In the case related to this solution, the image being used was a 27 by 20 JPEG at 72 dpi. It was imported in a box with the size 1.1 by 1.1. This resulted in too much pixel data information being captured into a small picture box. QuarkXPress will always try to embed all the information for any image below 96 dpi.
There are other things you can do to reduce project files size. The default preview bit depth set in the QuarkXPress Preference > Display pane are set for the highest bit depth. if you reduce the bit depth for Color TIFF and Grayscale TIFF preview displays, the file size for QuarkXPress projects will be significantly reduced.
If you require high resolution images for printing, resave the image at 300 dpi (or slightly higher as advised by your print service provider) without altering any other information. Then re-import the images. This will result in a reduction of QuarkXPress Project size. QuarkXPress and QuarkXPress Server will then generate the preview and provide high resolution image output only when requested in the output specifications.
QuarkXPress automatically displays a low-resolution 72 dpi preview of each imported picture file while maintaining a path to picture files and retrieving the high-resolution information required for output. QuarkXPress uses two types of information for imported pictures: low-resolution and high-resolution. Low-resolution information is used to display picture previews. When you print, high-resolution information contained in the original picture files is accessed using paths to the pictures. Path to a picture is established when you import a picture. The application keeps information about each picture's path as well as when the picture was last modified.