3D model optimization for sculpting only pls

Hi folks, i was sculpting a highres mesh with blender and preparing it to move to my other software (3d Coat) to sculpt further details on it, then i have found out the OBJ file with no normals data is one third of the blend file in terms of size then i came to this conclusion maybe blender is constantly calculates useless data like normals etc while sculpting, it would be nice if there was an option to get rid of a mesh's useless data for heavy sculpting ...