The Failure of Diet-Centrism
To the editors:In his essay, Vaclav Smil offers an engaging analysis supporting the diet-centric argument that obesity and cardio-metabolic diseases are “consequences arising from a surfeit of food.” Though Smil’s elegant exposition is worthy of perusal and extended discourse, his conclusions evoke the adage that “there is always a well-known solution to every human problem—neat, plausible, and wrong.”1
I sincerely appreciate Smil’s scholarship, insights into omnivory, and accurate depiction of my work on the near-meaninglessness of nutrition research.2 In this letter, I will attempt to explain why his solution entailing a “curtailment of the oversupply of food” is emblematic of the diet-centric dogma that fails to address the fundamental causes of obesity and cardio-metabolic diseases. That is, the nongenetic inheritance and evolution of mammalian metabolic phenotypes. Before delving into the details of how nongenetic evolutionary processes have led to the twin epidemics of obesity and metabolic diseases, it is important to examine a number of facts and arguments that constrain, and in many instances refute, Smil’s diet-centric arguments, conjectures, and solutions.....MUCH MORE
Food Supply Is Irrelevant
It should be obvious that a large food supply does not inevitably lead to obesity. After all, a large body of water does not inevitably cause drowning and an abundance of atmospheric air does not automatically lead to hyperventilation. Just as one individual drowns in a bathtub while another swims easily in an ocean, obesity is surging in nations with relatively small food supplies, such as Botswana and Nigeria. At the same time, many individuals in nations with a surfeit of food, such as Switzerland and Norway, remain lean and healthy.3
The size of the macro-environment—that is, the body of water, air supply, and food supply—is not relevant, nor even related to these outcomes. There is no valid relationship between a nation’s food supply and its levels of obesity and metabolic diseases. Compared to Switzerland, New Zealanders spend a greater percentage of household income on food and have a smaller per capita food supply.4 Nonetheless, New Zealanders have an obesity prevalence approximately 250% greater than the Swiss. From 1910 until the 1960s, the per capita food supply in the US decreased from 3,500 calories to 3,100. This reduction was accompanied by an increase in body mass.5 Both logic and empirical data refute the notion that a surfeit of food, whether as a result of lower costs or a larger supply, is a causal factor in obesity and metabolic dysfunction.
The Problem Is Physiology, Not Food
As my work has shown, it is not what one eats and drinks that causes obesity and cardio-metabolic diseases, but what one’s body does with the foods consumed.6 Known as nutrient-partitioning, this physiologic process determines how many calories one eats and drinks, and whether the body burns or stores those calories as fat or muscle.
An individual’s metabolic phenotype determines both habitual caloric consumption and the metabolic fate of consumed fats, proteins, and carbohydrates—the nutrient-partitioning building fat or muscle mass. The amount and effects of consumed foods and beverages, as well as the concomitant risk of obesity and cardio-metabolic disease, are entirely dependent on the metabolic phenotype and nutrient-partitioning of the individual in question. It is well-established that different people can eat and drink the same foods and beverages, yet have widely disparate metabolic responses.7 Diet-centric arguments ignore individual differences in metabolic phenotype and the resulting fate of consumed foods and beverages.
Increased Obesity in People and Animals
Over the past five decades, incremental increases in body mass, obesity, and metabolic dysfunction in human populations have occurred in synchrony with parallel trends in laboratory, farm, feral, and companion animals, such as dogs, cats, horses, moose, mice, and monkeys.8 Given that these diverse populations live in disparate food environments and vary in their nutritional requirements, the data is suggestive of a global evolution in mammalian metabolic phenotypes....
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The Hidden Costs of Good Eats
....MORETo the editors:Vaclav Smil’s “Good Eats” is a brilliant and timely essay that should lead us to reflect upon the directions in which modern society is currently developing. I would like to take Smil’s argument a step further and ponder the implications that follow from the entanglement between endosomatic and exosomatic metabolism in modern society. Endosomatic metabolism refers to the food, energy, and nutrients metabolized inside the human body to sustain its physiological activities. Exosomatic metabolism refers to the energy and material metabolized outside the human body to sustain the technical and economic activities guaranteeing our food system. These two forms of metabolism coexist within human society and are profoundly interrelated.1 In the modern world, we never eat alone. Each bite we take cannot take place without another form of consumption: the energy and materials devoured by the machines and technology that sustain our economy. Many of the uncomfortable facts flagged by Smil are related to this forced commensalism between humans and machines. Consider the following four arguments:
- Exosomatic metabolism has come to dominate the economy, rendering agriculture increasingly irrelevant in today’s society. In developed countries, the agricultural sector contributes a negligible share of GDP and no longer has much influence over the processes involved in the production and consumption of goods and services. Rural areas do not contribute significantly to the economic development of a country and are reliant on subsidies. In post-industrial economies, exosomatic organs, such as production machinery and distribution processes, play an essential role in feeding the urban population as cheaply as possible. The status of agriculture has been reduced to a specialized function of these organs. In this new framework, the farmers have no choice but to follow patterns of urban demand. Their labor having already largely been replaced by machines, the output of farmers is now replaced with imports if it fails to meet the expectations of urban society.2
- The affordability of food—the supply of endosomatic inputs—for urban elites must be contextualized in relation to a society’s exosomatic metabolism. The transformation of the agricultural sector has increased food production at the expense of farmers, who are gradually being eliminated from the workforce. Farmers do not represent a significant share of the paid work sector in any developed country.3 Those driving the economy have found that they can produce much more added value using machines. Adding value guarantees higher incomes, increasing the amount that people can afford to spend on food. But, as illustrated by Engel’s law, food affordability is only a relative measure. The fraction of income spent on food in rich countries is low—below 14% of total expenditure. This amount is still at least five times higher than in the developing world.4 The affordability of food in developed countries does not mean that food is cheap. Their ability to absorb higher costs associated with food production means that these societies can use more machines and spend more on food and other goods and services.
- Food has a different meaning for today’s urban elites than it did in traditional societies. The value of food in prosperous societies is dependent on two factors: convenience and social status. In developed countries, the preparation of food is now a matter of minutes, whereas 70 years ago it required hours. This increased level of convenience has allowed for an influx of women into the workforce, boosting the economic performance of society’s exosomatic metabolism. The social implications associated with consuming a particular cuisine or product are a greater determinant of value than quantity alone. When choices made by consumers are influenced, for the most part, by convenience and social status, preservation of the original nutrients becomes less of a priority and nutrition is neglected as a result....
Okay, maybe not so much "rejoinders" as expounding upon and contextualizing.
