The metabolic syndrome (MetS) or the “insulin resistance syndrome” was described by G. M. Reaven in the late 1980s, but scientists had already identified various coexisting components of this syndrome as early as the 1920s (Sarafidis and Nilsson 2006). Today, several definitions of MetS exist, causing confusion as to whether they identify the same individuals or evaluate a surrogate of risk factors (Kassi et al. 2011). According to the International Diabetes Federation (IDF), MetS diagnostic criteria include abdominal obesity and two of the following four factors: raised triglycerides (TG), reduced high-density lipoprotein (HDL) cholesterol, raised blood pressure, and raised fasting plasma glucose (Huang 2009). Recently, other factors also linked to the syndrome have been identified, such as chronic pro-inflammatory and pro-thrombotic states, nonalcoholic fatty liver disease, and sleep apnea (Kassi et al. 2011). Factors leading to the development of MetS are illustrated in Figure 7.1.