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How Calories Work
You get energy from foods you eat, and you spend energy when you are active. Find out how to make this the key to losing weight.

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How Calories Work

In almost any weight-management plan, you'll find a mention of calories. You may think of these as friends or foes. But do you understand what they are, and what they mean to your goals?

A calorie is a unit of measurement. We hear about calories in relation to food, but they actually measure energy, not nutrients. Calories are to your body what fuel is to a car. You can't function without them.

Just as you use calories to measure the energy that foods give your body, they also are a measure of the energy you put out when you are physically active.

You are burning calories right now, as you're reading this article. You burn calories when you think, blink or smile. Your body is constantly at work using calories just to keep your blood flowing and your brain working.

To stay at your current weight, you need to consume just as many calories as you burn in a day. This is called a calorie balance. Each person's needs are different.

So it stands to reason that to lose weight, you need to burn more calories than you take in. You can do this by eating less (or eating more of better, lower-calorie foods!) and exercising more.

You can manage your calories the same way you manage your money: by using a budget. If you indulge at one meal, cut back at the next, or plan to exercise to work off the extra calories.

How you burn calories
The rate at which your body burns calories is called your metabolism. People can have a fast metabolism or a slow one.

Several factors contribute to how quickly your body burns calories. Here are a few:

  • Your body size. Bigger people burn more calories.
  • Your body composition. Lean muscle, even at rest, burns more calories than fat.
  • Your gender. Men, in general, have more lean muscle, so they burn calories at a higher rate than women.
  • Your age. Your metabolism slows as you age, so younger people burn calories faster.
  • Your family history. Genetics help determine your metabolism.

What can you do to help your body burn calories more quickly? Develop more lean muscle. Strength-training as little as twice a week can help you lose fat and build muscle. Using hand weights and/or resistance bands at home can be a good place to start.

Aerobic exercise - physical activity that gets your heart rate up - can also help you shed fat and build muscle. Aim for at least 30 minutes of moderate-intensity exercise most days of the week, with a minimum target of 2 hours and 30 minutes per week.

If you are physically inactive or have a chronic health condition such as arthritis, diabetes or heart disease, check with your doctor before starting an exercise program. He or she can tell you what types and amounts of activities are safe and suitable for you.

Balancing calories in and out
It's important to know how many calories you're taking in and how many calories you're using while being physically active. There are several ways you can do this. Here are a few:

  • Read nutrition labels. Most foods are required to have a packaging label that lists calories.
  • Know the calories of your favorite foods. A great resource is the United States Department of Agriculture's calorie counter.
  • Keep a food journal. Write down everything you eat and drink. This includes snacks. Jot down the calories and keep a running total throughout the day. Everything counts!
  • Keep track of your exercise. Record any exercise you've done and the approximate calories you burned.

Calorie-counting is one of many tools that may help you pay more attention to the foods you eat and the exercise you're getting. It's one more step in the journey.

By Ginny Greene, Editor
Created on 02/25/2013
Updated on 02/25/2013
  • Centers for Disease Control and Prevention. Balancing calories.
  • Centers for Disease Control and Prevention. Healthy weight – it’s not a diet, it’s a lifestyle!
  • United States Department of Agriculture. Dietary guidelines for Americans 2010.
  • Academy of Nutrition and Dietetics. Metabolism myths and facts.
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