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 when making 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.

When the word "calorie" is used in reference to food, people are usually actually talking about the number 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 calories we eat supply our bodies with the energy needed 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 or running a marathon.

Calories by Food Type

Part of the confusion with calories is because calorie count alone does not dictate whether a food is nutritious. If a food supplies vitamins, minerals, fiber, or protein, its calories deliver more value to your body; these foods are sometimes called "nutrient-dense." If the food is void of nutrition, it may be called an "empty calorie" or "energy-dense" food; it provides calories (or energy) but few nutrients.

Different types of food provide different levels of energy; the three macronutrients are not equal in the number of calories they provide. Protein and carbohydrates supply less than half of the calories per gram as fat.

Macronutrient Calories Per Gram

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

Because fat provides more calories per gram, some people try to limit it 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 than fat, refined carbohydrates provide fewer nutrients than complex carbs. Refined carbs are more energy-dense, while complex carbs are nutrient-dense.

Recommended Daily Caloric Intake

The 2020–2025 Dietary Guidelines for Americans indicate that the daily recommended caloric intake for adults can range from 1,600 to 3,200 calories per day. This is a general estimate, as there are many variables to consider when determining an ideal daily caloric intake.

For instance, the calorie needs for males are slightly higher (2,200 to 3,200 calories per day) than the needs for females (1,600 to 2,400 calories daily) according to these guidelines. Your caloric intake also depends on other factors, such as your age, activity level, and metabolism.

Calories and Weight

It is often estimated that if you consume approximately 3,500 excess calories you will gain one pound, though this has been disputed. But what's not controversial is that if you want to lose weight, you need to create a calorie deficit: Take in fewer calories than you use.

Calories and Weight Loss

Some weight-loss experts believe that a calorie is a calorie. Their philosophy is that, to lose weight, you simply need to consume fewer calories and burn more. However, some calorie types 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 feel full and satisfied throughout the day, which is helpful when trying to lose weight.

Using an online calculator can help you determine how many calories your body needs to lose weight based on your age, height, sex, activity level, and weight loss goal.

It's important not to cut calories too drastically, unless you are specifically directed to do so by your doctor. Going on a very low-calorie diet can put your health at risk and cause problems such as constipation, nutrient deficiencies, and gallstones.

A 1- to 2-pound decrease in weight per week is considered a healthy and sustainable rate of weight loss.

Calories and Weight Gain

Calories in food provide essential energy. But if you consume too many, you can gain weight. These excess calories are stored as body fat. Your body does need some stored fat to stay healthy. If it stores too much, though, it can lead to health issues.

How do you make sure that you don't eat too many calories? The first step is to understand the number of calories your body needs to perform basic metabolic functions and daily physical activities. Calculate this using an online calculator.

Once you know this number, you can create an eating plan that provides this approximate calorie count without going over it. This will help keep you from gaining weight while also helping you maintain your previous weight loss.

How to Count Calories

Keeping track of your calorie intake helps you better understand the number 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.

Frequently Asked Questions

How many calories should people eat every day?

The general range for adult females is 1,600 to 2,400 calories per day. For adult men, it's 2,200 to 3,200 calories daily. However, the amount of calories you need depends on a variety of factors such as age and activity level. Using an online calculator can help you determine your individual calorie needs.

What percentage of calories should come from each macronutrient?

The 2020–2025 Dietary Guidelines for Americans recommend that your diet be split according to these percentages:

  • 10% to 35% protein
  • 45% to 65% carbohydrates
  • 20% to 35% fat

What are high-calorie and low-calorie foods?

A food is considered high-calorie if it has 400 calories or more per serving (think a fast-food double cheeseburger or two scoops of ice cream). while low-calorie foods contain around 40 calories per serving (leafy greens, veggies, shrimp, air-popped popcorn).

What are empty calories?

Foods that offer the body very little nutrition, if any, are said to provide empty calories. Soda, chips, and baked desserts all fall into this category.

What are low-calorie and very low-calorie diets?

A low-calorie diet is an eating plan that supplies around 1,200 to 1,500 calories each day while a very low-calorie diet is closer to 800 calories per day. Consuming too few calories can be harmful to your health, so a very low-calorie diet is only recommended when under a doctor's supervision.

How many calories per day are recommended for weight loss?

Everyone is different, so the number of calories you need to lose weight depends on your sex, age, activity level, and more. Reducing your calorie intake by 500 calories per day is often recommended, but it's better to personalize your calorie goal. To do that, you can use a weight loss calculator or consult with a registered dietitian.

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 maintain weight. Counting calories is just one. Portion control and choosing nutrient-rich foods are important factors too.

Remember that there are no "good" or "bad" calories, or even foods. Instead, the better you understand what a calorie is and how it may affect your body, 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 a few healthy recipes and use a recipe nutrition calculator to see how many calories are in your favorite foods.

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13 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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