Suggestions for curbing hunger/excess eating?

I am injured and won't be able to exercise for 3 weeks...Do you have any tips for what to do so I don't gain weight? I know that drinking diet pop tends to curb my hunger, as does chewing gum. Also, a person can only eat so many carrot/celery sticks. I will eat decent foods (with protein and fat) but am used to munching all day (I generally run 5-6 miles and end up walking another 3-4 throughout the day so this is a HUGE shock to my system) I am really concerned about gaining weight...thanks for your help!