you may want to first check with your state’s laws about the scope of titles such as ‘nutritionist’ or ‘dietitian’ but it is my understanding that you cannot do that unless you are an RD.
However, that does not mean that you cannot talk about nutrition and give your clients sound advice. The latest issue with IDEA Fitness Journal has an entire addition on food which talks exactly on the issue of scope of practice for personal trainers.
I know that it can be quite tempting to want to give meal plans to clients but stepping into the minefield of nutrition in the presence of prescription drugs is almost dangerous in my opinion. Speaking for myself, I feel that I am becoming increasingly reluctant to address it the more I know about interactions and interrelations. The moment you put pen to paper and add your name to it, you create a responsibility (and liability) for yourself.