For years I was looking for the appetite holy grail, only to find there isn't one, well not a pill or anything like that.
Hopefully my findings will save you a lot of time.
Ok, if you are training well, your appetite will improve a bit, probably not enough for mega growth though. And I mean not overtraing as well as not exercising enough.
Do you stress a bit, does this knock your appetite? Get into yoga, chi gong tai chi type stuff.
I can't eat a solid breakfast. You must take liquid food, some sort of shake with protein.
My daily shake for three meals is/was 500ml milk, 80g protein powder, 100g oats, 2 tablespoons olive oil.
Now the big trick is to build up calories slowly over a month or so spread over 6 meals. 3 solid 3 the shake. This takes a thing called discipline, and that's the real problem with most people.
If you feel sick, suck on some ginger. Then carry on eating.
I took my calorie intake from 1800 to 2200 reached a platue, then started adding in the shakes to reach 3200 within a month.
The gains came, they never did before, eating is the key.