I got so tired of tuna and low fat mayo, I've tried it many other ways. Here is a good one, and healthy, too. This adds fiber and complex carbs. Net carbs added are very low:
Crumble tuna in bowl. Add chopped onion, chopped raw baby (or regular) spinach, chopped sun dried tomatoes (squeeze oil out first) and a couple tablespoons of a favorite salad dressing. (I tried it with low fat Italian, very good!) Toss everything together. Eat with a slice of whole wheat flatbread.
The sundreid tomatoes are high in fiber and licopene, which has been shown to reduce prostate cancer in men. I learned to like them for these reasons. Raw spinach is high in vitamins, minerals and fiber.