Heroin is an extremely dangerous drug that kills many people every day. I would not recommend using it, even if it does increase appetite.
I suffered from addiction years ago, and although I never became addicted to heroin, I tried it several times, and it never increased my appetite, in fact it had the opposite effect on me.
Unless you are receiving advice from a doctor for ways to increase your appetite, you might get advice on the internet that is detrimental to your health, and well being.
For me Marijuana increases my appetite, and I use it for medicinal purposes. The increased appetite is a side effect of the medicine, but it's a definite side effect that many people will concur to. I'm not saying you should smoke pot though. I am not recommending you take any drugs without doctors orders.
My best advice is don't use heroin. It's a dangerous street drug. Consult with a doctor for the best advice regarding your appetite.
I hope my answer helps.
Yeah but I’d try cannabis first. The munchies is famously linked to the plant. Better doing that than March to the brink of death to help you eat a Sunday roast