[Obesity and the immune system].

With an increased prevalence of obesity in developed countries, associated chronic diseases rise in a parallel way. Morbidity secondary to overweight and obesity include type 2 diabetes, dislipemia, hypertension, heart disease, cerebrovascular disease, cholelithiasis, osteoarthritis, heart insufficiency, sleep apnoea, menstrual changes, sterility and psychological alterations. There is also a greater susceptibility to suffer some types of cancer, infections, greater risk of bacteremia and a prolonged time of wound healing after surgical operations. All these factors indicate that obesity exerts negative effects upon the immune system. Immune changes found in obesity and their possible interrelations are described in this article. Changes produced during obesity affect both humoral and cellular immunity. It is known that adipose tissue, together with its role as energy reserve in form of triglycerides, has important endocrine functions, producing several hormones and other signal molecules. Immune response can be deeply affected by obesity, playing leptin an important role. Properties of leptin, alterations of leptin levels in different situations and its changes with different medical and surgical therapies for obesity are described in this article.