In her speech, Laura plans to use the problem-solution organizational pattern to describe the problem of obesity and her solution, which is for Americans to eat lower-fat diets. When should Laura describe and define obesity?

First.

Explanation:

According to the Organizational pattern of Public Speaking, five patterns can be used for writing a public speech.

The problem-solution pattern is one of the five organizational patterns of public speaking. The format of this pattern is that it begins with the introduction of the problem and then states the solution. The purpose of such speech is to persuade the audience to form a perspective regarding the problem.

In the given case, Laura, according to the format of the problem-solution pattern, should begin with stating the problem. She should describe and define obesity at first in her speech then state the solution.

So, the correct answer is first.