Carbohydrates of any kind allow our body to produce chemicals (I think it is serotonin in this case but am not 100% sure) and it often helps us to sleep.
I find similar responses to food later in the day.
Good luck with your behavior around food tomorrow. Regardless of your consumption know that for me food behavior was not a personality problem but a journey around which I could heal.
I am a natural morning person so know that this next part may not apply. I have to be careful to not exercise to late in the day.....or the feel good endorphins keep me up. I have to be sensitive with other things later in the day also for similar reasons. If only my life could be lived all before 10am I would be a much happier person.
For me later in the day eating is in part because of fatigue though also, as it often is later in the week too.