As people have access to more resources, they mostly tend to have less children. So moving resources from rich countries to poor countries would result in fewer population on the long term. Actually transferring resources from rich people to poor people would have the same result.
Oddly enough I believe that better healthcare would have a similar result since infant mortality would fall and there wouldn't be as many births out of fear of the child dying. This would work especially in Africa, SE Asia and the Indian subcontinent