Learning About Calories
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Learning About Calories

Reviewed by: Mary L. Gavin, MD

When people talk about the calories in food, what do they mean? A calorie is a unit of measurement — but it doesn't measure weight or length. A calorie is a unit of energy. When you hear something contains 100 calories, it's a way of describing how much energy your body could get from eating or drinking it.

Are Calories Bad for You?

Calories aren't bad for you. Your body needs calories for energy. But eating too many calories — and not burning enough of them off through activity — can lead to weight gain.

Most foods and drinks contain calories. Some foods, such as lettuce, contain few calories (1 cup of shredded lettuce has less than 10 calories). Other foods, like peanuts, contain a lot of calories (½ cup of peanuts has over 400 calories).

Some people watch their calories if they are trying to lose weight. Most kids don't need to do this, but all kids can benefit from eating a healthy, balanced diet that includes the right number of calories — not too many, not too few. But how do you know how many calories you need?

How Many Calories Do Kids Need?

Kids come in all sizes and each person's body burns energy (calories) at different rates, so there isn't one perfect number of calories that every kid should eat. But there is a recommended range for most kids between 6 and 12 years old: 1,600 to 2,200 per day, depending on how active they are. 

When they reach puberty, girls need more calories than before, but they tend to need fewer calories than boys. As boys enter puberty, they may need as many as 2,500 to 3,000 calories per day, especially if they are very active. But whether they are girls or boys, kids who are active and move around a lot need more calories than kids who don't.

If you eat more calories than you need, the body changes extra calories to fat. Too much fat can lead to being overweight and other health problems. Only your doctor can say if you are overweight, so check with him or her if you're concerned. And never go on a diet without talking to your doctor!.

High-calorie foods — such as sugary sodas, candy, and fast food — quickly add up to too many calories. Instead, eat a healthy, balanced diet. Exercising and playing are really important, too, because physical activity burns calories.

How the Body Uses Calories

Your body needs calories just to operate — to keep your heart beating and your lungs breathing. As a kid, your body also needs calories and nutrients from a variety of foods to grow and develop. And you burn off some calories without even thinking about it — by walking your dog or making your bed.

But it is a great idea to play and be active for an 1 hour or more every day. That means time spent playing sports, playing outside, or riding your bike. It all adds up. Being active every day keeps your body strong and can help you maintain a healthy weight.

Watching TV and playing video games won't burn many calories at all, which is why you should limit those activities to no more than 2 hours per day. A person burns only about 1 calorie per minute while watching TV, about the same as sleeping!

Reviewed by: Mary L. Gavin, MD
Date reviewed: June 2018