What are Calories Anyway?

What is a Calorie?

A calorie* is a unit of energy that is used to measure the amount of energy stored in food. One food calorie is the amount of energy (heat) it takes to raise the temperature of 1 kilogram of water 1.8°F (1°C).

* MORE SCIENCE: The Calories you see on food labels are actually kilocalories, and are also called food calories. One kilocalorie is equal to 1,000 calories. This is why food calories are listed as "Calories" with a capital C. One Calorie equal 4,184 joules of energy.

Your body needs food energy

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You need energy to survive – to breathe, move, pump blood and more! Your body gets this energy from food. The number of calories in a food item is a measure of how much potential energy that food has.

  • A gram of carbohydrates has 4 calories
  • A gram of protein has 4 calories
  • A gram of fat has 9 calories

Foods are a combination of these three building blocks. So if you know how many carbohydrates, fats and proteins are in a food, you can figure out how many calories, or how much energy, that food contains.

Here are some calorie and fat contents that may surprise you:

Food Serving* Calories Fat Grams
Peanut butter 2 Tablespoons 190 16
Cheddar cheese 1 slice 113 9
Granola 1 cup 270 8
Snickers Bar 1 bar 271 13.6
Cinnamon Toast Crunch Cereal ¾ Cup 130 2.8
McDonald's Cheeseburger 1 300 12
Chocolate syrup 2 Tablespoons 100 0
Sugar 2 Tablespoons 35 0
Coca-Cola 1 can 140 0

* NUTRITION TIP: These are the recommended serving sizes for the foods listed. The portions we eat are often much larger. Pay attention to the amounts you eat - are you eating the recommended serving sizes? Check out these pages about proper portions and smart snacking.

How Many Calories Do You Need?

How many calories does your body need to function well? That number is different for everyone. You may notice on the nutritional labels of foods you eat that the "percent daily values” are based on a 2,000 calorie diet. Your body might need more or less than 2,000 calories. Height, weight, gender, age and activity level all affect your caloric needs.

So what happens if you take in more or fewer calories than your body burns? If you have extra calories, your body stores those calories as fat to be used later. If you eat fewer calories than you need, you will get the extra calories by burning stored fat.

If I get the right amount of calories - does it matter what I eat?

What types of food you eat matters - although you may not gain any weight if you eat exactly the number of calories that you burn, that doesn't mean you body is getting everything it needs! You body needs more than energy - you also need things like vitamins, minerals and fiber from your food.

Complex carbohydrates and proteins are healthier sources of calories than fats and sugars, but our bodies need a certain amount of fat* to function properly. The U.S. Food and Drug Administration recommends that a maximum of 30 percent of our daily calories come from fat. So, if you eat 2,000 calories a day, that's a maximum of 600 calories from fat, or 67 grams of fat, per day. A variety of foods from each food group is best. Your body is also full of muscles that need to be used often to stay strong and get stronger.

* NUTRITION TIP: Some sources of fat are healthier than others. Unsaturated fats are the most healthy type and mostly come from plant oils like olive oil and peanut oil, and include the healthy Omega-3 fats that are found in foods like fish. Saturated fats are not very healthy and are usually solid at room-temperature and come from animals, like red meat and dairy products. Trans fats are processed fats that should be avoided.

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