[Beaker]

That depends on the artifical sweetner. I think that the sweetner in Diet Coke is aspartame. It's full name is L-aspartyl-L-phenylalanine methyl ester. It's marketed under the name of Nutrasweet. Formula: C₁₄H₁₈N₂O₅. It looks like this:
Funky, huh?

[CindyDawg]

I really believe it mimics sugar and is an appetite stimulant.