Consider the possibility you were somehow able to feed all of the people in the places in the world where life expectancy is low due to malnutrition, malnourishment, starvation, and/or contamination (eg. with low-cost GMO crops). You now have a rapid surge in the population because of the people who would normally die are still alive and live in places where there there is very likely already severe overcrowding, disease, poverty, and unrest who will only add to the problem. Don't feed the poor.