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Reviewed by:
  • The Evolution of Obesity
  • Wendy Mitchinson, Ph.D.
Michael L. Power and Jay Schulkin. The Evolution of Obesity. Baltimore, Maryland: The Johns Hopkins University Press, 2009. ix, 392 pp., $40.00.

Books on obesity and the obesity epidemic have become best sellers as physicians, researchers, nutritionists, politicians, economists, and individuals try to come to terms with the nature of obesity, its causes, and the best way to respond to it. Michael L. Power and Jay Schulkin do not address the latter, but rather take an evolutionary approach to biology to better understand the complex nature of our bodies and how they have adapted over the millennia. Both are researchers at the American Congress of Obstetricians and Gynecologists (Schulkin is its research director) and, unlike many of writers on the topic who focus on the obesogenic environment in which we live, their interest is how the biology of our bodies came to be, arguing that if we are to overcome the obesity crisis, then we must understand that there is no silver bullet of cure.

Their purpose is clear: to account for the relatively recent change in our shape and size and to do so by focusing on the evolution of the species. For historians, the idea that we take the past with us will not be new; it will not even be new for most biologists and evolutionary specialists. New for most readers, however, is Power's and Schulkin's crucial point that the past that we carry within our bodies was adaptive so that various parts of the body in their most microscopic essence became multi-purpose. As they argue "molecules that regulate physiology and behavior are ancient and have been co-opted to perform multiple functions that vary with tissue, stage of development, and the conditions of the internal milieu" (viii). Essentially, they examine how biologies and environments have interacted over time. Part of that interaction has allowed humans to absorb fats easily compared with other primates and to process more food than we now need.

Power and Schulkin argue that our present-day obesity crisis is the consequence of a "mismatch" between our biology and the environment in which we live. While not a new theory (think of the so-called thrifty gene), it is in the detail of its explanation that their study excels. They take the reader on a whirlwind tour of anthropological and biological research. Whereas most animals feed, humans eat meals with one another resulting in a vast array of behavioral customs. From this volume we learn how eating behavior is influenced by endocrine and metabolic signals, how and why we anticipate eating, the differences between satiation and satiety and how each works, the biology of fat, gender differences, genetic influences, racial differences (which are not as clear as others have believed [End Page 125] because of ancestral genetic mixture), and influences in utero. If at times the detail is overwhelming, the thrust of the book is always evident: "We evolved on the savannahs of Africa; we now live in Candyland" (110).

Solving the obesity "crisis" will involve more than eating less and exercising more. What Power and Schulkin want us to understand is that it will require us modifying the kind of societies in which we live and working against years of biological adaptation. There is no quick fix. They remind us that obesity is not about weight, but fat. We may hate fat, but we need fat in order to survive and our relatively large brains need fat to function. Human newborns (with the exception of hooded seals) are the fattest newborns, and that fat is crucial for brain development. It is also an advantage for survival when infants are exposed to various pathogens, a result of humans living in a more densely populated way compared with other species.

Anyone looking at the history of research on obesity will be struck by certain themes that Power and Schulkin share with their predecessors. They are excited by what they see as the explosion of knowledge about the body and its workings. Such excitement is a research-based one, not a clinical one, and has long existed with both physicians and...

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