8-5 is the a great shift to stay healthy IMO. If you are a morning person you can wake up and do some cardio, cook your own breakfast and pack a lunch before going to work.
Its cool to keep snacks at your desk just make sure they are healthy, I keep peanut butter, almonds, and bananas at my desk, and additional fruit, chicken salad, and water in the fridge for snacks.
Getting off at 5 gives you time to go to the gym after work and come home and eat dinner and prepare meals for the week etc...
You can't stay healthy on a 8am-5pm shift then its you doing it terribly wrong.