Final answer:
The caloric value of a meal can be calculated by multiplying the amount of protein, carbohydrate, and fat by their respective Atwater factors, which are 4 calories per gram for proteins and carbohydrates and 9 calories per gram for fats, summing these to get the total calorie content.
Step-by-step explanation:
The method to calculate the caloric value of a food item or a meal is based on the Atwater factors, which involve the average caloric content of macronutrients such as proteins, carbohydrates, and fats. The procedure is simple: multiply the weight of each macronutrient by its respective caloric energy factor—4 calories per gram for proteins and carbohydrates, and 9 calories per gram for fats. If the carbohydrate content includes fiber, its amount is reduced since fiber is an indigestible carbohydrate. An example calculation for a 228-gram portion of food is (5 g protein x 4 Calories/g) + (31 g carb × 4 Calories/g) + (12 g fat × 9 Calories/g) = 252 Calories. The Atwater system is widely used because of its simplicity, yielding values that are close to those obtained using more complex methods like bomb calorimetry or indirect calorimetry.