Book Review

The Metabolic Syndrome

N Engl J Med 2006; 354:2735-2736June 22, 2006

Article

The Metabolic Syndrome
(Diabetes in Practice.) Edited by Christopher D. Byrne and Sarah H. Wild. 418 pp., illustrated. Chichester, England, John Wiley & Sons, 2005. $115. ISBN: 0-470-02511-5

There is an international dispute among the World Health Organization, the European Group for the Study of Insulin Resistance, and the National Cholesterol Education Program regarding the existence of the metabolic syndrome. This multiauthored book offers an excellent, balanced overview of current knowledge of the syndrome and its importance in current and perhaps future health care. The first chapter addresses the controversial issue of how to classify the metabolic syndrome according to clinical measures. In an assessment of the burden of the metabolic syndrome, the authors estimate that this syndrome affects 10 to 23 percent of the world's population.

It has long been common knowledge that certain types of obesity carry a greater risk of complications than others. This trait has been described in the history of royal families, in which the stout, choleric, pyknic type with central obesity has been shown to be prone to sudden death, stroke, and gout. However, it was not until 1947 that the French scientist Jean Vague discovered that the accumulation of upper-body fat, found mostly in men (android obesity), is associated with an increased frequency of diabetes, hypertension, and cardiovascular disease. In 1988, Gerald Reaven suggested the term “insulin-resistance syndrome” (or syndrome X) to describe a cluster of metabolic abnormalities including hypoalphalipoproteinemia, hypertriglyceridemia, hyperinsulinemia, and increased blood pressure. About five years later, Jean-Pierre Després described an association between visceral obesity and this cluster of metabolic abnormalities and suggested that excess accumulation of visceral adipose tissue is an important component of the condition that is now known as the metabolic syndrome.

The views expressed in this book seem to suggest that visceral obesity is the major component and perhaps even the pathophysiological cornerstone of the metabolic syndrome. However, not all obese persons and not even all persons with abdominal obesity have the metabolic syndrome. This fact has given rise to the suggestion that the presence of the metabolic syndrome may be useful for identifying people with the more serious form of obesity that poses a high risk of cardiovascular disease and type 2 diabetes mellitus. The prevalence of obesity of 20 to 30 percent among the adult population in the United States and Europe certainly points to a need to identify patients for whom treatment is urgently required as compared with patients at low risk. This need, coupled with the fact that pharmaceutical companies are now seeking approval for drugs specifically targeting treatment of the metabolic syndrome, makes the condition a hot topic among scientific, political, and economic groups. This interest was emphasized in a recent discussion paper by the American Diabetes Association and the European Association for the Study of Diabetes in which several interesting questions were raised. First, is the metabolic syndrome indeed a syndrome, particularly given that the precise cause is unknown? Second, does its definition serve a useful purpose? Third, does the use of this term label (and medicalize) people unnecessarily?

This book, which devotes special attention to the environmental and genetic determinants of the metabolic syndrome, includes a chapter on the importance of differences among ethnic groups in the prevalence of the condition. The chapters describing the interplay between inflammation and nonalcoholic steatohepatitis in the pathogenesis of the metabolic syndrome and how adipocytokines may be involved in mediation are exciting. In contrast, the chapter on growth hormone, exercise, and energy expenditure is rather disappointing, because it does not address these topics thoroughly and fails to provide information on how the secretion of growth hormone and energy expenditure are influenced by the presence of the metabolic syndrome.

The Metabolic Syndrome is an excellent collection of updated reviews, and it provides a valuable background for understanding many aspects of this fascinating cluster of risk factors. However, the book does not address the big question — that is, whether a diagnosis of the metabolic syndrome offers a better prediction of cardiovascular risk than do the risk charts that are based on the individual components of the syndrome. This mystery remains to be solved.

Arne Astrup, M.D.
Royal Veterinary and Agricultural University, DK-1958 Copenhagen, Denmark
ast@kvl.dk