For your case, you just need to eat a lot. Make sure your calorie intake exceeds your daily calories burned. The fact that you lose weight fast has nothing to do with what supplements you're taking; One you stop your workout or whatever, your body will go back to its natural state. If you're usually skinny, then you'll be skinny. Same thing goes for fat people. If they stop working out, then they'll simply just regain that weight they lose. Everyone's body is "programmed" differently.
So, for you to be 160 pounds is 'unnatural' for you specifically, so to maintain it you must continue your high-calorie diet and your daily workout, or else very shortly you'll lose it all.
As for which supplements to take, that would depend on your diet. Just make sure you have high protein, high carb diet; and if that includes meat, then you're good to go.