A prayer before dinner

[Objectivist]

I don't know how to handle this.  I have two religious friends, and whenever I go out to eat with either of them this is a problem.  I meet one only at restaurants.  He always says a prayer before eating.  It makes me feel awkward, as though by waiting until he's finished I am in agreement with the prayer.  I'm not.
I have another friend who I met for dinner at someone's house.  Before we ate she said a prayer, while we all waited.  (Several of us are non-believers).  
Again, the awkwardness while waiting for her to finish the prayer.  This is just me, but I find that to be a little rude and self-serving.
I am tempted to eat before she finishes the prayer, but that would be construed as rude.
I wish I knew how to deal with this problem.  Any suggestions?

I simply sit with my hands in my lap and wait.  It does not imply agreement.  I don't close my eyes but instead, look around to see who's eyes are closed and whose not.  It does not anger me or make me feel awkward.  I suppose it would be rude to take a bite and say "wow this is really good" during the prayer.  How would they know you were eating, their eyes are closed as they look inward to their imaginations, shutting out the real world.