I don't know of such a spelling or of the term even, Bingley. I skimmed through the link and 'dietetic' seems to fit into that sentence. If it is a spelling variant, like aetiology, aether and the like, the answer must be in the root. What is the root for diet/ dietetics? Or, could the word be, dieretic? That also might(?) fit into the context. Am curious to hear more.