I am a bit of a fan of Charles Darwin. I think the Right gives him waaaaaaaaay too much flak for simply observing the way species evolve over time, and then proposing a theory about how it might work. The theory makes sense, and what's more, it's supported by study after study.
Believing those things and telling you that does not make me or Darwin an atheist. (I would argue that it adds enlightenment to my worldview actually, but I digress).
The New York Times has published an interesting article positing the idea that humankind (Homo sapiens) may possibly over time be able to evolve a greater ability to metabolize high carb foods. You can read the article here.
I have two problems with this idea (in other words - I disagree).
First, and probably most important, is that humans are no longer evolving in a closed system. No other species on earth has the ability to think. Therefore, no other species has doctors, pharmacists, therapists, or researchers to develop treatments aimed at compensating for evolutionary shortfalls. Humans do. In short, we now prolong lives that "survival of the fittest" would have weeded out. I am not belittling the health care field. I am just pointing out that evolution can no longer work unfettered on humans (and many other species, thanks to human intervention).
Second, The consequences of poor dietary habits (heart disease, diabetes, and obesity among others) are cumulative over long periods of time, and do indeed shorten life, but they do not (I argue) lessen reproductive capacity. Men and women die of heart attacks, cancer, diabetes, etc., after they have had (and mostly raised) their babies, more often than not. So, the mechanism by which natural selection works is short circuited. As the academics might say the evolutionary pressure is weak.
If you had a heart attack immediately upon eating a double-cheese-bacon burger, the theory proposed in the article might have legs, but for now, not so much.