1, direct measurement method: it is to burn food with a special device and measure the heat released. This method is the most direct, but it is very troublesome and will hardly be used in actual production.

2. Calculation method for determining ingredients: In most foods, calories come from protein, fat and carbohydrates. These three food ingredients have an average calorie value. protein and carbohydrate are 4 kcal/g, and fat is 9 kcal/g. Dietary fiber in carbohydrate is more complicated. Generally, soluble dietary fiber is calculated at 2 kcal/g, while insoluble dietary fiber is not counted as calories.

Daily calorie requirement

1, the daily calories required by adults = the basic calories required for basic metabolism of human body+the calories required for physical activity+the calories required for digesting food.

2. Calories required for digesting food = 10% x (minimum calories required for basic metabolism of human body+calories required for physical activity).

The above content Baidu Encyclopedia-food calories