Problem reducing Excel 2007 file size

[intuitiveanalyst]

A little bit of searching on the site didn't lead to an answer to our specific question. We have a largish 2007 xlsx from which we deleted large chunks of validation and formatting which were no longer needed. After a save (even a "save as" to a new file), the file size did not change! Any idea of what's going on here or what we could do to reduce the size of the file? Thanks in advance!