If minor or little changes in your excel workbook bloated its size to 200% and above then it's a serious issue but not worry issue as it has solution.
Understand the problem: First understand the difference between 'Excel Default Last Cell' and 'Actual Last Cell'. When you do 'Ctrl+End' to find last cell, you'll reach to 'Excel Default Last Cell' which may be the 'Actual Last Cell' or beyond the 'Actual Last Cell'. The more beyond 'Excel Default Last Cell' would be from 'Actual Last Cell', the more unnecessary size of excel workbook would it be having.
Solution: Delete all rows and columns beyond the 'Actual Last Cell' in every worksheet. If there are too many worksheets and large sets of data, you can use the VBA macro mentioned on eXceLiTems.com.
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