The Neurobiology of the Obesity Epidemic

I recently read an interesting review paper by Dr. Edmund T. Rolls titled "Taste, olfactory and food texture reward processing in the brain and the control of appetite" that I'll discuss in this post (1). Dr. Rolls is a prolific neuroscience researcher at Oxford who focuses on "the brain mechanisms of perception, memory, emotion and feeding, and thus of perceptual, memory, emotional and appetite disorders." His website is here.

The first half of the paper is technical and discusses some of Dr. Rolls' findings on how specific brain areas process sensory and reward information, and how individual neurons can integrate multiple sensory signals during this process. I recommend reading it if you have the background and interest, but I'm not going to cover it here. The second half of the paper is an attempt to explain the obesity epidemic based on what he knows about the brain and other aspects of human biology.

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Are Animal Crackers Paleo?

Every child loves animal crackers, those sweet and crunchy animal-shaped biscuits. But are they compatible with a Paleo diet? Some people might think they already know the answer, but consider this: our ancestors evolved on the African savanna, eating the plants and animals found there. Inside each box of animal crackers is an assortment of tiny savanna creatures such as giraffes and elephants.

To get to the bottom of this, I interviewed Robert Pearson, CEO of Animal Cracker Products Inc., who explained to me how these crackers are made.

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Ancestral Health Symposium 2012

I recently returned from AHS12 and a little side trip to visit family. The conference was hosted at Harvard University through the Harvard Food Law Society. Many thanks to all the organizers who made it happen. By and large, it went smoothly.

The science as expected ranged from outstanding to mediocre, but I was really encouraged by the presence and enthusiastic participation of a number of quality researchers and clinicians. The basic concept of ancestral health is something almost anyone can get behind: many of our modern health problems are due to a mismatch between the modern environment and what our bodies "expect". The basic idea is really just common sense, but of course the devil is in the details when you start trying to figure out what exactly our bodies expect, and how best to give it to them. I think our perspective as a community is moving in the right direction.

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Beyond Ötzi: European Evolutionary History and its Relevance to Diet. Part III

In previous posts, I reviewed some of the evidence suggesting that human evolution has accelerated rapidly since the development of agriculture (and to some degree, before it). Europeans (and other lineages with a long history of agriculture) carry known genetic adaptations to the Neolithic diet, and there are probably many adaptations that have not yet been identified. In my final post in this series, I'll argue that although we've adapted, the adaptation is probably not complete, and we're left in a sort of genetic limbo between the Paleolithic and Neolithic state.

Recent Genetic Adaptations are Often Crude

It may at first seem strange, but many genes responsible for common genetic disorders show evidence of positive selection. In other words, the genes that cause these disorders were favored by evolution at some point because they presumably provided a survival advantage. For example, the sickle cell anemia gene protects against malaria, but if you inherit two copies of it, you end up with a serious and life-threatening disorder (1). The cystic fibrosis gene may have been selected to protect against one or more infectious diseases, but again if you get two copies of it, quality of life and lifespan are greatly curtailed (2, 3). Familial Mediterranean fever is a very common disorder in Mediterranean populations, involving painful inflammatory attacks of the digestive tract, and sometimes a deadly condition called amyloidosis. It shows evidence of positive selection and probably protected against intestinal disease due to the heightened inflammatory state it confers to the digestive tract (4, 5). Celiac disease, a severe autoimmune reaction to gluten found in some grains, may be a by-product of selection for protection against bacterial infection (6). Phenylketonuria also shows evidence of positive selection (7), and the list goes on. It's clear that a lot of our recent evolution was in response to new disease pressures, likely from increased population density, sendentism, and contact with domestic animals.

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Beyond Ötzi: European Evolutionary History and its Relevance to Diet. Part II

In previous posts, I described how Otzi was (at least in large part) a genetic descendant of Middle Eastern agriculturalists, rather than being purely descended from local hunter-gatherers who adopted agriculture in situ. I also reviewed evidence showing that modern Europeans are a genetic mixture of local European hunter-gatherers, incoming agricultural populations from the Middle East, neanderthals, and perhaps other groups. In this post, I'll describe the evidence for rapid human evolution since the end of the Paleolithic period, and research indicating that some of these changes are adaptations to the Neolithic (agricultural/horticultural/pastoral) diet.

Humans have Evolved Significantly Since the End of the Paleolithic

Evolution by natural selection leaves a distinct signature in the genome, and geneticists can detect this signature tens of thousands of years after the fact by comparing many genomes to one another. A landmark paper published in 2007 by Dr. John Hawks and colleagues showed that humans have been undergoing "extraordinarily rapid recent genetic evolution" over the last 40,000 years (1). Furthermore:
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Beyond Ötzi: European Evolutionary History and its Relevance to Diet. Part I

In the previous post, I explained that Otzi descended in large part from early adopters of agriculture in the Middle East or nearby. What I'll explain in further posts is that Otzi was not a genetic anomaly: he was part of a wave of agricultural migrants that washed over Europe thousands of years ago, spreading their genes throughout. Not only that, Otzi represents a halfway point in the evolutionary process that transformed Paleolithic humans into modern humans.

Did Agriculture in Europe Spread by Cultural Transmission or by Population Replacement?

There's a long-standing debate in the anthropology community over how agriculture spread throughout Europe. One camp proposes that agriculture spread by a cultural route, and that European hunter-gatherers simply settled down and began planting grains. The other camp suggests that European hunter-gatherers were replaced (totally or partially) by waves of agriculturalist immigrants from the Middle East that were culturally and genetically better adapted to the agricultural diet and lifestyle. These are two extreme positions, and I think almost everyone would agree at this point that the truth lies somewhere in between: modern Europeans are a mix of genetic lineages, some of which originate from the earliest Middle Eastern agriculturalists who expanded into Europe, and some of which originate from indigenous hunter-gatherer groups including a small contribution from neanderthals. We know that modern-day Europeans are not simply Paleolithic mammoth eaters who reluctantly settled down and began farming.

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Lessons From Ötzi, the Tyrolean Ice Man. Part III

There are two reasons why I chose this time to write about Otzi. The first is that I've been looking for a good excuse to revisit human evolutionary history, particularly that of Europeans, and what it does and doesn't tell us about the "optimal" human diet. The second is that Otzi's full genome was sequenced and described in a recent issue of Nature Communications (1). A "genome" is the full complement of genes an organism carries. So what that means is that researchers have sequenced almost all of his genes.

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