We found more sites for research of why pizza is unhealthy.

1. http://www.bottomlinepublications.com/content/article/diet-a-exercise/pizza-a-healthy-or-unhealthy-fast-food-choice

2. https://answers.yahoo.com/question/index?qid=20070606121120AA93T46

3. http://www.bbc.com/news/health-26255931

4. http://straighthealth.com/pages/qna/pizza_healthy.html

5. http://slice.seriouseats.com/archives/2013/02/poll-is-pizza-unhealthy-way-or-no-way.html