An apple a day may keep the extra weight away. Penn State researchers discovered that people who ate a large apple 15 minutes before lunch took in 187 fewer calories during lunch than those who didn't snack beforehand. What's more, they reported feeling fullcr afterward, too. Sure, the fruit is loaded with belly filling fiber, but there is another reason apples help you feel full: They require lots of chewing, which can make you think you're eating more than you really are.*