What is the Spartan rule for eating?

Could you elaborate on the "Spartan rule for eating"? Is it a particular dietary regimen or a set of principles that Spartans adhered to in their meals? Were these rules centered around portion control, food types, or perhaps a specific time of day for eating? How did these rules contribute to the physical and mental strength of the Spartans? I'm curious to know more about the specifics behind this intriguing topic.