You must mean the Advent or Philip's Fast, depending on which part of the Great Schism you fall. Excellent. Catholicism/Orthodoxy is a widely respected religion that is only basically known to non members. You can tell your coaches that as a practicing Catholic/Orthodox Christian, you are fasting to be closer to your Lord and that as part of your fast, you must abstain from all types of physical arousal, whether sexual, digestive, or overexertive and you pretty much have carte blanche to fast away as you wish and are legally protected.
Unless, I've totally missed something and it isn't a Christian fast, but I believe Ramadam this year is going right now, so that rules out Islam and as far as I know, the other major religions don't have a four week(or forty day) long fast right before Christmas. Sorry if I'm off though. Happy Fasting.
Oh and Boris the Pillager is an old boxing nickname. My name is Yevgeniy, but call me James.