Welcome to Psych Central. There are particular things about Lithium that indicate the need not to be on "draconian diets"
psychcentral.com/blog/archives/2011/.../6-bipolar-rules-for-eating/

A low sodium diet is important
Psych Central Reviews - Lithium carbonate

Crash diets can exaggerate the effects of lithium
psychcentral.com/lib/medications-for-mania-and-manic.../2

Other articles are available - search box is in upper right hand corner of web pages linked to above.