Let's say I have a roughly humanoid race (similar size, form, activity level, etc.) that spontaneously generates any energy that they need via Magic. However, they still need to eat some materials in order to grow and repair their bodies.
Assuming that their biology is mostly the same to humans, other than the energy generation, how often and how much would they need to eat, and what would be good sources of food?
Their biology has not yet evolved the ability to create matter, and there is an upper limit to the amount of energy they can generate in a certain amount of time.