You can try the following tool
http://www.mathworks.com/matlabcentral/fileexchange/45749-clean-anonymous-functions-of-excess-memory
but read the disclaimers.
Anonymous/nested functions can only slow things down when you try to export handles to them from the workspace where they were created. Either you're returning the handle from a function, saving it to a .mat file, or sending it to a parfor worker.
