Sorry for the late replies, been feeling quite down recently.
Vitamin B12 definitely has an effect on how food tastes. I got into the habit of drinking double bergamot earl grey tea because of it about a year ago. I used to take 1 mg of methylcobalamin sublingually every Sunday. But, somehow tolerance formed and the effect became weak. Taking it everyday just makes me tired and brain foggy with no noticeable benefits.
About 3 weeks ago I started taking Rhodiola at 500 mg, my usual dose, and this time it decreased my appetite even further. I was literally going an entire day without feeling hunger or just feeling it a little bit.
Really, my biggest problem is a lack of taste. Everything tastes bland. Pizza, fried chicken, cake, ice cream, etc, nothing has flavor. The anhedonia definitely is involved in this, but I've always had a low appetite, even when I was a kid.
Have you heard of nabilone? It's a synthetic cannabinoid used in cancer for treating nausea. There are a few anecdotes that say it increases appetite like THC. Maybe I can get a prescription for it? I would've liked to try THC, but here in Canada dronabinol was removed from the market by the pharmaceutical company that makes it.