PDF Form increases in size 167.23KB - 5MB

I created interactive dynamic form using Adobe LiveCycle Designer ES 9.0.  I have this form set up to submit a PDF via email.  The initial size of the form is 167.23KB but I have found on several occasions that once the end-users begins using the form the file size increase to 3-5MB.  There are many versions of Acrobat being used by the end-users to view and submit the forms. Any help on this would be much appreciated.