A calorie is a unit of energy. In nutrition, calories refer to the energy people get from the food and drinks they consume and the energy they use in physical activity.
Calories are in the nutritional information on all food packaging. Many weight loss programs involve reducing calories.
This MNT Knowledge Center article focuses on calories associated with food and drink and how the human body uses energy. MNT covers what a calorie is, how many calories humans need each day, and how to get calories in a way that benefits overall health.
Fast facts on calories
- Calories are essential for human health. The key is consuming the right amount.
- Everyone requires different amounts of energy each day, depending on age, sex, size, and activity level.
- Foods high in energy but low in nutritional value provide empty calories.
Most people associate calories only with food and drink, but anything that contains energy has calories. For example, 1 kilogram (kg) of coal contains 7,000,000 calories, or 7,000 kilocalories.
There are
- A small calorie (cal) is the amount of energy required to raise the temperature of 1 gram (g) of water by 1ºC.
- A large calorie (kcal or Cal) is the amount of energy required to raise 1 kilogram (kg) of water by 1ºC. It is also known as a kilocalorie.
This means 1 kcal is equal to 1,000 cal.
However, the terms “large calorie” and “small calorie” are used interchangeably, which can be misleading. The calorie content described on food labels refers to kilocalories. A 250-calorie chocolate bar contains 250,000 calories.
The current
Not everybody needs the same number of calories each day. People have different metabolisms that burn energy at different rates, and some have more active lifestyles than others.
The recommended intake of calories per day depends on several factors, including:
- overall general health
- physical activity demands
- sex
- weight
- height
- body shape
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 necessary 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 it contains. However, while total calories are important, the source of the calories is also important.
Below are the calorific values of the 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
While being mindful of caloric intake
When should a person eat?
The time of day a person eats can shape how effectively the body uses calories and may matter as much as what they eat.
Although more research is necessary to confirm, there is some evidence that a large breakfast or morning eating may help manage body weight.
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.
According to ChooseMyPlate.gov, a diet management tool from the USDA, empty calories come mainly from solid fats and added sugars.
- Solid fats: Although these exist naturally in many foods, they are also added during industrial food processing and 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 highly calorific. In the United States, the most common types of added sugars are sucrose and high fructose corn syrup.
Added sugars and solid fats make foods and drinks more enjoyable. However, they also add many calories and are major contributors to obesity.
For alcohol, a person can use this
Sources of empty calories
The following foods and drinks may provide the largest amounts of empty calories:
- ice cream
- donuts
- cookies
- cakes
- bacon
- hot dogs
- sausages
- fruit drinks
- sports and energy drinks
- regular soda
The leading source of empty calories in the United States
More than half of all people in the United States have at least one sugary drink each day.
There are ways of sourcing products with less solid fat or empty sugars. Rather than choosing the standard hot dog or cheese, for example, a person could choose low fat options for either.
However, even the lower fat options are no replacement for calories consumed from sources that also provide nutritional benefits. Rachel Johnson, a spokesperson for the American Heart Association (AHA), shared the following with MNT:
“Sugar-sweetened beverages are the number one single source of calories in the American diet and account for about half of all added sugars that people consume.
“It’s better if you can avoid them altogether and instead consume water, fat-free or 1 percent fat milk, 100 percent fruit juice, and low sodium vegetable juices.”
Incorporating fresh, nutritious food and drinks into the diet can help a person avoid or dramatically reduce empty calories.
How can a person calculate how many calories they need?
A person can use the calorie calculator app to find out how many calories they need in terms of age, weight, and sex.
How many calories should a person eat to lose weight?
Maintaining a calorie deficit of 500 to 600 calories per day can help a person lose weight.
Calories may link to weight gain and obesity, but they are vital for health. They only pose a health risk when people consume more than the recommended amount.
When considering calories, it is best to consider diet and level of physical activity. A person can counter a high intake of calories with regular, high intensity exercise.
