How do I put these ideas into a thesis statement? Even though not everyone eats at a fast food restaurant, we are still in danger of risking our...

Sometimes you can take a question and turn it into a statement/argument and use it for a thesis statement to begin the writing process.

For example, the question, "Do we all suddenly abandon our local supermarkets and head to the farmers market?" can be restated as: To insure healthy bodies we should eat locally by shopping at the local farmers' market where organically grown local produce is available. To support this idea you could list all the reasons why (giving each a paragraph of their own) and the positive results from making the change to eat locally. Google "Slow Food Movement" you may find some interesting ideas.

For a really great article on how to write a thesis statement look at Perdue University's online writing lab (OWL).