I think that the best thing that you could do is to ask to speak with your boss in private when he (or she) has time, and be honest. If you make up some BS reason, chances are, they will smell it.
The fact that you want to travel while you are still young enough to enjoy it is not something that would be seen as dissatisfaction with your job. This is a decision that is all about you and nothing to do with the job.
As a travel writer, I know (been traveling for 6 years), the rest of your life will forever be changed because of a little one year trip. And the value of that change is something that NO JOB could ever equal. Jobs will come and go, money will be made or lost . . . but the life experience that you will gain on the road is something that no one will ever be able to take away from you ; you will never loose it ; it will become a part of the new you.
Just do it!