Answer: holla! The question you provided is not complete, but, let me explain one or two things in order to be able to solve this kind of question.
Step-by-step explanation:
''...To persuade my fellow students of the benefits of a healthy diet and aerobic exercise the phrase the benefits of a healthy diet and aerobic exercise...''.
The statement above is what is called the specific purpose statement. Specific purpose statement can be declarative, informative or it can be persuasive.
A specific purpose statement is based on a central idea. For instance in the above statement in the question the Central idea there is;
==> Educating students/young people on Balanced diet and its importance. Also, the health benefits of physical fitness or exercise.
One of the things to research In order to give a great specific purpose statement is your audience. You must know your audience, for instance, the audience in the question are students/young people.