Im not really sure. I dont like doing sexaul stuff after eating and i get grumpy when hungry =p
I once had a lovely Italian dinner with an ex boyfriend. After finishing the meal, we proceeded to light every candle in the house and got romantic on the living room floor. Foreplay was moving along at a comfortable pace when I decided to kick it up a notch. I started licking his body, working my way ever closer to the ultimate prize. When I swallowed his cock, my stomach revolted and emptied - all over his crotch.
I have never given head with food in my belly ever since!
Now that I think about it, I prefer a light meal, (although we have sex often enough that we do it without regard to this.) I realize I get a little heartburn when I swallow on an empty stomach. So, probably ideally, a light meal or snack is good.
A few years ago, we went to Sal and Cavaro's (it's a Brazilian Meat Orgy, I think it has gone out of business.) It's an all you can eat place, a salad bar, a side dish (I think that's what it was) bar, and then the bring you meat on swords, and just keep doing it.
We went, and My Man kept saying (because he'd been there before, bringing clients out to wine and dine the pants off of them) "Pace your self." I'm thinking, "I KNOW how to eat." I didn't realize how much I ate until later (I rarely overeat, I usually leave myself a little bit hungry, as I think it's more healthy) Well, this night, I had to unzip my skirt in the car, I got home, kissed the kids, took a gas pill, and just got into bed (it was early) and just lie there moaning. Rare for me, I told My Man, (I actually whined) "Don't touch me!" (Yes, he bought me dinner, he almost always gets laid. Not this time, buddy.) I lie there until morning, falling asleep and not moving until hours later.
There is no way I could have given a BJ in that condition. But, I have probably eaten that much about 3 times in my life.
I've only given oral sex to women, and I don't really think what I've eaten really affects the activity, unless it's something that makes me burp (burping into a girl's vagina just sounds disrespectful), is really smelly (e.g. garlic), or I'm so full that I just want to sleep.
When it comes to anything sexual I'd rather do it on an empty stomach. When you've just eaten there's a much greater chance that something is going to come back up on you in some way (even just as a burp) and it's also so much more uncomfortable.
I've never thought about it, honestly. I don't like to be uncomfortably too full, but I don't like my stomach to be growling either. I guess a light meal or a snack would be good, as someone upthread posted.