You don't have to dip the sushi in soy sauce, BK. In some circles, it is actually insulting to do so - the sushi chef has already seasoned the morsel properly, and it needs nothing more to add to the flavor. Of course, this depends on the skill of the chef, and the quality of his ingredients, which reflect upon his skill.
Fortunately, there are all sorts of other options in Japanese cuisine. And I mention it as another option for you to try, in your pursuit of a delicious, healthy, and low calorie diet.