Counting Calories

This falls into the category of "close enough as makes no difference." Yes, if you deep fat fry and leave most of the oil in the pan, not all the oil counts because you are not consuming it. Weighing before and after won't really give you very useful figures on how much oil you consumed because juices also move around and water evaporates. When sautéing, you may leave some oil behind but how to determine how much is a crap shoot. Some foods change the amount of available calories after cooking. Some go up, others go down.

Our calorie counts for foods are a best guess based to some degree on relatively old "bomb calorimetry" measures that repeatedly get included without change or correction because it's hard to do bomb calorimetry. Manufacturers use the same USDA legacy database we do to figure out calories and rely on those same old bomb calorimetry figures to add up calories in recipes.

Look at it like good weather forecasts and weather reports. They are close enough to decide what to wear and if you pay attention to them, whether you need rain gear. They are not perfect but "close enough" so we follow them.