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