All life activities require energy to sustain them. The body's energy comes mainly from the three major energy-producing nutrients in food, including sugars (mainly carbohydrates), lipids (including fats, phospholipids, and steroids), and proteins. These three kinds of energy-producing nutrients and then oxidized in the human body to produce energy are: 1 gram of carbohydrates is equivalent to about 4 kilocalories (kcal), 1 gram of fat is equivalent to about 9 kilocalories (kcal), 1 gram of protein is equivalent to about 4 kilocalories (kcal).

Carbohydrates: Carbohydrates, also known as sugars, are the most abundant energy substance in nature.

Fats: Fats are the body's main source of energy and the most important body component and form of energy storage.

Protein: Protein is the material basis of all life. Every living thing, including animals and plants, every cell in the body is made up of proteins.

Calories are phonetically translated from the English word for card (calorie). Card (calorie, cal) is one of the units of energy used to be used in nutrition, the other is the kilocalorie (kcal). 1 kcal refers to 1 standard atmospheric pressure, 1 liter of pure water from 15 ° C to 16 ° C the energy required. Internationally used energy units are joule (J), kilojoule (kJ) and so on. The energy units in the Chinese food composition table are kilocalorie (kcal) and kilojoule (kJ), and the conversion relationship between them is: 1 kilocalorie (kcal) = 4.184 kilojoule (kJ). For example, 100 grams of rice has 486 kilojoules of energy, or 116 kilocalories (kcal).

As for calories, it's really just a common name for energy. It is worth mentioning that, regarding calories, some people also take it to refer to energy or calories, for example, some people will say, this piece of cake is very high in calories.