[Concept and classification of obesity].

Obesity is recognized as a disease when it is associated with current or future health problems. The association of obesity with hypertension, glucose intolerance, and lipid metabolism disorder is diagnosed as metabolic syndrome since it tends to cause arteriosclerotic diseases. Obesity is important since it is pandemic throughout the earth. In this review we explain the concept and classification of obesity. We discuss the disease basis of obesity and metabolic syndrome, especially from the standpoint of adipotoxicity.