I notice a moderate decrease in appetite and some amount of mood/energy level change. Nothing too drastic though, but I guess I'm comparing it to more powerful pills I have tried. What I do notice the most is that when taken 30 minutes prior to my workouts, for some reason I can work out longer and harder than normal--I don't get exhausted as quickly. The pills are kind of big and red and taste like a piece of hot chili pepper. I only take this once a day, as the one time I took it twice I felt sick. I do find it difficult to fall asleep on days I have taken this. No jitters though.