its a huge speculation and ridiculous. How do they figure? What skinny people consume less air than fat? Aircraft doing food drops from international aid efforts in famines pollute less than the people would if they were well fed? Wheres the math on this?
I've often wondered how US Govt rationalized the corn to ethanol thing.
This study purports to explore that.
Yes it is ridiculous, that was the point; but that doesn't mean it's not true.
It's pretty obvious that a body that metabolizes less carbs will emit less CO2, and even more obvious that starving people have less offspring and die sooner.
The study is not available to me from here, but since it's Princeton, it is likely to be credible.
Here is the link, if you have access:
http://www.sciencemag.org/content/347/6229/1420.short