Sure, you've checked the number of calories in a sports bar or fruit smoothie. You've heard the diet commercials blab about cutting calories. But what exactly is a calorie?

A calorie is a unit that measures the amount of energy in your body. The source of that energy is everything you eat and drink. Your body uses that energy all the time. Even when you're asleep. Calories provide the fuel you need for every physical activity. That includes your body's metabolic functions like breathing (respiration) and the movement of blood through your veins and arteries (circulation). back to top

How many calories are enough?
Your daily calorie requirement depends on your age, your body size, your lean body mass, and your activity level. Girls and boys have different calorie needs too. Click here to find out how many calories a day you need. back to top

How many calories are in a pretzel?
Check the label! A Nutrition Facts label appears on most processed and some raw foods, like baby carrots and eggs. The label tells you how many calories a particular food contains per serving. A serving may be two pretzels even though the package holds 10—so read the label carefully. back to top

What foods have the most calories?
Foods are made up of nutrients that usually contain calories. Fat is the biggest supplier, providing a whopping nine calories in each gram. Butter and all kinds of oils are fats. Carbohydrates and proteins add four calories per gram. Cereal, rice, bananas, and orange juice are all examples of carbohydrates . Proteins include chicken, soy products like tofu, and nuts. Water is found in almost everything you eat or drink. It has no calories. back to top

Is low fat the same as low calorie?
Check those Nutrition Facts labels! Many low fat foods are high in calories from other nutrients. But just because a food is high in calories doesn't mean that it will make you gain weight. It simply means that it contains more units of energy than a food with fewer calories. Check the calorie count of your favorite foods. back to top

Burning 'em up
When your body uses food as fuel, it is said to "burn calories." The number of calories you burn depends on your weight, how often you exercise (frequency), how long you exercise (duration), and how hard you exercise (intensity ). Regular exercise can even increase your ability to burn calories while you rest. The more lean body mass you have, the more calories your body burns. back to top