What are calories?
Most people only associate calories with food and drink, but anything that contains energy has calories. 1 kilogram (kg) of coal, for example, contains 7,000,000 calories.
There are two types of calorie:
- A small calorie (cal) is the amount of energy required to raise the temperature of 1 gram (g) of water by 1º Celsius (º C).
- A large calorie (kcal) is the amount of energy required to raise 1 kilogram (kg) of water by 1º C. It is also known as a kilocalorie.
1 kcal is equal to 1,000 cal.
The terms “large calorie” and “small calorie” are often used interchangeably. This is misleading. The calorie content described on food labels refers to kilocalories. A 250-calorie chocolate bar actually contains 250,000 calories.
The United States government states that the average man needs 2,700 kcal per day and the average woman needs 2,200 kcal per day.
Not everybody needs the same number of calories each day. People have different metabolisms that burn energy at different rates, and some people have more active lifestyles than others.
The recommended intake of calories per day depends on several factors, including:
- overall general health
- physical activity demands
- body shape
Here is a more detailed breakdown from the U.S. Department of Agriculture (USDA) on how many calories are needed for different body types.
Calories and health
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
- 1 g of protein contains 4 kcal
- 1 g of fat contains 9 kcal
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
Protein: 30.52 g
30.52 x 4 kcal = 122.08 kcal
Carbohydrate: 1.75 g
1.75 x 4 kcal = 7 kcal
243 g of raw egg contains 347 kcal. 208 kcal comes from fat, 122 kcal is taken from protein, and carbohydrate provides 7 kcal.
Fast food in American diets
Researchers from the Centers for Disease Control and Prevention (CDC) published a report in 2013 showing that 11.3 percent of calories consumed by people in the U.S. come from fast foods.
Nutritionists and healthcare professionals say this figure is too high.
As people get older, they tend to get fewer of their daily calories from fast foods. Fast foods make up only 6 percent of the daily calorie intake of older adults.
However, with the number of highly calorific meals served in restaurants or aimed at younger individuals, it is important that people pay close attention to where they get their calories.
When should you eat?
The time of day at which a person eats can shape how effectively their body uses calories.
A hearty breakfast can help the body to use calories more effectively.
Researchers at Tel Aviv University wrote in the journal Obesity that a large breakfast containing approximately 700 kcal is ideal for losing weight and lowering the risk of diabetes, heart disease, and high cholesterol.
A large breakfast may help to control body weight. When people eat matters as much as what they eat.
Empty calories are those that provide energy but very little nutritional value. The parts of food that provide empty calories contain virtually no dietary fiber, amino acids, antioxidants, dietary minerals, or vitamins. Empty calories come mainly from solid fats and added sugars.
- Solid fats: Although these exist naturally in many foods, they are often added during industrial food processing, as well as during the preparation of certain foods. Butter is an example of a solid fat.
- Added sugars: These are sweeteners that are added to foods and beverages during industrial processing. They are filled with calories. In the U.S., the most common types of added sugars are sucrose and high-fructose corn syrup.
Added sugars and solid fats are said to make foods and drinks more enjoyable. However, they also add many calories and are major contributors to obesity.
Alcohol can also contribute empty calories to the diet. One normal serving of beer can add 153 kcal to a person’s intake for the day.