The Metabolic Syndrome
Obesity increases the likelihood of metabolic complications such as type 2 diabetes, atherogenic dyslipidemias and cardiovascular diseases (see Chapters 76 and 84). On the basis of these associations, the body mass index (BMI) is commonly used to define obesity following a universally accepted definition. Although the BMI has limitations, studies have shown increased incidence of chronic diseases as a function of progressively increasing BMI. Despite this epidemiological evidence, physicians are confronted in their daily practice with the remarkable heterogeneity of their obese patients. Some patients show a severe deterioration in their risk factor profile, whereas others, who are equally obese, do not have the expected complications. Therefore, obesity is a heterogeneous condition, and physicians must go beyond body weight in order to identify and treat high-risk patients.
In this regard, it is important to emphasize the remarkable early clinical observations of Professor Jean Vague from the University of Marseille, who was the first, after World War II, to suggest that the complications of obesity are more closely related to the regional distribution of body fat then to excess fatness per se. In a remarkable short paper published in 1947, Vague suggested that upper body obesity, a condition which he referred to as android obesity, was the dangerous form of obesity found in patients with hypertension, diabetes, or cardiovascular disease, and that the typical female fat distribution, gynoid obesity, was seldom associated with major complications. It took more than 35 years for Vague’s work to receive support from prospective observational studies. In those studies, the proportion of abdominal fat was crudely assessed by the ratio of waistto-hip circumferences, based on the assumption that a higher ratio would reflect greater accumulation of abdominal fat. This ratio has been shown to be a powerful predictor of the incidence of diabetes and cardiovascular disease in prospective studies (see Chapter 68).