Obesitas: addendum

Ingediend door Ivan Janssens op ma, 12/07/2021 - 13:24

Ook dit artikel is een mooie aanvulling op mijn stuk over de obesitasepidemie. De auteur betoogt dat met de landbouwrevolutie we op korte tijd een heel ander soort dieet voorgeschoteld kregen: monotoon, arm in vitaminen en mineralen, maar rijk in calorieën. Hetzelfde, al vermeldt de auteur dat niet, kan in feite gezegd worden over de industriële revolutie. Die deed er dus nog een (heel) schepje bovenop vooral met industrieel geproduceerde poly-onverzadigde olieën. Het gevolg was dat we ons onbewust zijn gaan overstelpen met energie, veel meer energie dan ons lichaam gewoon was; terwijl ons lichaam onvoldoende tijd heeft gekregen om zich aan de gewijzigde situatie aan te passen.

How our diet outpaced our evolution, and how we can close the gap.

Omar Sharaki
Photo by Wolfgang Hasselmann on Unsplash

Caught up in the brief slice of time we occupy, it’s easy to forget how much the world has changed, and that many of the things we now take for granted were by no means commonplace, even just a few years ago. Perhaps, never was this quite so evident as it is today. We live in what historians have come to call the digital revolution. And although arguably the most groundbreaking, it is but the latest in a long chain of revolutions that have shaped the world we live in — and, in turn, us. But to best understand humans today, one must go back. Way back.

By most estimates, modern humans have been around for about 300 thousand years. There is little discord in the scientific community that over that time period, humans went through changes, both cognitive and physical. The Homo sapiens who painted on the walls of the Chauvet Cave over 30 thousand years ago will have exhibited significant genetic variation from their ancestors who set out of Africa thousands of years before. How similar these cave dwellers were to us, however, is where opinions differ.

Replica of a portion of The Panel of Lions in the Chauvet Cave in Ardèche, France — Wikimedia Commons

The period in human history inhabited by these artists, which started ca 70 thousand years ago, is referred to by Yuval Noah Harari in his book Sapiens, as the Cognitive Revolution. Around this time was when humans really started showing innovative displays in areas such as toolmaking, building and maintaining complex social structures, and even art. The conventional wisdom is that this period heralded the last significant changes to our biology, and that our evolution has since slowed to a crawl — if even that.

Among those who oppose this conventional wisdom are Gregory Cochran and Henry Harpending, authors of The 10,000 Year Explosion. In their book, they argue that as the world around us continued to change — and as we began bringing about change to the world around us — so too did our minds and bodies not only continue to evolve in response, but they did so at an unprecedented rate. Catalyst for this rapid change was one particular revolution that happened, as the book’s title alludes, around 10 thousand years ago: the Agricultural Revolution.

The Agricultural Revolution marked the shift from our previous hunter-gatherer lifestyle to a more settled existence. It’s widely accepted that this shift is what paved the way for human civilization; everything from writing to science to industry and eventually the digital era would not have been possible without our species’ widescale adoption of an agrarian lifestyle.

There are many reasons why agriculture was so crucial to our advancement, but what it essentially comes down to is food. To understand why this is, it helps to consider one of the key points Harari emphasizes in his book, and, in fact, the trait he most attributes our success to. That is, our unmatched ability for large-scale cooperation:

Ants and bees can also work together in huge numbers, but they do so in a very rigid manner and only with close relatives. Wolves and chimpanzees cooperate more flexibly than ants, but they can do so only with small numbers of other individuals that they know intimately. Sapiens can cooperate in extremely flexible ways with countless numbers of strangers. That’s why Sapiens rule the world, whereas ants eat our leftovers and chimps are locked up in zoos and research laboratories.

These large numbers required for effective, world-changing cooperation could simply not be sustained by a hunter-gatherer lifestyle. Farming, on the other hand, could produce 10 to 100 times more calories per acre than foraging, increasing the world population almost a hundredfold by the turn of the first millennium.

The essence of the Agricultural Revolution is the ability to keep more people alive under worse conditions

— Yuval Noah Harari, Sapiens

The human diet thus largely shifted from the varied assortment of wild fruits and vegetables, seeds, nuts, fungi, fish, and occasional game to a handful of domesticated plants and animals. Over the course of a few thousand years, more and more humans in different parts of the world started growing and relying on crops for their survival. This included wheat and barley, then peas and lentils in the Fertile Crescent, followed by rice and soy in China, and later maize (corn) and potatoes in the Americas and yams in Sub-Saharan Africa. These calorie-dense foods that could be produced at scale became the foundations upon which subsequent human development was built. Individual humans, however, did not necessarily become better developed for it.

Woodland strawberry (Fragaria vesca)Wikimedia Commons

With our new crop-based diet, often consisting mainly of a single food staple (e.g. potatoes), came a reduced intake of minerals and vitamins. Furthermore, the macro-nutrient that contributed the lion’s share of ingested calories, carbohydrates, interfered with the control of blood sugar and resulted in health problems such as diabetes — in particular, type 2 diabetes. So while a wheat field could support perhaps ten times more people than a foraging band subsisting on wild plants and animals in a comparably sized area, the foragers will have been relatively better-nourished and healthier than the farmers. As Harari puts it:

This is the essence of the Agricultural Revolution: the ability to keep more people alive under worse conditions

Cochran and Harpending make the case that different societies coped differently with these unbalanced diets, resulting in the descendants of those with earlier exposure to agriculture now being genetically somewhat better equipped to handle their adverse effects:

Populations that have never farmed or that haven’t farmed for long, such as the Australian Aborigines and many Amerindians, have characteristic health problems today when exposed to Western diets.

The authors attribute the higher incidence rates of type 2 diabetes in these groups and others with similar histories to a lesser degree of adaptation to high-carbohydrate diets. These adaptations also extend to alcohol tolerance as the brewing and consumption of alcohol were never far behind wherever agriculture took root. And while agricultural innovations did gradually improve the nutritional quality of food, they have also resulted in detrimental practices such as rice polishing and grain refining, and low-nutrient crops such as sugar cane.

Photo by Presetbase Lightroom Presets on Unsplash

It doesn’t take a dietician to know that pastries, fast food, and candy are bad for us, but it’s less obvious that many foods and dishes traditionally perceived as healthy have been thousands of years in the making, and regarded throughout as little more than energy sources. Today’s cuisines, as delicious as they may be, are simply the product of generation upon unquestioning generation eating and refining dishes built around a small subset of staple foods initially chosen, not because they were more nutritious, but merely because they were the most convenient means for our proliferation. To quote Harari:

If our minds are those of hunter-gatherers, our cuisine is that of ancient farmers.

This isn’t to say that a complete return to a pre-agricultural diet is required — or even possible for that matter. As noted by Harari, over 90% of the foods we eat today come from the handful of plants we domesticated between 9500 and 3500 BC — wheat, rice, maize, potatoes, millet, and barley. Nevertheless, we do have the means to re-introduce variety into our meals. As hard as it might be to believe after having read this far, vilifying carbohydrates is not the intention of this article. In fact, one would be hard-pressed to avoid them entirely, and would likely lose many essential nutrients in the process.

When it comes to correcting course, our bodies are more like container ships than motor boats.

Instead, the aim should be to tip the scales back in favor of a more balanced diet, in which whole grains and starchy vegetables play a contributing, rather than a dominant, role. Variety should be the guiding star when it comes to structuring our menus. The vegetable aisle, for instance, should not be visited briefly in search of a colorful side for tomorrow’s dish, but should instead be visited for its own sake — and amply sampled.

Furthermore, food labels should not be regarded as exclusive reading material for health-nuts. We give ourselves too much credit when guesstimating the calories in our food. Our bodies, on the other hand, are spot on. It’s only too bad they don’t come pre-installed with an early warning system for when they have taken in more than they need, since, when it comes to correcting course, they are more like container ships than motorboats. Labels, therefore, help us know both what and how much we are actually putting inside our bodies before potentially incurring the cost of going overboard.

Photo by Food Photographer David Fedulov on Unsplash

Besides the obvious nutritional gains, the benefits of a diet more true to our omnivorous roots are twofold. First, it achieves satiation at a lower caloric threshold, owing to the generally lower calories and higher fiber content of the ingested foods, which slows their breakdown during digestion. Secondly, it promotes a healthier, more diverse gut microbiome. That is, the conglomeration of microorganisms inhabiting our gastrointestinal tract, which play an important role in nutrient and mineral absorption, synthesis of enzymes, vitamins and amino acids, as well as the production of short-chain fatty acids, which reduce gut inflammation, among other things.

If old habits die hard, it’s understandable that ancient ones will take more than wishful thinking to amend. Thankfully, we are armed today with both the knowledge and the means to turn back the wheel, even if only just a bit, and come one step closer to creating a world within that’s as prosperous as the one our ancestors plowed the way for without.