Is all fat the same? The role of fat in the pathogenesis of the metabolic syndrome and type 2 diabetes mellitus

The problem of obesity has reached epidemic proportions. Sixty-five percent of US adults are said to be overweight (body mass index, >25 kg/m2).1 Globally, the overweight population is estimated to be 1 billion people.2 This epidemic has led to a resurgence of interest in adipose tissue metabolism, physiology, and pathophysiology. The adipocyte is no longer understood merely as a repository of fat but rather is a dynamic, metabolically active factory that produces metabolic substrates, hormones, cytokines, and adipokines that exert their actions locally, systemically, and even centrally at the hypothalamus to regulate overall energy homeostasis. Increasingly, we understand that obesity is not only a problem of too much fat, per se, but also a much more far-reaching dysregulation of metabolism that affects adipose tissue and other organs, such as the liver, muscle, and pancreas.