Current definitions of obesity rely on the body mass index (BMI) and people are generally classed as obese if they have a BMI over 30. Beside this index, obese people are characterized by an individual excess of body fat that is considered of being unhealthy. Obesity is a major risk factor for a number of clinical manifestations, including diabetes, cardiovascular diseases, as well as certain cancers. The root cause of obesity is energy imbalance regardless the underlying genetic and environmental determinants. Once considered to be a specifi c health problem of industrial nations, obesity is now also markedly increasing in developing countries.

White Adipose Tissue (WAT) & Adipokines

Obesity is primarily characterized by excess of body fat or white adipose tissue (WAT). Within WAT differentiated cells called adipocytes are specialized in storing fat. The increase in WAT/body fat is caused by a combination of differentiation of preadipocytes and size increase of mature adipocytes. Next to pre- and mature adipocytes, WAT also consists of other cell types such as macrophages and fi broblasts. WAT has been long known for its role in mechanical cushioning, heat insulation, and as an energy depot of triglycerides. However, today WAT has been drawn intensive attention in obesity research, because it has been recognized as a source of endocrine and paracrine signaling molecules important in many physiological and metabolic processes. These signaling molecules are diverse in both structure and function, and are called adipokines. The term “adipokines” is not consistently defi ned. In general, it describes cytokines which are mainly produced by adipose tissue, although they don`t derive exclusively from this organ. The rapidly increasing number of adipokines from either source refl ects the importance of WAT as an endocrine and paracrine organ. Insulin resistance and coronary diseases seem to be more closely associated with visceral- rather than subcutaneous fat depots.