Some times, when you move sheets from different file, the file size will be too large even though the contents of the file are very less.
The reason for this may be the Names defined in the original file which is moved to new file. These Names may not be required in this file and if the link for the defined Name is linked to sheet which is not moved, it will be of no use and it will show the error in name manager.
To remove these Names, you can go to Name Manager and filter the Names with error and delete the Names.
This will reduce the file size.