Until recently I was using Musashi Bulk protein powder. Since running out I already feel lethargic, though I suspect that might be at least partly due to continuing high levels of exercise without as much energy, not just protein.

I'm now considering getting Gold Standard 100% Whey (and 100% Casein as well, but that's way more expensive over here in Australia). That'd last quite a while but what happens if I stop taking it? Will muscle gain and body fat reductions be reversed? Will it affect my energy levels if I increase calories from other sources?

Thanks.