Final answer:
The author aims to highlight the potential inaccuracies in calorie listings on U.S. food labels due to the methods used for calculating energy content of foods, notably the Atwater system and bomb calorimetry, which may overlook factors like fiber.
Step-by-step explanation:
The author's purpose for writing about why most food labels are wrong about calories is to explain the inaccuracies in caloric content listed on U.S. food labels and provide insight into the methods used for calculating these values. The Atwater system is employed to derive the average caloric content of macronutrients—protein, carbohydrate, and fats—using bomb calorimetry data. However, this system may not account for various factors, such as the indigestible parts of food like fiber, thus leading to potential discrepancies between label information and the actual energy the body can use from the food.
Furthermore, food labels typically express energy content in Calories (or kilocalories), and understanding this can help consumers make informed decisions about their food choices based on nutritional labels. Misleading statistics regarding caloric content can affect one's ability to manage a healthy diet, as seen in the provided narrative about eating more cereal leading to healthy weight, suggesting the need for critical analysis of cause-and-effect claims in nutritional information.