No, nutritional yeast isn't brewer's yeast (which tastes NASTY). It's a condiment, mostly used by vegans, and some people say it tastes like parmesan cheese or something like that. I haven't tried it myself though, so I can't comment on the taste.
I guess if you wanted to try something to get your cat to eat, it would be worth a try. I don't know any reason cats shouldn't have it.
Nutritional Yeast can be bought at most health food stores . Yes it does have a " cheesy " taste .. I never tried it for my animals but I like it sprinkled on my veggies in place of loads of butter ..
There's a health food store on the other side of town that carries it. I don't know if I'll try it now, as my cats are (knock wood) eating okay, but for future reference...
I know this is an older thread but I wanted to respond. Nutritional yeast is sold at Whole foods. It is full of the vitamins B's and protein. It does indeed make food more palatable and comes in handy when switching your cats food , when cats have been sick and especially for older cats. Cats love it. My cats also get it as an occasional treat just sprinkled on a plate. I used to use Fortiflora when trying to entice a cat to eat. I like the yeast better because Fortiflora has animal digest in it ( yuck) Nutritional yeast is very healthy.