Given that “we need 2,500 kilocalories (kcal) each per day … the world’s total edible crop harvest could supply 4,600 kcal per person per day. However, of this 1,400 kcal is lost or wasted. A further 1,700 kcal is used as animal feed. But – crucially – the resultant meat and dairy products only provide 500 kcal for human consumption.” (http://www.eating-better.org/blog/3/Feeding-nine-billion-how-much-extra-food-do-we-need-to-produce.html)
If we put less of our global food crop into overeating, the bin and animal feed, we could feed the projected population of nine billion in 2050.
Also perhaps we don’t need two billion extra people.