Hi. I have that problem, too. I would never have anything sugary/starchy with a meal unless I was planning on trying to fall asleep within an hour. I actually use this to my advantage when I'm working an odd shift and I otherwise might not be tired early enough. Your meal wasn't terribly high carb, but that would definitely put me to sleep.

I even get sleepy if I eat too large of a LC meal. It's not fun at work. I've had to cut my lunch breaks short and get back to work early because I start nodding off at the table. There's not much I can do but keep the meals modest, even if I think I could eat a horse.

One theory I heard is that with any substantial food intake, your body has to rather suddenly increase circulation to your stomach and intestines. With less blood flow to the brain, you get sleepy.