Final answer:
To calculate calories from carbs, proteins, and fats per serving, multiply the grams of each macronutrient by their respective calories per gram (4 for protein and carbs, 9 for fats), then sum the results to get the total calories per serving.
Step-by-step explanation:
Calculating Calories from Macronutrients
To calculate the number of calories from carbs, proteins, and fats per serving, you can use the average caloric content values known as the Atwater system. For proteins and carbohydrates, you multiply the number of grams per serving by 4 calories per gram. For fats, you multiply the grams per serving by 9 calories per gram. The resulting values represent the calories from each macronutrient, which are then summed to obtain the total caloric content of the serving. For example, a serving with 5 grams of protein, 31 grams of carbohydrates, and 12 grams of fat would have a total energy content of:
- (5 g protein x 4 calories/g) = 20 calories from protein
- (31 g carb x 4 calories/g) = 124 calories from carbohydrates
- (12 g fat x 9 calories/g) = 108 calories from fat
By adding these values together (20 + 124 + 108), the total calories per serving would be 252 calories.