I’ve just finished reading Richard J. Johnson’s 2022 book, Nature Wants Us to Be Fat. Johnson is a practicing kidney physician (a nephrologist) who – like Jason Fung – also conducts research on the effects of the modern Western diet on human health (and specifically the kidneys). Occasionally, Johnson produces semi-technical books for lay readers that summarize the results of his and his co-workers’ ongoing research and current thinking.
In 2009 he published The Sugar Fix, detailing the negative effects of fructose and other dietary elements (and their biochemical byproducts) on human health. Johnson’s 2012 book, The Fat Switch, elaborated on his initial theme, bringing in several lines of evidence that suggest that the diet-related biochemical mechanisms that cause problems for modern people were originally evolutionarily adaptive. His latest (2022) work, Nature Wants Us to Be Fat, is a scientifically careful, well-written, and well-organized update of the still accreting working hypothesis that has organized much of his professional life.1
Johnson’s basic working hypothesis is that the human ability to store large amounts of fat has been, much more often than not, an extremely critical survival trait. Unfortunately, the various environmental triggers that episodically accelerated human fat storage in the past now influence most of modern humanity almost constantly. As a result, obesity and the non-communicable diseases that typically accompany it (e.g., hypertension, atherosclerosis, diabetes, heart disease, kidney disease, liver disease, metabolic syndrome, increased cancer rates, and certain behavioral difficulties – i.e., ADHD and bipolar disease) have become common chronic problems in our industrialized and urbanized cultures.
Johnson posits that at different times during human evolution, climatic shifts caused human gene lines to adapt to significant changes in their nutritional environment. These (so far) permanent genetic changes have locked human nutritional biochemistry into rigid, limited patterns of involuntary response to outside nutritional influences. Because the modern diet now exposes much of humanity to long term caloric excess – especially exogenous and endogenous fructose (fruit sugar), many people are now locked into an enduring process of fat gain that, if almost any given person lives long enough, eventually develops into health-degrading chronic illnesses.
For example, Johnson reports that there is genetic evidence that the primate line containing humanity lost the ability to synthesize its own vitamin C about 65 million years ago, following the dinosaur-killing “impact winter” created by the Chixculub Meteorite collision with the earth. He explains that the low vitamin C cellular levels consequent of this genetic change would have coerced the surviving primate lines into developing a dietary preference for eating seasonally available plant fruits. Plant fruits contain not only vitamin C but high concentrations of the most efficient fat-forming sugar, fructose. Given that ripe fruits highest in fructose contain relatively low levels of vitamin C, the primates of that time would have been driven by their vitamin deficiency to gorge and thereby grow fat on that fruit in order to unconsciously meet their dietary requirements for essential vitamin C. This old inherited human hunger for sweets and fruits endures into these modern times with an industrialized food production system that makes fruits and high fructose corn syrup-sweetened soft drinks foods available all year long — allowing constant and excessive satisfaction of our primate sweet tooth.
Similarly, Johnson explains that, as the earth gradually started cooling off in the late Cenozoic, the gene for the enzyme uricase died out entirely by 15 million years ago (Miocene) in the primate lineage. When present in animal body cells, uricase decreases the concentration of uric acid. With the genetic loss of uricase, primates began to exhibit high tissue concentrations of uric acid. Because heightened uric acid strongly depresses basal energy expenditures of animals, more of any food eaten will be converted to and stored as fat. The energy conserving loss of this uric acid degrading enzyme was cemented into genetic place by the reduced availability of fruits and other carbohydrate food sources upon the Eocene-Oligocene start of the still ongoing Late Cenozoic Ice Age: when food was scarce, it used to pay for more of its calories to be set aside as body fat for the hungrier months of each year.
Again, now that most of humanity meets with food abundance – especially high fructose corn syrup enriched processed foods and drinks – the old ancestral triggers of simultaneously accelerated body fat storage and depressed energy expenditure are always active.
There is considerably more to the model of the evolutionarily developed human dietary appetite system outlined by Johnson and his co-workers, but all of the rest of known controlling variables to human appetite causing obesity and other health problems identified in Nature Wants Us to Be Fat are shown in the illustration below taken from the book:
As is usual for popular reading concerning human diet, the last sections of Johnson’s book recommend general and specific tactics for reducing personal obesity and avoiding its negative health effects in the face of plenty. Most of these recommendations are not unique, and generally are in agreement with the basic tenets of the Mediterranean and low carb diets. Johnson’s latest text is unique, however, in that it indicates how human evolutionary history explains the apparent origins of humanity’s current difficulties in controlling its biologically-determined strong food appetite when faced by the abundance afforded by the modern food supply system.
Johnson’s 2022 book shows clear signs that he read and took to heart the Amazon.com-posted reader comments and criticisms attached to his 2009 and 2012 writing efforts. That’s an interesting unintended side benefit of the Amazon system of retailing: long term writers can obtain direct feedback from a large sample of their readers. This facet of the new social media will, I suspect, facilitate increased writer-reader communication efficiency over the long run.