Why do you feel tired after a big meal?

Why do you feel tired after a big meal?

There is a cycle there where the siesta time in the afternoon is part of the twenty four hours cycle. So peak sleepiness is around four in the morning, but there's a second peak of sleepiness that occurs between twelve and three in the afternoon. One element of the lunchtime meal causing sleepiness is that, if one was thinking about something like a Christmas meal, then usually the alcohol and everything else thrown in is having impact. Some people would say that it's the reason that siesta has evolved at all and one of the reasons sleep might have to evolved.