Insulin resistance refers to an aberrant physiological response to insulin in its target tissues. Several signal transduction mechanisms sensing intracellular stress are activated in situations where energy supply exceeds the cells' energy requirements. This stress interferes with insulin-induced intracellular signal transduction and leads to an inflammatory state. The activation of inflammatory responses in peripheral tissues and central nervous system weakens the body's insulin sensitivity, glucose tolerance and predisposes to obesity. Insulin resistance is thus a crucial metabolic disorder in obesity, type 2 diabetes and cardiovascular diseases.