What are calories?

Definition of Calories
Calories are a fundamental concept in nutrition, yet they're often misunderstood or oversimplified. At their core, a calorie is a unit of energy. It measures the amount of energy your body can get from the foods and beverages you consume. This energy is essential—it powers everything from breathing and thinking to walking and exercising.

The Scientific Definition
Scientifically, one calorie is the amount of energy needed to raise the temperature of one gram of water by one degree Celsius. However, when we talk about food calories, we’re actually referring to kilocalories (kcal). One food calorie (with a capital "C") is equal to 1,000 small calories (cal). So when a nutrition label says something has 200 calories, it means 200 kilocalories.

Why Calories Matter
Your body needs calories to function properly. Every cell in your body relies on energy to operate. Even when you're at rest, your body is burning calories to maintain your heartbeat, brain activity, digestion, and more. This is known as your basal metabolic rate (BMR)—the minimum number of calories your body needs to survive.

Calories also come into play when it comes to weight management. If you consume more calories than your body uses, the excess energy is stored as fat. On the other hand, if you burn more calories than you take in, your body uses stored fat for energy, leading to weight loss. This balance of calories in vs. calories out is at the heart of most diet and fitness strategies.

Where Do Calories Come From?
Calories come from three main macronutrients: Carbohydrates: 4 calories per gram
Proteins: 4 calories per gram
Fats: 9 calories per gram

Alcohol also provides calories—about 7 per gram—but it's not considered a nutrient because it doesn’t provide essential functions for the body.

How Many Calories Do You Need?

Knowing how many calories your body needs each day is a key step toward better health, whether your goal is to maintain weight, lose fat, or build muscle. The number of calories you require depends on several factors, including age, gender, weight, height, activity level, and overall health.

Average Daily Calorie Needs
While everyone’s body is different, here are some general guidelines provided by health experts:

Average adult woman:
About 1,800 to 2,200 calories per day to maintain weight, depending on physical activity.
Sedentary women need fewer calories, while active women may need more.

Average adult man:
About 2,200 to 2,800 calories per day to maintain weight, again depending on activity level.
Active men, especially those with larger body frames or muscle mass, often require more energy.

These are only estimates and may not reflect your individual needs. Factors like metabolism, muscle mass, and daily routines can have a significant impact on your actual calorie requirements.

Let Our Calorie Calculator Help
Instead of guessing, you can use our Calorie Calculator to get a more personalized and accurate estimate. Just enter your basic info—such as age, gender, height, weight, and activity level—and we’ll calculate how many calories your body needs to:

Maintain your current weight
Lose weight safely
Gain lean muscle mass

Our tool makes it easy to tailor your nutrition to your goals, whether you're just getting started or fine-tuning your current routine.

What Do Calories in Food Mean?

When you see the word calories on a food label, you're looking at a measure of how much energy that food provides your body. Simply put, calories are the fuel that keeps your body running—just like gas powers a car.

Every time you eat or drink something, you're taking in energy. Your body then uses that energy to perform all kinds of functions, from essential ones like breathing and circulating blood to physical activities like walking, working out, or even just sitting and thinking.
Not All Calories Are Equal
While the number of calories tells you how much energy a food provides, it doesn’t say anything about nutritional quality. For example, a soda and a handful of nuts might contain a similar number of calories, but your body reacts to them in very different ways. Foods rich in vitamins, minerals, fiber, and healthy fats support your overall well-being, while "empty calories" (like those from sugar and processed snacks) may leave you feeling unsatisfied and low on nutrients.

Understanding what calories in food mean can help you make smarter, more balanced choices—fueling your body in a way that supports your goals and long-term health.

Lose Weight

What Do Calories Have to Do with Weight Gain or Weight Loss?

Calories play a central role when it comes to managing your weight. Whether you’re trying to lose weight, gain weight, or maintain your current size, it all comes down to calories in vs. calories out—a simple concept with a big impact.

The Calorie Balance Equation
Your body needs a certain number of calories each day to function—this is known as your maintenance level. When you eat more calories than your body burns, the extra energy is stored as fat, leading to weight gain. On the flip side, if you consume fewer calories than your body needs, your body turns to stored fat for energy, resulting in weight loss.

Small Changes, Big Results
You don’t need to make extreme changes to see progress. A small daily calorie deficit - like eating 250 fewer calories or burning 250 extra calories through exercise—can lead to gradual, healthy weight loss over time. Similarly, eating just a few hundred extra calories a day can lead to weight gain if it becomes a consistent habit.

Quality Still Matters
While calorie quantity affects your weight, the quality of your calories affects how you feel and how your body responds. Whole, nutrient-rich foods help keep you full and energized, while processed foods high in sugar and fat can lead to cravings and overeating—even if the calorie count seems low.

What are empty calories?

Empty calories are calories that provide energy but offer little to no nutritional value. They typically come from foods and drinks that are high in added sugars and unhealthy fats, but low in essential nutrients like vitamins, minerals, fiber, or protein.

Where Do Empty Calories Come From?

Common sources of empty calories include:
Sugary drinks (soda, energy drinks, sweetened coffee)
- Candy and sweets
- Baked goods made with refined flour and sugar
- Fried foods
- Fast food
- Alcohol

While these foods can give you a quick energy boost, they don’t support your body’s long-term health needs. In fact, relying too heavily on empty calories can lead to weight gain, low energy, and nutrient deficiencies—especially if they replace more nutritious options in your diet.

Do Empty Calories Have a Place in a Healthy Diet?
In small amounts, empty calories can fit into a balanced lifestyle—especially if the rest of your diet is rich in whole, nutrient-dense foods. The key is moderation. Treats are okay occasionally, but your daily calorie intake should mostly come from foods that fuel your body with the nutrients it needs to function at its best.

Which Foods Are High in Calories?

Some foods naturally contain more calories because they’re high in fat, sugar, or both. Common high-calorie foods include:

1. Fast food (burgers, fries, fried chicken)
2. Sweets and desserts (cakes, cookies, chocolate)
3. Nuts and nut butters (like almonds or peanut butter)
4. Cheese and full-fat dairy products
5. Processed snacks (chips, crackers)
6. Sugary drinks and alcohol