Final answer:
To determine the percentage of calories from fat in John's lunch, we calculate the calories from each macronutrient and then find the fraction of the total calories that come from fat. With 25 grams of fat at 9 calories per gram, and the total meal being 869 calories, about 25.9% of the calories in John's lunch come from fat.
Step-by-step explanation:
To determine the percentage of calories from fat in John's lunch, we need to calculate the total calories provided by each macronutrient and then find out what fraction of the total comes from fat. Since fats provide an average of 9 calories per gram, proteins provide 4 calories per gram, and carbohydrates also provide 4 calories per gram, we can perform the following calculations:
Calories from CHO (carbohydrates) = 121 grams × 4 calories/gram = 484 calories
Calories from protein = 40 grams × 4 calories/gram = 160 calories
Calories from fat = 25 grams × 9 calories/gram = 225 calories
Next, we calculate the total calories in the meal:
Total calories in John's lunch = Calories from CHO + Calories from protein + Calories from fat
Total calories in John's lunch = 484 + 160 + 225 = 869 calories
Finally, we calculate the percentage of calories from fat:
Percentage of calories from fat = (Calories from fat / Total calories) × 100
Percentage of calories from fat = (225 / 869) × 100 ≈ 25.9%
Therefore, approximately 25.9% of the calories in John's lunch come from fat.