As a former frequent business traveler, I can tell you it is amazing what even one timezone will do to you with regards to sleep. I reside in the CST, and traveling to the west coast would take me a few days to acclimate, and then I would fly back home to only fly to the east coast the next week.

Don't underestimate the impact of how a single hour of time can impact the brain. Two timezone differences to the human body can be huge.