At what point after swallowing does food become a calorie?

Before you swallowed the food, it contained a number of calories or what we call potential energy measured in calories. Not until the food is broken down in your digestive tract and then absorbed into the body does it become something your body can use for energy. So - it becomes a useful calorie to your body after absorption. And almost all food you eat gets absorbed, so you can pretty much count the calories from the food you eat as the calories in your body