Dear Protestant Boyfriend,
Just a note about fasting for Orthodox Christians. The Orthodox fast because:
1. Christ expected it to be normative in Christian life. (Matthew 6:16, "When you fast...")
2. It strengthens a Christian's self-will to look beyond what he/she wants and see what is good for others, for what God wants. It acts as the ultimate anti "my god is my stomach," literally.
3. In order to have money to give to the poor as we save on food costs.
4. We fast so that we CAN feast... If a person never goes without something, you can't add that thing back in with joy when it is time to celebrate! :-)
I've heard it said (though not from a priest) that Orthodox married couples are expected to abstain from sex during fasting periods. (I Corinthians 7:5) I think a case could be made for sex on Sundays during fasting periods, but I'm not sure. Also, married couples are NOT expected to abstain from sex during their first year of marriage. It is thought that the first year of marriage is so hard that couples very much need sex to strengthen their bonds and give joy.
There are actually four fasting periods a year (they vary in seriousness and length). Not everyone fasts at these other times, but most Orthodox take a stab at fasting during Great Lent.
Please expect me to be bad at fasting. This happens. Part of abstaining from things for this length of time is seeing your own frailty and dependence upon God. Also, more important than the fasting itself is prayer, both individual and corporately in the services of the Church.