What Do Calories Mean in Food and Exercise?

Definition of Calories for Eating and Burning Them

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A calorie is a measure of energy expenditure and stored energy. The calories referred to in diet (calories eaten) and exercise (calories burned) are kilocalories (kcal). One kilocalorie is equal to the amount of heat that will raise the temperature of one kilogram of water by one degree Celsius at sea level. One kilocalorie is equal to 4186.8 joules and 1000 calories (small calories) referred to in science labs for heat energy.

  • Pronunciation: cal er ee
  • Common Misspellings: calourie, calory
  • Examples: I will walk for 3.5 miles to burn off the calories in that Snickers bar.

Calories in Food

Calories in food are grouped as fats, alcohol, carbohydrates or proteins. Different nutrients have more or fewer calories packed into the same weight (higher or lower calorie density). Nutrition labels in the US use these rules of thumb:

  • 1 gram of fat has 9 calories (kcal)
  • 1 gram of alcohol has 7 calories (kcal)
  • 1 gram of protein has 4 calories (kcal)
  • 1 gram of carbohydrate (sugars and starches) has 4 calories (kcal)

Calories and Weight Loss

A pound of body fat stores 3500 calories (kcal).

To lose a pound of fat in a week, a person must eat approximately 500 fewer calories (kcal) per day than he/she expends in metabolism and exercise.

The number of calories that a person burns each day includes basal metabolic rate calories burned just to keep the body functioning, plus additional calories burned in physical activity.

The range of daily calorie burning is from 1600 calories (kcal) for a sedentary woman or for an older person to 2800 calories (kcal) for active men, very active women and teenage boys.

Calories per Day Calculator: Find how many calories you burn each day based on your height, weight, age, and activity level.

Using a fitness monitor and app to track calories eaten vs. calories burned can assist dieters who want to achieve a calorie deficit to lose weight. Tracking activity with a fitness monitor helps eliminate overestimates on the side of calories burned, while honest tracking of what is eaten can highlight where food calories are coming in.

Calories Burned in Physical Activity

Physical activity burns calories beyond the basal metabolic rate as muscles use available and stored energy sources in the body. Depending on the duration and intensity of exercise, the body burns available blood sugar, glycogen stored in the muscles and liver, fat and, if required, muscle protein.

  • Exercise Calorie Calculator: Enter your weight and minutes spent exercising in a variety of physical activities at moderate intensity.
  • Walking Calorie Calculator: find out how many calories you can burn per mile based on your weight and speed. Walking burns approximately 100 calories per mile for a 150 pound person.
  • Fat-Burning Zone: When exercising at 60-70% of your maximum heart rate, 85% of the calories you burn are from fat.

Measuring Calories Burned

Fitness monitors and pedometers often estimate calories burned based on the weight of the person, number of steps taken, speed, pace and intensity.

Some use heart rate monitors to get a better estimate of physical activity.

View Article Sources
  • Finding a Balance, Centers for Disease Control, Division of Nutrition, Physical Activity, and Obesity, National Center for Chronic Disease Prevention and Health Promotion. Updated May 15, 2015. Accessed October 3, 2015.
  • Endurance Sports Nutrition, Third Edition by Suzanne Girard Eberle.Human Kinetics, 2014.