YOU ARE WHAT YOU EAT and if you are eating pest resistant GMO corn which kills insects with poison then your body and gut bacteria will adjust and start manufacturing the pest killing toxin also causing irreversible harm to your health. There is now scientific evidence that this is true and this is all the more reason why GMOs should be labeled and many of them tested for long duration effects on humans, especially the ones resistant to pests and herbicides.
80% of processed foods contain GMOs in the United States so you should become concerned if you are not yet. Not all the processed food has GMO plant DNA in it so there is no need to panic with fear but research foods which do contain GMO plant DNA and eat them with caution and in moderation because it will affect your body metabolism and that of your offspring sooner or later.
Here is a link to the proof which you should try to understand for your own future health and well being.