Maybe get a good test done beforehand to have something to compare to a few months down the line?
For me it was an easy decision. I looked at the foods that I was eating and the ones I wasn't. Before this I rarely included veg in my diet - now I have loads of it each day. That's got to be a good thing, no? Also, I'm more aware (well, trying to be) of what's in the food I'm eating, I'm learning quite a lot about nutrition.