Do I need a new key if I lost the fob?

I lost the key fob for my 2001 Buick Century, I found a replacement one online but my question is do I need a new key for the new fob to work?According to amazingkeys.com you just need the remote and the included programming instructions for your 2001 Buick Century. Here is the link to the remote and the programming: http://www.amazingkeys.com/product/2001-01-buick-century-remote-keyless-key-entry-clicker-oem-sp