Bueno provecho means bon appetit. (Funny how I translate something to English and it ends up in French.)
But the phrase buen provecho cannot be explained so easily. But it’s much more than a phrase. It’s a cultural mindset. Saying buen provecho to someone when they are eating is the equivalent of saying bless you to someone who sneezes. I don’t know where I picked this up exactly, but I always always say bless you when people sneeze. This is actually not very common in Spain (the translation of bless you would be either salud or Jesús in case you were wondering). But it doesn’t matter much because no one really says it.
What people DO say is buen provecho. They say it to friends, coworkers, even strangers–anyone who is immersed in the sensual experience of stuffing wonderfully, probably, oily food into her/his mouth. Food is such a central part of Spanish culture. It’s not just nutrition. It’s not just one more thing you need to do today. It’s social and it’s sensory. It’s one of the many things that make life so enjoyable and it should always be appreciated, no matter what you’re eating.
Case in point: last weekend I was waiting in a train station in a town outside of Madrid and a bunch of Spanish tweens were sitting on the floor of the station consuming a huge bag of cheese puffs (or something of the like). An older man walked by the kids: bueno provecho he said.
That’s right kids, enjoy that salty, crunchy trans-fat. Life is too short to do otherwise.