Not to be difficult...(although I often am)...
Appetite suppressents are like stimulents in that, by the time they work, you start to build up a tolerance to them and they eventually backfire.
Believe it or not, the best appetite suppressent advice probably came from your mother when she told you as a kid; "Don't eat that piece of candy, it'll spoil your appetite! She was right. Sugar supresses the appitite. So if you eat a piece of fruit 20 minutes before a meal, you'll probably get full faster.
Beyond that, I have to give the one answer that is tried and true yet people don't like to hear it. But it works every time.
Will power.
You need to have control over your mind to succeed in anything. It must become a lifestyle. When you accomplish that, it puts you one step closer toward accomplishing the next, more difficult task. And so on.
Or, you can just ask someone else what drugs to take.