Input and output would have to be considered as well as length for life when comparing with previous generations.

Most of us city dwellers sit on our way to work, sit at work, walk to a coffee or a cigarette, sit for more work, sit on our commute home, sit for dinner, sit and watch tv. Then find it difficult to find time to do a half hour of exercise.

Yet we are living close to twice as long as our Roman counterparts. A lot of whom died to minor diseases by modern measures. The diseases we are dying of look like those that take longer than the ancients lived and a lo of these diseases such as gout were limited to the nobility.

We have old rich lazy people diseases that manifest themselves well beyond the average lifespan of most humans who existed before us.

As for evolution and it's speed just look at how quickly being lactose tolerant spread through populations who drink milk. Similarly look at the lack of tolerance to alcohol for populations that had not been exposed to alcohol. A small advantage constantly applied will spread relatively quickly.

Given just these two examples is it not possible that most of us have a higher tolerance for grains than our nomadic ancestors. After all jus look at the high rates of type 2 diabetes in Australa's aborigines. Sure their diet is pretty bad, but they suffer far worse than their western counter parts on similar modern diets of alcohol and junk food.