system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why do people have such a strong urge to take a nap when you have a full stomach?

Couldn't find a decent answer on here or Google.
gpt
Basically, your nervous system has two 'modes' - Sympathetic, which gives a 'fight or flight' response, and Parasympathetic, which tells your body to 'rest and digest'.
When you eat a ton of food, it triggers your parasympathetic nervous system, so your body focuses more on digesting your food than activity.
Eating a lot of food also causes your pancreas to make insulin, which in turn causes your brain to produce certain neurotransmitters (serotonin and melatonin to be precise) which make you drowsy.