Final answer:
Protein and carbohydrates both provide about 4 calories per gram, whereas fats provide about 9 calories per gram. These calorie values are used in determining the nutritional content of food items and are calculated using the Atwater system based on bomb calorimetry of whole foods.
Step-by-step explanation:
From proteins, fats, and carbohydrates, the human body derives different amounts of calories per gram. Each gram of protein provides approximately 4 calories, similar to carbohydrates, which also provide about 4 calories per gram. In contrast, fats are more calorie-dense, offering about 9 calories per gram. This information is critical for understanding nutritional labels on food packages, which show the caloric content and breakdown by these macronutrients. The Atwater system is commonly used today to derive the caloric content on these labels, utilizing average caloric values obtained from bomb calorimetry experiments on whole foods.