Man originally was a hunter-gatherer and our organism is therefore designed to profit as much as possible from periods of abundance in anticipation of unavoidable food shortages. As long as the vast majority of mankind remained chronically underfed, this wasn’t a problem. Fat people were oddities – King Henry VIII of England, rotund Chinese mandarins and adipose oriental potentates spring to mind –, much envied since their large girth was a symbol of their wealth. But with the advent of the Industrial Revolution, the mechanization of agriculture and the development of efficient pesticides, a growing percentage of Mankind started to eat its fill… and sometimes more than it, and now we face the opposite problem. Our metabolism’s very efficiency puts us at risk of overweight, obesity and prediabetes. And today, obese human outnumber malnourished ones.
In May 2012, the European Obesity Congress wondered whether our society should be deemed “obesogenic” or “diabetogenic”. When one considers the evolution of our contemporaries’ average weight, or their energetic intake, the answer might well be yes… In 1970, Americans ate 2,200 calories per day, i.e. the recommended daily intake for an adult; now they eat 2,700 calories.
Healthy eating is more expensive
This phenomenon is exacerbated by economic factors. According to a recent American survey, following the Surgeon General’s recommendations in order to eat “healthily” costs at least 400 extra dollars per year. In short, one dollar of crisps is more filling than one dollar of carrots… No wonder then that along depression and other psychiatric disorders, or severe high blood pressure, type 2 diabetes should strike more than twice as often the most badly off populations.
“Social jetlag” harms the waistline
Modern schedules also contribute to the disruption of our metabolism by leading to a chronic discrepancy between our biological clock and our daily schedule, so that we are permanently “jetlagged”. A 10-year study by researchers from the university of Munich published in Current Biology (Till Roennenberg and al.) has identified a “social jetlag” in our contemporary societies. It results in lack of sleep, obviously, but also, and above all, health disorders. People with social jetlag are more likely to be smokers, to drink alcohol and a lot of caffeine, and also to become overweight and/or obese.
Environmental hazards promote weight gain
Environment ranks high among the lifestyle factors apt to promote overweight, obesity, prediabetes and type 2 diabetes. The French Scientific Academy report “Hormones, santé publique et environnement” (Hormones, public health and environment) emphasizes the impact of modern polluting agents and hormones used in animal husbandry on health, and particularly on the tendency to develop diabetes, obesity and hormone-sensitive cancers. As the coordinators of this survey Prof. Edwin Milgrom and Prof. Etienne-Emile Beaulieu explain, environmental changes lead to the “appearing or the worsening of new pathologies” because our hormone regulating systems lack time to adapt to the situation. A University of Columbia (New York) survey, conducted on 702 pregnant non-smoking mothers aged 18 to 35 years old, has indeed shown that children born to women exposed to atmospheric pollution during their pregnancy may be at increased risk of childhood obesity. Aged seven, the offspring of the most exposed mothers displayed up to 2.4 extra fat kilograms, with an obesity risk multiplied by 2.20 (and by 1.79 by the age of five). The survey notably stressed the hazards of the polycyclic aromatic hydrocarbons (PAHs) that we absorb on a daily basis as every combustion process (even that of a scented candle) produces PAHs apt to contaminate our environment and our food, particularly seafood. And these PAHs may disrupt the lipolysis process (transformation of body fat into energy), so that the body will prove reluctant to destock fat, especially children’s bodies.
In the last few decades, health scandals involving phthalates, parabens and other chemicals used in plastic containers and cosmetics, all suspected of impairing male fertility and/or causing breast cancer, have raised the public’s awareness of endocrine disruptors. These chemical hidden in many consumer goods to which we are exposed on a daily basis affect the production or the efficiency of the hormones that regulate our endocrine system, with consequences such as reduced fertility, alteration of the reproductive function and growth disorders. Disruptions have been noticed in almost all animal species, with anatomic, reproductive, immunologic and even behavioral anomalies. The Baltic grey seals almost became extinct in the 1970s because the insecticide DDT and the PCBs used on trees made them infertile. Nowadays, the estrogen steroids spilled in our rivers have turned an estimated third of the roaches into hermaphrodites, while their spermatozoids’ mobility has dropped by 50 to 75%. As for female mollusks, which are very sensitive to water pollution as they are poorly armed to eliminate chemical pollutants, they tend to develop male features when exposed to tributyltin (TBT), a component of the paints used on boat hulls. And the whole planet is endangered, as the ocean currents spread the pollutants: in the Kerguelen islands, thousands of miles away from industrial and farming areas, the trout show as much organochloride pollution as eels caught in the delta of the Rhone!
That is to say endocrine disruptors put all the natural ecosystems in jeopardy. And although we are aware of their noxious effects, we do not know their full impact on nature, animal and/or human populations, especially since they are harmful even in very small concentrations, they sometimes have a latency period and their impact may last several generations.
We live longer but nothealthier
All this might explain why although the overall life expectancy rises, the Healthy Life Years indicator (the years we can expect to live in good health) rather tends to fall in Western countries. It seems quite likely that our lifestyle and diet habits are to blame. The followers of the “Paleolithic diet”, a concept born in the 1970s and popularized by several dieticians and anthropologists, go further. Their reasoning is based on a simple – even simplistic – premise: as, apart from a few details, our genome has not much evolved since Cro-Magnon appeared, returning to the diet favored by our forebears some 40,000 years ago should help us recover these hunter-gatherers’ svelte physique and hardihood, meanwhile protecting us from so-called “civilization” diseases like high blood pressure, diabetes, cardiovascular disorders, obesity, etc. Unfortunately, it does seem unlikely that these disorders linked to very recent (a few decades) lifestyle changes should be ascribed to our ancestors settling down and changing diet when they adopted agriculture and animal husbandry over ten thousand years ago… Moreover, the lifestyle of Paleolithic men was very different from ours, not only diet-wise, and anyway, with a life expectancy of 25 years; they seldom reached middle age and its inconveniences!
This theory also implies a rejection all the epigenetic aspect of our adaptation, that which has allowed us to prosper under various climates and in various environments. However, just as migrant populations are more likely than native ones to develop metabolic or weight disorders when eating the same diet, it makes sense to stay clear from diet fads that encourage the immoderate embracing of new foods unknown from us and our forebears. Let us take the example of quinoa: it is much praised, and deservedly so, but we have not yet expressed the genes necessary to adapt to eating large amounts of it. Therefore, as a safety precaution, we should refrain from making it (or any other “new” food) a basis of our diet until its long-term innocuousness has been proven.
Even though our modern Western lifestyle may justly be called obesogenic, falling prey to excess weight and metabolic disorders is not a fatality. The key to a better health doesn’t lie in a return to Paleolithic mores or in the ditching of our staple foods for new “super foods”. We should however be aware of the harmful effects of pollution and endeavor to minimize our exposure to it.

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