What Metaphor?

The Sixth Stage as a practical metaphor for pursuing your health goals (or, how to translate stuffy academic theories into real-world plans of action)

You need not be an academic or answer to “professor” to use theory as a guide in your own life. No degree, license, or certification is required.

To that end, it’s unfortunate that the manner in which many academics and researchers discuss or describe theory—such as in the peer-reviewed literature—makes it seem like a black box. In the social sciences, in particular, theory is not a black box—it’s simply a description of how we think certain aspects of the world work. It’s like a story. That’s it. Sometimes abstract, yes. A black box, no.

I have spent many hours struggling to deconstruct the cryptic academic language that researchers use to discuss the theories that drive their work. It’s a frustrating endeavor until, that is, you realize just how applicable that seemingly cryptic language is to your own life.

[Side note: Despite my somewhat critical tone, I strongly believe that by continually developing, testing, and refining theories, researchers provide conceptual clarity to the everyday notions, perceptions, and ideas that many of us have trouble articulating ourselves. I can’t overemphasize the importance of this because it provides the basis for moving knowledge forward—the very knowledge that we all depend on to make sense of the world around us.]  

On that note, enter three theories that, by the end of this post, will mean something to you:

  • the Demographic Transition,
  • the Epidemiologic Transition, and
  • the Nutrition Transition.

[Side note: Much of the remainder of this post relies on conveying important points from  the peer-reviewed literature (full citations are listed at the end). Stick with it—my goal is to prove to you how these seemingly abstract academic blatherings really do frame our current health-related context.]

The Demographic Transition Theory

According to Kirk (1996), the theory of the demographic transition “states that societies that experience modernization progress from a pre-modern regime of high fertility and high mortality to a post-modern one in which both are low.”


By way of example, notice how the population pyramids for the United States and the United Kingdom differ from the population pyramid for Sub-Saharan Africa.

[Side note: More translations to come.]

The Epidemiologic Transition Theory

In his classic 1971 manuscript introducing the theory of the epidemiological transition, Omran provides an intuitive definition of epidemiology as “the study of what comes upon groups of people.”

More specifically, “epidemiology is concerned with the distribution of disease and death, and with their determinants and consequences in population groups.”

Needless to say, these are complex phenomena and, at the time, Omran acknowledged that existing theories simply didn’t capture the full spectrum of relevant demographic, biological, sociological, economic, and psychological drivers and consequences of transitions in population health.

To overcome these limitations, he developed and proposed the theory of the epidemiologic transition: “Conceptually, the theory of the epidemiologic transition focuses on the complex change in patterns of health and disease and on the interactions between these patterns and their demographic, economic and sociologic determinants and consequences.”


There are five propositions:

Proposition 1
“The theory of the epidemiologic transition begins with the major premise that mortality is a fundamental factor in population dynamics.”


Proposition 2
“During the transition, a long-term shift occurs in mortality and disease patterns whereby pandemics of infection are gradually displaced by degenerative and man-made diseases as the chief form of morbidity and primary cause of death.” This shift occurs across three stages:

  • the first stage: the age of pestilence and famine,
  • the second stage: the age of receding pandemics, and
  • the third stage: the age of degenerative and man-made diseases.

As you can see above, during the age of pestilence and famine, if you manage to survive plagues and epidemics of infectious diseases, you’ll still die at a young age from malnutrition. You definitely won’t live to see the age of 40.

During the age of receding pandemics, environmental and biological causes of death wane. Omran notes “one outstanding example is the recession of plague in most of Europe toward the end of the seventeenth century. The reasons for this recession are not fully understood, although the mysterious disappearance of the black rat may have been a contributing factor.” Living standards, public sanitation, hygiene, and nutrition improve, but you’ll be lucky to live to see the age of 50.

During the age of degenerative and man-made diseases, living standards, hygiene, and nutrition continue to improve. Advancements in medicine and public health, including immunizations and treatments, extend life expectancy to beyond 70 years. In the face of chronic diseases, mental illness, addiction, accidents, and pollution problems, morbidity—not mortality—becomes a defining marker of population health.

Proposition 3
“During the epidemiologic transition, the most profound changes in health and disease patterns obtain among children and young women.”


Proposition 4 
The shifts in health and disease patterns that characterize the epidemiologic transition are closely associated with the demographic and socioeconomic transition that constitute the modernization complex.”


Proposition 5
“Peculiar variations in the pattern, pace, the determinants and the consequences of population change differentiate three basic models of the epidemiologic transition: the classical/western model, the accelerated model, and the contemporary or delayed model.”

In other words, in terms of timing, this is not a one-size-fits-all formula. Not all populations proceed through the stages of the epidemiologic transition at the same pace. By way of example, the U.S. and western Europe typify the classical model, while Japan’s transition represents the accelerated model, and most countries in Latin America and Africa represent the delayed model.

The three graphs below provide a crude visual depiction of each model (individual scales for each axis are omitted because the point is to simply note the different patterns).

Green line = population level
Red line = crude death rate
Blue line = crude birth rate

X-axis: Time in years from 1790 to 1970




The Epidemiologic Transition Continues…The Fourth Stage

About 15 years following Omran’s original publication of the epidemiologic transition theory, Olshansky and Ault (1986) declared a fourth stage—the age of delayed degenerative diseases. During the fourth stage, “the major degenerative causes of death that prevailed during the third stage of the transition remain with us as major killers, but the risk of dying from these diseases is redistributed to older ages.”

Marked by lower rates of mortality from cardiovascular diseases—owing to smoking cessation programs, effective blood pressure control, and technological advances—the fourth stage began in the U.S. by the mid-1960’s.

In other words, chronic diseases—diabetes, heart disease, cancer, etc.—are still the leading causes of death. With the help of medical advancements, individuals simply are able to live longer with these diseases.

Finally, the Fifth Stage of the Epidemiologic Transition

By the early 1990’s, the U.S. reached what Gaziano (2010) describes as the age of obesity and inactivity, “marked by an alarming increase in overweight and obesity and continued decreases in physical activity.”

“Despite the many advances in preventive medicine and treatment that reduced cardiovascular disease…the age of obesity and inactivity emerged to threaten the progress made in postponing illness and death to later in adult life spans.”

Today, as Swinburn et al. (1999) note, “people struggle against environments which increasingly promote a high energy intake and sedentary behaviors…the ‘obesogenicity’ of modern environments is fueling the obesity pandemic.”


Inevitably, the Nutrition Transition Occurs

The nutrition transition theory, according to Popkin and Gordon-Larsen (2004), proposes that “modern societies seem to be converging on a diet high in saturated fats, sugar, and refined foods but lower in fiber—often termed the ‘Western diet’—and on lifestyles characterized by lower levels of activity. These changes are reflected in nutritional outcomes, such as changes in average stature, body composition, and morbidity.” Over time, populations transition from succombing to the dangers of food scarcity to overabundance.


A Recap

By now, it’s obvious that the phenomena described by all three theories occur, more or less, simultaneously.


Some good news…

If you’re reading this, chances are that you’re fortunate enough to live in a part of the world that is late in the demographic and nutrition transition games. Rejoice—mortality rates are low, life expectancy is high, and food and research knowledge are plentiful.

Some bad news..

If you’re reading this, chances are that you belong to a population that’s grappling with the fifth stage of the epidemiologic transition, the age of obesity and inactivity. Beware—food is plentiful (all of the wrong kinds) and research knowledge is growing exponentially (more on this later).

But, things can and do change…

The Sixth Stage

It’s a metaphor, really, for what’s next. What will be your Sixth Stage?


From the literature:

Gaziano, J. M. (2010). Fifth phase of the epidemiologic transition. JAMA, 303(3), 275-276. 

Kirk, D. (1996). Demographic transition theory. Population Studies, 50(3), 361-387.

Olshansky, S. J. & Ault, A. B. (1986). The fourth stage of the epidemiologic transition: the age of delayed degenerative diseases. The Milbank Quarterly, 64(3), 355-391.

Omran, A. R. (1971). The epidemiologic transition: a theory of the epidemiology of population change. The Milbank Memorial Fund Quarterly, 49(4), 509-538. 

Popkin, B. M. (2002). An overview on the nutrition transition and its health implications: the Bellagio meeting. Public Health Nutrition, 5(1A), 93-103. 

Popkin, B. M. & Gordon-Larsen, P. (2004). The nutrition transition: worldwide obesity dynamics and their determinantsInternational Journal of Obesity, 28, S2-S9. 

Swinburn, B., Egger, G., & Raza, F. (1999). Dissecting obesogenic environments: the development and application of a framework for identifying and prioritizing environmental interventions for obesity. Preventive Medicine, 29(6), 563-570. 

Leave a Reply

Your email will not be published. Name and Email fields are required.