I think intense exercise is necessary.

Doing intense workouts definitely makes a difference in my body's energy levels.
I believe one of the many reasons modern people suffer from boredom and depression stems from a lack of primal movement.
I'm talking about more intense movements rather than just static walking or slow jogging.
Or perhaps intense sports where you have to read, predict, and respond to an opponent's movements would facilitate brain activity and stimulate the secretion of necessary hormones and dopamine.