Or is it all just one big lie?
Credit: Roberto Machado Noa/ Getty

Turn to the nutrition label on your can of cooking spray and you might be surprised to see that there are zero calories in a serving. But, lots of other “diet” products, like diet soda, have zero calories due to artificial flavors and sweeteners. So is it really surprising? Well, actually, yes.

Skim the ingredient list of common brands like PAM original or PAM butter flavor, and the first three ingredients are canola oil, palm oil, and coconut oil. Similarly, Costco’s Kirkland brand sells canola oil spray, and the first ingredient is actually canola oil. There are no artificial ingredients in sight, but the numbers still don’t add up. How does a product claiming to use real oil have zero calories?

We turned to math (and our test kitchen) to find the answer. Turns out, most cooking sprays’ nutrition labels use the serving size of about one-third of a second to calculate calories. I don’t know about you, but I definitely take more than one-third of a second to spray my pans. In reality, there are about eight calories for every one-second spray.

So, how many calories are you really consuming when you spray a pan? We tested and timed spraying a 13-x-9-inch glass pan, 9-inch square glass pan, and a 9-inch metal cake pan to see how long it really took to coat each one. After a few rounds, we estimated most pans take three to four seconds to adequately spray for non-stick cooking. This ends up being about 30 calories in a four second spray. Not so "zero calorie" anymore, is it?

Despite the nutrition label skewing a realistic serving size, we still think using cooking spray to cut down on calories is a good idea. One teaspoon of canola oil provides about 41 calories, so you’re still keeping your calorie count down if you don’t go overboard on the spraying. Stick to spraying pans for less than five seconds, which is about 38 calories, if you’re looking to cut calories from traditional oil.