Too good to be true?

I discovered a new product at the store a couple of days ago. Well, the product may not be new, but it's new to me.

I was intrigued by the "no trans fat" label, and also by the fact that it was on sale for $1. I decided to investigate the nutritional label. Not only does this product have no trans fat, it has no calories. I can't figure out why they didn't say that in big letters on the front! Why are they making such a big deal about the trans fat? Needless to say, I bought the product.

Anyhow, upon further reflection, I can't figure out this butter spray. I have fully accepted that some things that taste like sugar can be calorie free. I think it's magic. But butter spray? That includes actual buttermilk? How does that even work? Are they just saying it has no calories because the serving size is "five sprays"? Am I going to get cancer after substituting this for butter for the rest of my life?