An obese person could not get elected today, but if standards of personal beauty change so that we revert to the historical norms wherein it was better to be obese than starvishly thin, then yes. We live in a land of plenty where obesity is associated with being poor, not wealthy enough to afford excess food. Once the world population reach 20 or 30 billion, I imagine being overweight will once again be considered better than being underweight.
It won't: birthrates across the world have been in a downward trajectory since the early 90s: the population will probably peak at around 10 billion at the end of this century and afterwards will slowly drop.
Because we all know that trends continue forever, right?
China is seeing the beginning of the end of the one child policy taking place now. I would not at all be surprised to see China in reaction to that policy once it is finally gone, see a baby boom take place with two child families seen as the minimum desired size by mid-century, rather than a maximum desired size as it is now. China has set itself up for seeing the ability to provide for multiple children as the ultimate status symbol to say that you've arrived. That's also true to a lesser extent in India. That isn't to say I see the world population reaching the 20 billion mark by 2100. I do see the world population continuing to expand until food prices increase markedly from their current historically abnormal low value as measured by the percentage of per capita income devoted to them.
The main reason China hasn't repealed the One Child Policy is because the Chinese government is afraid that if they do so, the fertility rate will automatically spring back to five children per woman. This won't happen: no country with China's current HDI level has anywhere close to that fertility rate. In the very largest cities, such as Beijing and Shanghai, the fertility rate is actually at or even below 1, indicating that some women aren't even having their one allotted child. Also, there are various ways by which families can get around the one child policy, and the policy isn't enforced as rigorously in the countryside, where most of the population still lives.
It's also significant to note that Taiwan and Hong Kong both have lower fertility rates than Mainland China has as an aggregate, despite the absence of the one child policy in both.
Family sizes in India have always been large, and have begun to decline slowly but significantly recently; the same is true in Bangladesh and even Pakistan, after a half century or so of explosive population growth.
