I had a feeling once about mathematics — that I saw it all. Depth beyond depth was revealed to me — the Byss and the Abyss. I saw — as one might see the transit of Venus or even the Lord Mayor’s Show — a quantity passing through infinity and changing its sign from plus to minus. I saw exactly why it happened and why tergiversation was inevitable — but it was after dinner and I let it go.
    –Winston Churchill

 

It seems that Ghrelin, a hormone that is key in causing hunger, also improves memory. Ghrelin goes up when the stomach is empty and goes down when the stomach is full.

This suggests one reason that its harder to remember things one learned after lunch( or dinner.).