Except PAM is not zero calories. It's just cooking oil in a sprayer can.
If used per the instructions, it can be legally labeled as "zero calories" if you use a one second spray or less, which is between five and ten calories of oil. If you press the sprayer any longer than one second, the amount of oil increases and so does the actual calories.
Dumb fats like Amber think that you can use any amount of PAM and there are no calories whatever added to what you're cooking, because they want to believe that a zero calorie cooking oil exists. It does not exist.