If you need to be taught how to plan a balanced diet, you will be taught. If you ask for help, it is there for you. There is a lot of information out there and more often than not, people generally know that a diet of junk food isn't healthy. Just as a diet of all fruit each day isn't healthy. (I know that you were just making a point) You will also be taught self-reliance. It is entirely up to you if you want to succeed. WW gives you the tools to succeed, but if you don't initiate your education yourself, no matter what tools you are given, you won't succeed.
The United States Department of Agriculture has an excellent web site
http://www.mypyramid.gov/ that teaches how to create balanced diets.
I had a basic knowledge of what to do, and I was given some sample daily meal plans. It was up to me to continue on with those suggestions and pick foods that would follow the healthy guidelines.