I had to do an essay on why it is important to eat breakfast in high school a couple years ago. It was a horrible essay and presentation but I still got 100% because the teacher loved me.
But then again that was cooking class and this is some science class. A little more in depth than "You feel bad if you don't eat breakfast" is expected I suppose.
Something on scurvy and how it affects the body and how vitamin c prevents it?
How about how maggots form out of rotten food seemingly by magic?
The effects of carotin on colour of skin?
I'm not sure exactly what you're looking for. What grade is this for? What is the class?