First of all, popular science, calorie means: it is a unit of energy. Energy or heat of 1 calorie can raise the temperature of 1 gram of water at one atmospheric pressure 1 degree Celsius. We often associate calories with food, but in fact they apply to anything that contains energy.

Why do you want to mark it? In fact, it is easy to understand that the higher the calorie of food, the higher the energy. When the energy intake is always greater than the human needs, it will cause obesity, and obesity is positively related to the incidence of many cardiovascular and cerebrovascular diseases and cancer, which undoubtedly becomes a serious health hazard. Especially in the United States, the obesity rate of young people and adults is increasing year by year, and the obesity rate is basically the first in the world. In order to remind people, it is of reference value to mark the calories of food.

Well, in that case, let's show you the calorie content on the food label by the way.

In food packaging, the name of this project is called nutrient composition table. In China, as in the United States, most foods are labeled compulsorily, so I will take domestic labeling as an example to teach you how to know nutrition labeling.

The mandatory items on the nutrition label in China are: energy, protein, fat, carbohydrate and sodium. Among them, energy generally refers to the energy contained in such objects per 100g g, and the unit is kilojoule (kJ), 1 calorie =4. 182 joule (j). Similar to the picture below:

What do you think of nutrition labels? This picture is the label of a biscuit, so the energy of this biscuit is 2023 kJ per100g, and NRV% is the ratio of the nutrient content in food to the daily intake of this nutrient. In other words, I eat 500g biscuits every day, so my energy for one day can meet the demand. But don't go into the wrong area. Seven kinds of nutrient elements needed by human body: water, protein, carbohydrate, fat, vitamins, minerals and cellulose are indispensable. 500g biscuits are enough for one day's energy, but it can't meet the intake of protein and sodium. In fact, from the perspective of energy supply alone, KFC's chicken legs are definitely good. But its nutritional elements are too single, and other nutritional elements can't keep up. If you keep eating, you will be "malnourished".

So that's why we can't be picky about food, and our diet should be rich and varied.