Hello there!
The energy from food molecules originally comes originally from the sun.
When you think about the process of which food is made, everything comes and lives on - plants. Plants take in energy from the sun, in a process called photosynthesis.
Then of course, we eat animals as well. Animals live on eachother as well as other animals. Therefore their energy comes originally from the sun.
I hope this helps you!
~Galexie