Physical Danger
Sometimes it's nice to kick your feet up and sit on your butt, but doing so for say, 10 to 18 hours at a time, tends to take it's toll on the body. Look, writers aren’t known for their amazing posture and six-pack abs. Sitting around hunched over, while packing on abs made of potato chips and candy bars doesn't necessarily do wonders for the physique.
Many writers gain weight while working on a show, mainly because the job is highly sedentary and food is everywhere. There's a fully stocked kitchen with everything from kombucha to ice cream sandwiches. You also have craft services, which is the food that's on set and is always delicious and is always bad for you. Beware—the life of a writer is filled with corn syrup, trans fats, and never-ending goodies. Great in theory, not necessarily in practice.