I think this is one of the crazier ones. It's just canola oil! It's the same as spreading that much canola oil on the surface, the spray is mainly convenient because it spreads it out evenly for you without you needing to contact the surface. But Pam gets to put "0g fat" and "For Fat Free Cooking" on the side of all their cans.

That might even be realistic if you are spraying a baking sheet - since you cover the whole thing. But if you are cooking pancakes and spray the pan after each one you get a lot of carbs.