Creating a buffer based on area (i.e. sqm) instead of distance

Question

Is there a way in ArcGIS 10.1 or QGIS (or any add-on) to create buffer based on an area (i.e. sqm) rather than using buffer distance? I'd like to create a buffer of let's say 5% of the area within the buffer. The problem is that the feature is not regularly shaped. Thanks, Alex