Obesity, lipid disorders, type 2 diabetes, high blood pressure and coronary heart disease are frequently encountered in wealthy populations. All these disorders frequently occur as clusters, constituting the metabolic syndrome. It is currently admitted that insulin resistance plays a central role in the pathogenesis of this syndrome. Stress responses include activation of the sympathetic nervous system and stimulation of epinephrine and cortisol release. These hormones may over the long term reduce insulin sensitivity. Cortisol may also favour the development of central obesity. In healthy individuals, mental stress increases heart rate, but simultaneously decreases vascular resistance in skeletal muscle. This results in a moderate increase in blood pressure, and an acute increase in insulin-mediated glucose disposal. In obese patients, mental stress elicits responses which differ widely from those of healthy individuals. While mental stress enhances catecholamine-mediated energy expenditure in obese patients to the same extent as in lean subjects, it fails to decrease systemic vascular resistance due to endothelial dysfunction. This leads to enhanced blood pressure responses and the absence of stimulation of glucose disposal in obese subjects during mental stress. It can be hypothesized that repeated professional or social stress may activate the sympathoadrenal system, resulting in high cortisol levels, stimulation of the sympathetic nervous system, and epinephrine secretion. All these factors may eventually lead to the development of central obesity and insulin resistance. Furthermore, the blood pressure responses to mental stress may be enhanced in insulin-resistant individuals, favouring the development of vascular complications.