A small snack to keep my metabolism going?!

These days, I don't really feel like eating, and I'm supposed to have a tuna salad for lunch, but just the thought of me eating that, makes me feel disgusted. I was wondering, what can I eat instead of a tuna salad that will also keep my metabolism going?

Any ideas? Maybe something low in carbohydrates :) ..

I am looking to lose a pound or two, so not something fattening. I am 15 years old, 5'3 and 113-114 pounds.