The issue: I have trouble figuring out whether or not I would be better off feeding my sprite its favorite food, or a different material. Which would give it more heat?
The solution: It would be quite useful if there was a little shadow bar on the sprite heat meter that told you how much heat a material gives your sprite.
I think it's something like if the sprite is fed by its favoured material, its heat increases by double than what it would normally. This means that 5 star materials are obviously better than a favoured 1 star material.
Experiment, and upload to the wiki.