Final answer:
The calories in one serving of a product can be found on the food label, usually in terms of kcal, which is equivalent to Calories as used in the U.S. The caloric content is determined by bomb calorimetry, which measures the energy in food when burned.
Step-by-step explanation:
To determine how many calories are in one serving of a product, it's essential to first look at the food label. The label provides you with the serving size and the calorie content per serving. For instance, the label may state that one cup of food is a serving and there are 250 calories per serving. To ensure accurate tracking of your calorie intake, you can use food labels. You might also find it useful to know how these caloric values are derived. Foods are tested using bomb calorimetry, where the food is burned and the energy content measured. This method determines the calories in terms of the energy released per gram of food.
If an athlete, for example, were to metabolize 500 kcal of food energy with an efficiency of 20%, they would be using calories efficiently to do work, as opposed to storing it as fat.