If you have just eaten, your body will secrete insulin. Insulin is the hormone that allows glucose to enter cells. That way they will have the proper energy for their normal functions.
If you have not eaten for a while, your body is running out of glucose to feed the cells so it needs to secrete another hormone called glucagon. This hormone is the complete opposite of insulin because it breaks down glycogen, proteins and fats into glucose.
I'm thinking it might be fossil evidence. Hope it helps!
