The hungry brain in the 21st century: Challenges and opportunities for health

On October 12, I’ll be speaking at the Evolutionary Nutrition conference and Staffan Lindeberg memorial in Lisbon, Portugal.  I was asked to write a one-page abstract of my talk, which I have reproduced below.

The world is undergoing a striking transformation of health and demographics that has been called the “epidemiologic transition”. This term was coined by Abdel R. Omran in 1971, who wrote “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.” It has been forty-six years since Omran wrote these words, yet our ever-expending evidence base continues to support his hypothesis.

Most notably, the Global Burden of Disease project has documented that people in low-income countries continue to die primarily of infectious diseases, accidents, and violence. These are the scourges of our ancestors. In contrast, people in high-income countries have mostly overcome the threat of infectious disease, accidents, and violence, yet we face a new set of scourges: Omran’s “man-made diseases”, more commonly called noncommunicable diseases. These include obesity, diabetes, coronary heart disease, stroke, most heart failure, kidney failure, gout, some cancers, and many more. Although overall mortality is falling as global economic development proceeds, many people in affluent nations live with debilitating noncommunicable diseases that limit their potential for health and well-being. And low-income countries are severely affected by epidemics of noncommunicable disease as they rise to greater affluence.

Studies of traditionally-living cultures suggest that most common noncommunicable diseases, such as obesity and severe coronary heart disease, are evolutionary mismatch disorders, meaning that they result from poor compatibility between our ancient genomes and the modern industrial diet and lifestyle. Yet what is the nature of this mismatch? It is undoubtedly complex, however I will argue that one element of it is as simple as it is influential: Energy excess. Consuming more energy than one expends is well-established to cause obesity, yet evidence also strongly suggests that energy excess is the primary nongenetic cause of type 2 diabetes, and an important contributor to cardiovascular disease, certain cancers, orthopedic problems, and many other common ailments.

To understand why we engage in behaviors that lead us to energy excess, we must first acknowledge that the brain is the source of all behavior, that it evolved in a specific range of contexts, and that the inclinations we have today are a result of that process. Our ancestors evolved in a context in which they had to acquire energy from an environment that does not easily give it up. As a result, they developed learning and motivation systems that attempt to maximize their energy return rate by seeking calorie-dense foods that require the least time and effort to obtain, and avoiding unnecessary physical activity energy expenditure. In affluent countries today, nonconscious brain circuits continue to implement the rules of this obsolete survival game, and they drive most of us to energy excess. They are extremely persuasive due to the key role they played in the reproductive success of our ancestors, explaining why most of us overconsume food despite understanding the serious long-term consequences.

How do we solve the problem of energy excess when it emerges from human nature itself? I propose that instead of fighting the nonconscious brain circuits that drive our food intake, we understand them and provide them with diet and lifestyle cues that align them with our goals of leanness and health. In this way we may avoid exchanging the scourges of our ancestors for the scourges of modernity.

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