What Is a Calorie?

If you are like most people, you are probably confused about calories and their importance. Despite being villainized, calories are not a bad thing. In fact, they not only provide you with energy but are necessary for your survival. Additionally, calorie consumption that is too low or too high could eventually lead to health problems.

"Simply put, a calorie is the unit of energy our food supplies," says Stacey Pence, RD, a registered dietician at The Ohio State University Wexner Medical Center. "Our bodies use energy derived from the foods we consume, similar to how a car uses gallons of gas per mile."

The key is making sure you consume the right amount of calories for your body's needs, from high-quality sources. While a calorie is technically equivalent to a calorie, some foods are more calorie-dense than others even when the portion sizes are the same weight.

For example, 30 grams of spinach has significantly fewer calories than 30 grams of chocolate chip cookies—with spinach containing only 7 calories while chocolate chip cookies are 139 calories. For this reason, it may make more sense to consider the nutritional make-up of the food you're consuming as well as the number of calories. Here is what you need to know about calories including determining how much you need.

Calorie Needs

Calories from carbohydrates, fats, and proteins provide the energy that we need in order to function and live. Here are some things to consider when determining your calorie needs.

Basic Metabolic Functions

Your metabolism is responsible for converting food into the energy needed to do everything you need to live. How many calories someone needs to survive depends on their weight, height, age, gender, and medical status. This information helps determine your basic metabolic rate (BMR). It is normal for your measurement to be different from your partner's or best friend's.


Exercise also affects your calorie needs. You need more calories to fuel your workouts than what you need to do basic, everyday functions. The more calories you burn with exercise, the more you need. More nutritious foods will better fuel your exercise routines.

How many calories you burn during exercise depends on a variety of factors, including the type of exercise, duration, and body weight. You can use our activity calculator below to determine how many calories you burn per activity.

Factors That Affect Calorie Needs

Multiple factors affect the calories you need, such as height, weight, age, and gender, says Pence. Certain medical conditions and procedures also increase calorie needs. For example, you'll need more calories if you're getting cancer treatments or are healing from a recent surgery.

"The taller or larger your body mass, the more energy or calories our bodies utilize," Pence says. "As we age, our muscle mass tends to decline, which reduces our calories burned. Men tend to carry more muscle mass than women and therefore burn more calories daily."

But, you do have control over how physically active you are. The more you move, the more calories you burn, she adds. Some people add exercise to their routine so that they can consume more calories in a day's time and still lose weight.

Factors That Affect Calorie Needs

  • Height
  • Weight
  • Age
  • Sex
  • Medical status (specific medical conditions or procedures require more or fewer calories)
  • Muscle mass
  • Activity level
  • Environmental temperature
  • Hormonal status and pregnancy

Recommended Daily Calorie Intake

The 2020-2025 Dietary Guidelines for Americans show that the recommended daily calorie intake can range from 1,800 to 3,200, depending on age, weight, gender, and the amount of physical activity a person gets in a day.

It is important to note that these guidelines have more calories listed for men than women. A man's calorie needs range from 2,000 to 3,200, while a woman's calorie needs range from 1,600 to 2,400. However, this is a simplified guideline for how many calories someone needs every day, and individual needs may vary.

For a more accurate estimation of your daily caloric needs, you may want to consult a registered dietitian.

Calories in Food

A calorie is a calorie, but some foods provide more nutrition than others such as more protein, fiber, minerals, and vitamins. These foods are called nutrient-dense, while foods lacking nutrition are called energy-dense or empty calories.

Empty Calories

When a food or drink is high in calories but offers little or no nutritional value, it is often referred to as containing "empty calories." Typically, foods that fall into this category have high fat, sugar, or alcohol content and may be processed in some way. Some examples include cakes, cookies, candy, bacon, some condiments, and alcohol.

According to researchers at the USDA, Americans ages 20 and older consume a large number of empty calories each day. A study conducted in 2012 found that American men consume nearly 925 empty calories a day while American women consume nearly 625 empty calories. Consuming too many empty calories could impact weight management goals, leading to weight gain and increased risk of chronic disease, as well as lead to nutritional deficiencies.

Nutrient-Dense Foods

Nutrient-dense foods contain the vitamins, minerals, and nutrients you need to nourish your body without too much sodium, added fat, or sugar. In other words, nutrient density is the holistic amount of nutrients you get for the number of calories consumed.

Some examples of nutrient-dense foods include fruits, vegetables, whole grains, fish and seafood, unprocessed lean meat and skinless poultry, nuts, and legumes. But when trying to ensure you are getting what your body needs, it is best to focus on your overall eating pattern, rather than individual nutrients or specific foods or food groups.

Macronutrient Calories

As for the calories in your food, you may want to consider three macronutrients—carbohydrates, protein, and fat. Carbohydrates and protein each provide 4 calories per gram, while fat contains 9 calories per gram.

This knowledge may tempt you to eliminate fats from your diet, but healthy fats are an important component of a balanced eating plan. For example, polyunsaturated fat, which is found in foods like walnuts and salmon, helps keep your heart healthy.

Macronutrient Calories Per Gram

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

Low or No-Calorie Foods

When you're trying to lose weight, you may be tempted to load up on calorie-free or low-calorie foods that replace high-calorie sugar with calorie-free artificial sweeteners. While these "diet" foods were historically thought to promote weight loss, evidence suggests that products containing non-caloric artificial sweeteners may actually cause weight gain. In fact, research shows that artificial sweetener consumption contributes to metabolic syndrome and obesity.

No matter your goal, is it best to skip low or no-calorie foods that contain artificial sweeteners.

Calories and Body Weight

Calories may be a helpful tool for weight management, depending on your goal. For example, creating a calorie deficit will likely facilitate weight loss, while a calorie surplus can create weight gain.

Pence indicates that keeping a detailed food log (not just counting calories) can help you understand the types of calories you consume. For example, you can look back to see whether you're eating too many calories from sweets or fast foods or if you're making more nutritious choices by eating enough fruits and vegetables.

Add other details to your daily food diary, like how you feel after eating. For instance, you may want to note if you feel full or satisfied. Pence explains that doing so can give you more information on emotional eating habits or making poor food choices when feeling excessive hunger.

Calories and Weight Loss

If your goal is weight loss, you may want to consider counting calories. Not only can you budget what you are eating throughout the day, but more importantly, you can keep track of the nutrients you are getting.

"Counting calories can help with weight loss, just like balancing your bank account and budgeting can help with saving money," says Pence. "Each person has a certain number of calories they burn each day which varies per person. If you keep track of your calorie intake and make sure total calories consumed are less than the calories you burn, the result is weight loss."

Keep in mind that calories are not the only thing you should be measuring.

There are many other factors that affect weight loss, so you may benefit from looking at other parts of your diet, such as macronutrient balance and fiber. For example, you need about 10% to 35% of protein from your daily total calories to help build muscle. Muscle mass is critical for everyday activities and also impacts balance and stability. Additionally, if your goal is to lose weight, having more muscle can help you burn more calories.

Fiber is also crucial for losing weight and general health. Foods that are high in fiber help you feel full and promote satiety.

Be cautious when cutting calories. Not getting enough calories can cause health problems. For instance, you could experience nutrient deficiencies, abdominal pain, gallstones, and constipation. Avoid an extremely low-calorie intake unless a healthcare professional advises it.

Calories and Weight Gain

If gaining weight is your goal, you will need a calorie surplus. Keep in mind that different foods deliver varying amounts of nutrients. So even if your goal is to gain weight, make sure you choose nutritious foods like fruits, vegetables, beans, nuts, lean meats, and whole grains.

If you're having trouble eating a lot at once, try eating smaller meals throughout the day, and don't forget to include snacks, too. Think high-calorie, nutritious foods like hummus, peanut butter, protein bars, and trail mix.

If you're looking to gain weight, you may want to consider adding strength training to your routine. Exercise that includes weight lifting can build muscle mass and increase hunger, helping you to meet increased calorie goals.

How to Count Calories

Counting calories is a popular way to understand how much you are eating every day. It can also be a great way to understand more about the foods you are consuming including the nutrients and volume they provide.

If you choose to count calories, you may want to experiment with calorie-counting apps or a food journal to see which you like best. Just make sure calories aren't the only thing you are tracking. You may want to be mindful of the balance of carbs, protein, and fats, as well as fiber, vitamin, and mineral content.

While calorie counting may be helpful for some, there are drawbacks to be aware of. First, counting calories may lead to disordered eating habits. Second, the practice of counting calories can be cumbersome and time-consuming, leading people to eat similar foods each day (so they don't have to calculate new foods and combinations). This lack of diversity in the diet may lead to nutritional imbalances, but also can get boring quickly, leading to dissatisfaction.

There are many alternatives to counting calories if you're looking to gain or lose weight. Consider consulting with a registered dietitian to explore ways that you can hit your goal, without counting calories.

A Word From Verywell

Counting calories is just one way to keep track of your food intake. If you choose to count calories for weight loss or weight gain, make sure you are choosing nutrient-dense foods to fuel your day. Calories are not a bad thing, even if your goal is to lose weight. They are simply a unit of measure.

Remember that one calorie is one calorie, no matter what type of food or drink it comes from. Instead, focus on eating a balanced, nutritious diet that contains appropriate amounts of protein, carbs, fat, and fiber. If you need help understanding calories or are considering a weight management program, talk to a healthcare provider or registered dietitian for guidance.

Frequently Asked Questions

  • What is a calorie deficit?

    A calorie deficit means you are consuming fewer calories than you need, which often results in weight loss. Exercise, or any daily movement, increases caloric expenditure, which can create a deficit if you are not consuming as many calories as you are burning.

  • What is a calorie surplus?

    If your goal is to gain weight, you will need to consume more calories or have a surplus of calories. This is the opposite of a calorie deficit. For example, one study recommends a surplus of 10% to 20% of your daily recommended calories for weight gain. For example, if your daily calorie goal is 2,000, you may want to add an additional 200 to 400 calories. One medium banana and 2 tablespoons of peanut butter (approximately 300 calories) is an excellent example of a nutrient-dense snack that meets this surplus.

  • How many calories should people eat every day?

    The amount of calories you need depends on a variety of factors, such as your age, weight, height, sex, and physical activity level. The Dietary Guidelines for Americans 2020-2025 outline basic caloric recommendations for each age group. You may also want to try our online calculator, which is based on the Mifflin-St Jeor equation, for an estimate of how many calories you need every day. For more individualized guidance, consult with a registered dietitian.

  • What percentage of calories should come from each macronutrient?

    The Dietary Guidelines 2020-2025 recommend the following ranges for macronutrients from your total calorie intake: carbohydrates 45% to 65%, fats 20% to 35%, and protein 10% to 35%.

  • What are high-calorie and low-calorie foods?

    The definition of a low-calorie food is 40 calories or less per serving. A high-calorie food is something that has the same serving size as a low-calorie food but is higher in calories. For example, 100 grams of strawberries is 35 calories, whereas 100 grams of strawberry ice cream is 192 calories. Strawberries are a naturally low-calorie food, whereas strawberry ice cream is a high-calorie food.

  • What are empty calories?

    Empty calories are foods and drinks that are energy-dense but provide little to no nutrition. Some examples might include candies, sodas, potato chips, and baked goods.

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

    A low-calorie diet is typically about 1,200 to 1,500 calories a day, while a very low-calorie diet is about 800 calories. Because a very low-calorie diet is significantly below what is nutritionally sound, it may cause health problems, and should only be followed when recommended by a healthcare provider

  • How many calories per day are recommended for weight loss?

    A calorie deficit is needed for weight loss but depends on a variety of factors including your age, weight, health conditions, and goals. It's often recommended to cut about 500 calories daily to lose weight. But if you are considering losing weight, you should work with a registered dietitian who can help you make an individualized plan.

22 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.
  1. USDA, FoodData Central. Spinach, raw.

  2. USDA, FoodData Central. Cookies, chocolate chip, refrigerated dough.

  3. Rush University Medical Center. How metabolism really works.

  4. S Potgieter BScDietetics Mn. Sport nutrition: a review of the latest guidelines for exercise and sport nutrition from the american college of sport nutrition, the international olympic committee and the international society for sports nutritionSouth African Journal of Clinical Nutrition. 2013;26(1):6-16. doi:10.1080/16070658.2013.11734434

  5. USDA. Dietary Guidelines for Americans 2020–2025.

  6. USDA, Agricultural Research Service. Snacking associated with increased calories, decreased nutrients.

  7. Wilson MM, Reedy J, Krebs-Smith SM. American diet quality: where it is, where it is heading, and what it could beJournal of the Academy of Nutrition and Dietetics. 2016;116(2):302-310.e1. doi:10.1016/j.jand.2015.09.020

  8. American Heart Association. How can I eat more nutrient-dense foods?

  9. Clifton PM, Keogh JB. A systematic review of the effect of dietary saturated and polyunsaturated fat on heart disease. Nutrition, Metabolism and Cardiovascular Diseases. 2017;27(12):1060-1080. doi:10.1016/j.numecd.2017.10.010

  10. Pearlman M, Obert J, Casey L. The association between artificial sweeteners and obesityCurr Gastroenterol Rep. 2017;19(12):64. doi:10.1007/s11894-017-0602-9

  11. Academy of Nutrition and Dietetics. 4 keys to strength building and muscle mass.

  12. Rebello C, O'Neil C, Greenway F. Dietary fiber and satiety: The effects of oats on satietyNutr Rev. 2016;74(2):131-47. doi:10.1093/nutrit/nuv063

  13. Academy of Nutrition and Dietetics. 4 ways low-calorie diets can sabotage your health. Updated January 7, 2021.

  14. American Academy of Family Physicians. Healthy ways to gain weight if you're underweight.

  15. Iraki J, Fitschen P, Espinar S, Helms E. Nutrition recommendations for bodybuilders in the off-season: a narrative review. Sports (Basel). 2019;7(7):E154. doi:10.3390/sports7070154

  16. USDA FoodData Central. Bananas, ripe and slightly ripe, raw.

  17. USDA FoodData Central. Peanut butter, smooth style, with salt.

  18. USDA FoodData Central. Strawberries, raw.

  19. USDA FoodData Central. Ice creams, strawberry.

  20. American Cancer Society. Understanding food terms.

  21. Heiston EM, Gilbertson NM, Eichner NZM, Malin SK. A low-calorie diet with or without exercise reduces postprandial aortic waveform in females with obesityMed Sci Sports Exerc. 2021;53(4):796-803. doi:10.1249/MSS.0000000000002515

  22. Merra G, Gratteri S, de Lorenzo A, et al. Effects of very-low-calorie diet on body composition, metabolic state, and genes expression: a randomized double-blind placebo-controlled trialEur Rev Med Pharmacol Sci. 2017;21(2):329-345.

By Nicole M. LaMarco
Nicole M. LaMarco has 19 years of experience freelance writing for various publications. She researches and reads the latest peer-reviewed scientific studies and interviews subject matter experts. Her goal is to present that data to readers in an interesting and easy-to-understand way so they can make informed decisions about their health.