I have a can of high-quality nutritional yeast in the pantry. I only use it as an occasional treat/supplement for my pet rats, but I acquired a taste for it during a four-year stint as a vegan in the olden days and wouldn't mind using it again.
I gained weight when I quit drinking, dipping, and smoking last year, and only really cleaned up my diet in early August. I've lost 22 lbs since August 4, and am reintroducing benign (or not especially terrible) starches to slow my weight loss to a sane rate. I think the way I eat right now is coincidentally close to the Perfect Health Diet.
My reason for wanting to eat nutritional yeast is that it tastes good and is, um, nutritional. Is there any metabolic reason not to eat it? I have nothing against the "is it Paleo?" construct but I'm most concerned with whether there's an actual positive or negative effect on human metabolism - for instance, the yeast is doubtlessly cultured on some kind of sugar, but it's sugar-free itself, and I have no idea what the implications of that are. I also remember hearing that it contained something like an MSG analog.
I'm obviously not going to die if I don't eat it, but I'd like to have a compelling health reason not to eat tasty food in my pantry. Any input would be greatly appreciated.
The reason you might not want to eat a lot of yeast is that there is a lot of RNA in it. When nucleotides are digested, large amounts of uric acid are produced. It's really a very similar effect to the metabolism of fructose given that fructose causes a spike in the catabolism of adenine nucleotides (ATP->ADP->AMP->IMP->inosine->hypoxanthine->xanthine->uric acid).
Anyway, if you take a look at a paper like this one: http://www.ajcn.org/content/21/9/892.short You'll see that yeast really spikes uric acid levels. The reason why we don't want that is that elevated uric acid is principally why sugar causes insulin resistance, type II diabetes etc.: http://ajprenal.physiology.org/content/290/3/F625.short.
I don't know how much yeast it would take to simulate drinking a 2L bottle of cola a day, but if you're trying to improve insulin sensitivity, lose weight etc. it will definitely work against you.