Go figure - and Mom always said not to chew gum. The following is from a health web site:

Countering the Snack Attack
People who chew either sweetened or sugar-free gum after lunch feel full longer, have fewer hunger pangs, have fewer cravings for sweets, and eat fewer afternoon snacks -- compared with people who don't chew gum. (Check out this additional tasty way to eat less, not more.)

Tickled Taste Buds Signal "Full"
How does chomping gum suppress hunger? It's simple. When you eat, your taste buds are stimulated by the food. But the cool thing is that exposure to the tastes and smells of food also lessens how good it tastes. That, in turn, is one of the cues that signal your brain that you're full, so cravings go away. Chewing gum may have this same effect -- but without all the calories! (Discover why skipping meals increases cravings for the wrong foods.)