feed off
US /fiːd ɔːf/
UK /fiːd ɔːf/

1.
to eat something as food
:
•
The birds feed off the berries in the garden.
•
Many insects feed off decaying organic matter.
2.
to grow stronger or be encouraged by something
:
•
The comedian seemed to feed off the audience's energy.
•
Some people feed off drama and conflict.