Reactive foods are foods that are prone to allergic reactions. Even if you aren't allergic to foods you can still have very high sensativities to them. Over time, eating foods that you are sensative to or allergic to can cause your body to store fat and cause other things such as anxiety and weight gain. If you think you may have some food allergies or food sensativites then I would suggest reading the book "The False Fat Diet" to everyone!
This book is full of great information and it opened my eyes to what allergies can really do to a person't body. I also lost 7 pounds in 1 week doing their elimination diet!
Adria