Fill Up on Fiber

Fiber takes up space in your belly without adding many calories, says Rolls. It also slows the rate at which food travels through your digestive system, she says, and that keeps you feeling full longer.

Fruits, vegetables, and whole grains all pack lots of fiber and a hefty dose of vitamins. Start your day with a bowl of oatmeal or whole grain cereal topped with fruit, add milk or yogurt, and chances are you'll make it to lunch without a trip to the vending machine.