FAYETTEVILLE, Ark. - Fad diets that restrict the types of food we eat may actually jeopardize our overall health. Such weight loss schemes are based on the erroneous notion that eating only a few specific foods can lead to better health. On the contrary, says University of Arkansas anthropologist Peter Ungar - humans evolved to consume the widest possible range of foods, and limiting that variety can lead to serious health risks.

Rather than whittling your diet down to a select group of foods, a healthier approach to nutrition is to expand the variety of foods you eat. After all, says Ungar, that’s what four million years of evolution has designed the human body to do.

"Americans assume that their diets are varied because of the seemingly infinite array of foods available to us," Ungar said. "But if you look at the average American diet, it consists mainly of fat and starch. Occasionally, we throw in some tomatoes.

"Diets that purport to solve that problem by cutting out entire categories of food are taking the wrong approach," he added. "The modern risk is that our diets aren’t varied enough."

Experts across the nation agree. In a new book titled "Human Diet: its Origin and Evolution" Ungar and co-editor Mark Teaford of Johns Hopkins University gathered leading experts in health, nutrition and human evolution to produce a comprehensive review of the human diet. Published by Bergen & Garvey, it represents one of few books to address the topic of diet using insights and evidence from multiple fields.

By combining the expertise of physicians, anthropologists, nutritionists and paleontologists, the book examines human diet from the eating habits of our earliest ancestors to the diet-related health problems that plague our world today. Each chapter cites evidence from the latest research in those fields, and each contributes to the overall message: that human beings evolved to eat the most varied diet of any species and that the limited nature of our modern diet can lead to chronic health problems.

In the preface to the book, Ungar and Teaford write that "diet changes have far outstripped the capacity of genetic evolution to keep pace with changes in what we eat today." The discrepancy between our modern eating habits and the metabolic functioning of our bodies has given rise to such diseases as diabetes, cancer and heart disease. Further restriction of food intake, as prescribed by fad diets, has been shown to promote kidney failure, enlargement of the pancreas and iron deficiency.

"Human Diet" begins with two chapters that examine the link between diet and health. In the first of these chapters, a physician of evolutionary medicine and two of his colleagues assess how excessive consumption of saturated fats, simple sugars and sodium impact human health. They then compare the nutritional content of our modern diet to that of our ancestral diet.

In the second chapter, a bioarcheologist examines the shift from hunter-gatherer societies to agricultural settlements. He states that the effects of that transition on diet content immediately resulted in a decline in health. Bones and teeth from that transitional period show increased infection, dental disease and physiological stress. The researcher then emphasizes that the agricultural foundation of our modern food supply continues to deteriorate human health.

While the opening chapters of "Human Diet" assess modern health concerns, subsequent chapters trace the trail of evidence back, hoping to illuminate the health and habits of human ancestors. The authors of these chapters - including Ungar and Teaford - attempt to reconstruct early hominid diet through observation of modern hunter-gatherer societies and primate models, or through evidence found in the fossil record.

By understanding the diet of our earliest ancestors, these researchers hope to identify how modern eating habits have diverged and to assess the physiological consequences of that divergence. These latter chapters drive home the point that diet has profoundly influenced the design and function of the human body.

In an unpredictable environment, the ability to consume and digest whatever foods were available meant the difference between survival and extinction for many species. Early hominids coped with an uncertain food supply by adapting to eat as many different foods as possible. These adaptations included changes in tooth and jaw morphology, in digestive functioning and metabolic processes. Contributors to the book explore the development and consequence of each of these adaptations.

But the features that allowed our ancestors to adopt such a varied diet were not just physiological. They were also mental. According to Ungar, the capacity for innovative thinking led to tool use and methods of external food preparation. By cooking and cutting, early hominids gained access to foods that otherwise would have been inedible.

"We are unique in the broad spectrum of foods we take. Primates have a much broader diet than other animals, but we’re like super-primates," Ungar explained. "We can eat almost anything we want. That’s thanks to our fairly simple gut, our cultural ability to cook and detoxify foods and to our tools, which enable us to break down material that our teeth can’t handle."

Nutritional quality has long been inadequate in the modern human diet. But by demonstrating that the human body is designed to consume the broadest possible range of foods, "Human Diet" suggests that nutritional variety is also lacking. As the medical field continues to find links between diet and disease, it becomes evident that the survival of our species may once again hinge on our ability to consume the right foods.

For more information on "Human Diet: its Origin and Evolution," visit the Bergin & Garvey Web site at http://www.greenwood.com/books/BookDetail.asp?dept_id=1&sku=H736.

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