Insulin resistance is a central feature of metabolic syndrome, also known as syndrome X. Individuals with metabolic syndrome commonly have elevated total cholesterol, low HDL cholesterol (the “good” cholesterol), high LDL cholesterol (the “bad” cholesterol), and elevated triglycerides. Insulin resistance is also closely linked to obesity, particularly excess abdominal fat, and is often accompanied by high blood pressure.
Another key component of metabolic syndrome is chronic inflammation and impaired endothelial function, referring to dysfunction of the inner lining of blood vessels. Elevated cholesterol—especially high LDL—raises cardiovascular risk, while inflammation promotes plaque formation (atherosclerosis). Healthy endothelial function helps protect against this process.
Research published in Journal of the American Medical Association (2004; Volume 292, Pages 1440–1446) examined whether the Mediterranean diet could improve inflammation and endothelial function in people with metabolic syndrome. This randomized, single-blind trial followed 180 participants (99 men and 81 women) for 2½ years. Participants were assigned either to follow a Mediterranean-style diet or to a control group.
Those following the Mediterranean diet showed significantly lower levels of inflammatory markers, including C-reactive protein (CRP) and interleukins IL-6, IL-7, and IL-18. Measures of endothelial function also improved in the diet group. In addition, insulin resistance improved: at the end of the study, only 40 participants in the Mediterranean diet group still met criteria for metabolic syndrome, compared with 78 participants in the control group.
