What Is a Calorie?

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Calories in the foods we eat provide energy in the form of heat so that our bodies can function. This means that we need to eat a certain amount of calories just to sustain life. But if we take in too many calories, then we risk gaining weight.

To make matters even more complex, all calories are not the same. You can consume 150 calories by eating a candy bar, for instance, or by eating 30 cups of lettuce. Understanding exactly what a calorie is, and why we count them, can help you make better dietary decisions.

Calorie Definition

A calorie is a unit of measurement. Specifically, it is defined as the amount of heat needed to raise the temperature of one gram of water by one degree Celsius.

Though, when the word "calorie" is used in reference to food, people are usually actually talking about the amount of kilocalories a specific item has, which is what is listed on nutrition labels. One large kilocalorie (kcal) is the equivalent of 1,000 small calories.

The foods we eat supply our bodies with calories, providing the energy we need to live and stay healthy. Everything we do relies on the energy that comes in the form of calories, whether it is sitting on the couch for hours at a time or running a marathon.

Part of the confusion with calories comes in because calorie count alone does not whether a food is nutritious. It is more about the type of calorie, such as whether it supplies vitamins, minerals, and fiber or if it is void of nutrition and more of an "empty calorie."

Calories and Weight Gain

Calories in food provide essential energy, but if you consume too many you will gain weight. These excess calories are stored as body fat. Your body needs some stored fat to stay healthy. But too much fat can cause health problems.

So how do you make sure that you don't eat too many calories? It's important that you understand your caloric needs. That is the number of calories your body needs to perform basic metabolic functions and daily physical activities. You can calculate your caloric needs using an online calculator.

The daily recommended caloric intake for the average American can range from 1,600 to 3,000 calories per day. But that number is a general estimate and there are many variables for individual needs. Men can eat a little more, women should eat less because their bodies are smaller and need less fuel. Your individual calorie needs depend on several factors such as your activity level and metabolism.

Calories in Food

Different types of food provide different levels of energy. That is, the three macronutrients are not all equal in the number of calories they provide. Protein and carbohydrate have less than half of the calories per gram as fat does.

Macronutrient Calories per Gram:

  • Carbohydrate: 4 calories per gram
  • Fat: 9 calories per gram
  • Protein: 4 calories per gram

Because fat provides more calories per gram, many healthy eaters try to limit the amount of fat in their diet. But some types of fat are necessary for a healthy body. Polyunsaturated fat, for example, helps you to maintain a healthy heart. And even though carbohydrates provide fewer calories, refined carbohydrates provide fewer nutrients than complex carbs.

So are all calories the same when it comes to weight loss? Experts generally agree that a calorie is a calorie. It doesn't necessarily matter where your calories come from. To lose weight, you need to consume less and burn more.

However, some calories provide weight loss benefits. For example, calories from protein are helpful in building and maintaining muscle. When you have more muscle, you are better able to stay active during the day and burn more calories. And calories from foods rich in fiber help you to feel full and satisfied throughout the day, which is helpful when trying to lose weight.

How to Count Calories

Keeping track of your calorie intake helps you better understand the amount of calories your body needs to lose, gain, or sustain a certain weight. Whatever your goal, knowing how many calories you are eating is key to getting the desired effect.

One way to count your calories is by keeping a food diary and writing down everything you eat, then looking up each item's calorie count. Another option is to download an app that counts your calories for you.

Experts estimate that if you consume approximately 3,500 excess calories you will gain one pound, though this has been disputed. Along the same lines, if you want to lose one pound, you need to create a calorie deficit

You can reduce your caloric intake by 500 calories per day to lose 1 pound each week. A 1–2 pound decrease in weight per week is considered a healthy and sustainable rate of weight loss.

The most important thing to remember is to not cut calories too drastically. Going on a very low-calorie fad diet can put your health at risk and cause health problems.

A Word From Verywell

There are many different ways to follow a healthy diet that supplies the energy your body needs to lose, gain, or sustain a particular weight. Counting calories is just one. Portion control and choosing nutrient-rich foods are important factors too.

The thing to remember is that there are no "good" or "bad" calories, or even foods. Instead, the better you understand what a calorie is and why you should care, the easier it is to make choices about which calories will help you reach your specific goals.

If you want to learn more about your own calorie needs, check out our recipes and use the recipe nutrition calculator to see how many calories are in your favorite foods.

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Article Sources
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  1. U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015–2020 Dietary Guidelines for Americans. 8th Edition. December 2015.

  2. Hall KD, Chow CC. Why is the 3500 kcal per pound weight loss rule wrong?. Int J Obes (Lond). 2013;37(12):1614. doi:10.1038%2Fijo.2013.112