories than Your Body Needs?

You gain weight! Just how much depends on exactly how many calories you consumed in excess, along with a bunch of other factors such as personal metabolism. This relationship works the opposite way, as well — if you use more calories than you consume, you’ll lose weight, as your body needs to break down the stored fat for energy.

On top of that, everyone has different calorie needs. At the basic level, we need a certain amount of calories just to sustain the normal upkeep of our body– like keeping our hearts beating and our brain thinking.

But the amount of calories a person needs is also dependent on gender: men tend to need more calories than women. Activity level also has a big effect on calories as well. A marathon runner needs a lot more calories than an office worker! You can now see why it’s hard to find a calorie value per day that’s suitable for everyone, with everyone having different body types, different levels of activity, and different levels of metabolism.

Conclusion: General Rule on Caloric Intake

As a general rule, however, a person should consume about 2000 calories per day (this is why you see nutrition facts based off a 2000-calorie diet). This amount isn’t tailored exactly for your specific needs though– you’d need to do some calculations or see a registered dietician to figure out just exactly how many calories your body needs on average. That being said, 2000 calories a day is a good general guideline to follow.