Google syntax, a question.

Hello, if I want to remove pages from the serp when searching google, can u pls tell me what syntax I need to use ? I thought its (-) sign, but I tried and its not working, maybe I'm putting it incorrectly, can u tell me what I have to type in google if I want to search for keyword "weight loss" and remove all the pages that contain the keyword "fast" in it.

Thanks

"weight loss" -fast