THE OMNIVORE'S DILEMMA The Evolution of the Brain and the Determinants of Food Choice

More than 72 million Americans, over a third of the population, are obese. In the past three decades, the rates of obesity in adults have doubled, and rates in children have tripled. Obesity rates have markedly increased among all segments of society, including those defined by age, sex, race, ethnicity, socioeconomic status, education level, and geographic region. Michael Pollan (2006) argues that the obesity crisis is due to the abundance of foods now available to satisfy the omnivore's dilemma, the desire for dietary variety required to meet energy requirements paired with the often fearful and perilous search for new foods. The abundance of food is an important factor in the obesity problem, but the solution to this perplexing riddle is more complex and is buried in our evolutionary history. A biocultural perspective, which highlights coevolutionary processes, is most useful for understanding humans' dietary and nutritional adaptation to changing social and physical environments. In our early evolution, the evolving body—with an expanding brain, lengthening small intestine, and shrinking large intestine—required nutritionally dense foods. Our current pattern of eating reflects the way in which Homo sapiens evolved and resolved the omnivore's dilemma. The resolution of the omnivore's dilemma lies in the development of cuisine to mediate this biological conflict. Cuisine defines which items found in nature are edible, how these substances are processed into food, how the foods are flavored, how and with whom we eat, and the rules of eating—the code of etiquette. With the transition to primary food production during the Neolithic, the variety of foods dramatically decreased. The need for variety was met by creatively experimenting with food preparation, despite the availability of limited ingredients. The shift toward large-scale agriculture in the past century led to an overall decline in human nutrition by reducing dietary breadth. More recently, industrialization of the food system has made an overwhelming abundance of inexpensive, high-density foods (sugar and fats) available to populations in some areas of the world. The disjunction between the small amount of physical energy they expend to obtain significant numbers of calories has created the modern obesity epidemic.