Refined foods are foods altered from their original state. In exchange for altering the texture of the original grain or sugar, nutrients are lost and shelf-life is generally increased.
A good rule of thumb when trying to contrast whole versus refined foods is that whole foods do not have a long shelf-life. Boxed and packaged foods generally contain refined grains and sugars. Additionally, foods made with white sugar and flour that have been refined are no longer whole foods. The human body does not process refined foods in the same way as whole foods, partially due to the decreased fiber content in refined foods. Refined foods are also generally higher in calories than whole foods.