CALORIES
A calorie is a unit of energy. In nutrition, calories refer to the energy people get from the food and drink they consume, and the energy they use in physical activity.Calories are essential for human health. The key is consuming the right amount.Everyone requires different amounts of energy each day, depending on age, size, and activity level.Foods high in energy but low in nutritional value provide empty calories.
The human body needs calories to survive. Without energy, the cells in the body would die, the heart and lungs would stop, and the organs would not be able to carry out the basic processes needed for living. People absorb this energy from food and drink.
If people consumed only the number of calories needed every day, they would probably have healthy lives. Calorie consumption that is too low or too high will eventually lead to health problems.
The number of calories in food tells us how much potential energy they contain. It is not only calories that are important, but also the substance from which the calories are taken.
Below are the calorific values of three main components of food:
- 1 g of carbohydrates contains 4 kcal(calories)
- 1 g of protein contains 4 kcal(calories)
- 1 g of fat contains 9 kcal(calories)
As an example, here is the breakdown of how a person would get calories from one cup of large eggs, weighing 243 g:
Fat: 23.11 g
23.11 g x 9 kcal = 207.99 kcal(calories)
Protein: 30.52 g
30.52 x 4 kcal = 122.08 kcal(calories)
Carbohydrate: 1.75 g
1.75 x 4 kcal = 7 kcal(calories)
243 g of raw egg contains 347 kcal. 208 kcal comes from fat, 122 kcal is taken from protein, and carbohydrate provides 7 kcal.
Calories Burned in Physical Activity
Physical activity burns calories beyond the basal metabolic rate. Your muscles use both readily available and stored energy sources in your body.
The exercise calories burned during cardiovascular activities such as walking, running, swimming, and cycling depend on the intensity of the exercise, your body weight, and the amount of time you spend exercising. Moderate-intensity exercises such as brisk walking burn fewer calories per minute than more vigorous-intensity exercises such as running. For example, you can use a walking calorie chart to find out how many calories you can burn per mile based on your weight and speed. Walking burns approximately 90 calories per mile for a 160-pound person.
Depending on the duration and intensity of exercise, your body burns available blood sugar, glycogen stored in the muscles and liver, fat and, if required, even begins to burn muscle protein. If you want to burn body fat, aim for exercising at 60 to 70 percent of your maximum heart rate for at least 45 minutes. In that fat-burning zone, 85 percent of the calories you burn are from fat. But you must first expend the more easily-available energy sources before your body turns to the fat stores.
Fitness monitors and pedometers often estimate calories burned based on your weight, number of steps taken, speed, pace, and intensity. It is generally more accurate if the exercise intensity is measured by the heart rate during exercise. You may use handgrip pulse monitors on a treadmill or elliptical trainer for a more accurate estimate. More and more fitness bands and smartwatches have pulse detectors built in to monitor your exercise intensity. A chest strap heart rate monitor is considered the most accurate.
