We're hardwired to obsess about food. Our ancestors' primary focus was their next meal, and evolution ensured that the focus stayed with us. Scarcity has plagued us until relatively recently: Our parents and grandparents experienced it during world wars and the Great Depression, and it's the reason they demanded we clean our plates. This helps explain why we feel guilty leaving food.
Then there is the very strong influence of our culture. Food plays a major role in every big event—birthdays, holidays, weddings, even funerals. Think of the way we denote financial success: "Make dough." "Bring home the bacon." "Be the breadwinner."
So thinking about food is only natural, and believe me, you're not alone. When you start obsessing, have a bite—just make it a smart one. I don't leave home without an insulated snack pack filled with nutritious items. To avoid being at the mercy of vending machines and fast food restaurants, fill a pack with fresh fruit, veggies, nonfat yogurt and whole grain cereals, and nibble when so inclined. Then reduce the size of your meals to make room for the calories you get from snacking. Confronting your obsession with food that's chosen wisely really works.