Obesity can be caused by a infectious disease is not the same thing as obesity, in general, being caused by an infectious disease. It would have to be caused by

Obesity can be caused by a infectious disease is not the same thing as obesity, in general, being caused by an infectious disease. It would have to be caused by a contagious, in general, to be able to describe the widespread prevalence of obesity as a pandemic, since the term pandemic is concerned with infectious diseases.