Erm...<question word="">も~ない and <question>でも~ない have slightly different meanings.
E.g: �*れもいない dare mo inai - There is no-one
�*れでもいない daredemo inai - There isn't anyone
Basically just use whichever sounds more natural
なにもたべたくない nani mo tabetakunai
なんでもたべたくない nandemo tabetakunai
In this case the 2nd would be better to use (I don't want to eat anything) as opposed to (I want to eat nothing).</question></question>