Eating Burns Calories Too
This process is called thermogenesis (meaning heat generation) and it is designed to regulate body temperature -- to keep the body warm.
Some tips:
Eat early and often. Metabolism naturally slows down during the latter part of the day, so burning off a big breakfast is easier than a big dinner. And if you must eat later, stick to protein and veggies. Pure protein has the most thermogenic effect of all foods (30 percent of its calories are used during digestion). Try eating several minimeals throughout the day to keep your furnace stoked.
Eat complex carbohydrates and protein. Your body has to work much harder to break down fiber and complex carbs (whole grain foods) than it does with simple sugars and carbs.
See I always knew I loved to eat for a reason :)