Which term is used to describe the process of the conversion of food to energy to run cellular processes?

There is a condition known as Gastroparesis, which simply is a VERY, VERY slow metabolism. Most regular people, (no pun intended), digest their food from stomach to small intestine in roughly 2-4 hours, however, we know of a person that takes about 8-9 hours from stomach to small intestine. She has many medical issues & is a medical enigma, literally! No one has been able to figure her out, how to help her, meanwhile she struggles day by day.

i got fast metabolism