There are several devices that can accomplish this. But I'll focus on exaggeration/understatement for today. Exaggeration/understatement takes a concept and either overplays or underplays it for effect. The following is an example of exaggeration/understatement.
I've found this to be the easiest type of humor to use in illustrating serious subjects in a light manner. Simply take a fact from the article, and either exaggerate what is being said, or understate it in a way that drives the point home. Here is an illustration for a series I tied to the Atlanta Olympics. The concept of the series was "A Perfect 10 Olympic Trivia Facts." So each of the illustrations dealt with a sports fact related to the Olympics, exaggerated visually in each case. The item for this example was, "The first tandem rowing event in the Olympics was introduced by a team comprised of whalers."
illustrations copyright J.Pittman, 1994 and 1996
As an assignment, take a fact like, "No matter what your age, exercising can be beneficial." Think of an exaggerated or understated way of presenting the fact in a light and humorous way. It could be a workout gym scene in a retirement home, where a bunch of old codgers are preparing for a pole vault event with their canes, a lady with a walker is going at blurring speed on a treadmill, etc. The more elements like those that you add to the scene will heighten the absurdity of it all while still illustrating the fact of the benefits of exercise.