1 and 1 calorie are the heat required to raise the temperature of 1 gram of water 1 degree Celsius at standard atmospheric pressure. Every gram of carbohydrate and protein contains 4 calories, and 1 gram of fat contains 9 calories. Combined with the mass of these three substances in food, the calorie value of food can be calculated.

2. Calculation method of food calories: Generally speaking, food is usually composed of carbohydrate, fat, protein and water, and water is not considered when calculating food calories. As long as we know the contents of the other three substances in food, and combine the calorie standards of these three substances, that is, 1 g carbohydrate contains 4 calories, 1 g protein contains 4 calories, and 1 g fat contains 9 calories, we can calculate how many calories the food contains.

3. Take100g of rice as an example. In100g of rice, there are 25.6g of carbohydrates, 2.6g of protein and 0.33g of fat. So the calorie of 100 gram of rice is equal to 25.6 times 4 plus 2.6 times 4 plus 0.33 times 9. The final result is about equal to 1 16 calories. 25.6 * 4+2.6 * 4+0.33 * 9 =115.77 kcal.