Adipose tissue is no longer considered to be an inert tissue that stores fat. This tissue is capable of expanding to accommodate increased lipids through hypertrophy of existing adipocytes and by initiating differentiation of pre-adipocytes. Adipose tissue metabolism exerts an impact on whole-body metabolism. As an endocrine organ, adipose tissue is responsible for the synthesis and secretion of several hormones. These are active in a range of processes, such as control of nutritional intake (leptin, angiotensin), control of sensitivity to insulin and inflammatory process mediators (tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), resistin, visfatin, adiponectin, among others) and pathways (plasminogen activator inhibitor 1 (PAI-1) and acylation stimulating protein (ASP) for example). This paper reviews some of the biochemical and metabolic aspects of adipose tissue and its relationship to inflammatory disease and insulin resistance. Adipose tissue is a metabolically dynamic organ that is the primary site of storage for excess energy but it serves as an endocrine organ capable of synthesizing a number of biologically active compounds that regulate metabolic homeostasis. This dynamic tissue is composed not only of adipocytes, but also of other cell types called the stroma-vascular fraction, comprising blood cells, endothelial cells, pericytes and adipose precursor cells among others. It is now generally recognized that adipose tissue is an important organ of a complex network that participates in the regulation of a variety of quite diverse biological functions. Lipogenesis is a process that occurs preferentially in adipose tissue, but it also happens in liver, and it is the synthesis of fatty acids, which are used as energy reserves. This process is responsive to changes in the diet. Lipolysis occurs in adipose tissue and is the breakdown of fat, in other words, from energy reserves (triacylglycerides) for energy production by which triacylglycerol molecules are hydrolyzed to free fatty acids and glycerol. During times of metabolic stress, the adipocyte's triacylglycrol droplet is degraded to provide free fatty acids to be used as an energy source by other tissues. Adipose tissue secretes a number of bioactive substances, such as adipocytokines among others. Unbalanced production of pro- and anti-inflammatory adipocytokines in obese adipose tissue may contribute to many aspects of the metabolic syndrome (MetS). Oversecretion of potentially harmful adipocytokines, such as PAI-1, tumor necrosis factor-α (TNF-α) or visfatin, and hyposecretion of potentially beneficial adipocytokines, such as adiponectin, might be major mechanisms involved in lifestyle-related diseases, including diabetes mellitus, hyperlipidemia, hypertension andAdipose tissue is no longer considered to be an inert tissue that stores fat. This tissue is capable of expanding to accommodate increased lipids through hypertrophy of existing adipocytes and by initiating differentiation of pre-adipocytes. Adipose tissue metabolism exerts an impact on whole-body metabolism. As an endocrine organ, adipose tissue is responsible for the synthesis and secretion of several hormones. These are active in a range of processes, such as control of nutritional intake (leptin, angiotensin), control of sensitivity to insulin and inflammatory process mediators (tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), resistin, visfatin, adiponectin, among others) and pathways (plasminogen activator inhibitor 1 (PAI-1) and acylation stimulating protein (ASP) for example). This paper reviews some of the biochemical and metabolic aspects of adipose tissue and its relationship to inflammatory disease and insulin resistance. Adipose tissue is a metabolically dynamic organ that is the primary site of storage for excess energy but it serves as an endocrine organ capable of synthesizing a number of biologically active compounds that regulate metabolic homeostasis. This dynamic tissue is composed not only of adipocytes, but also of other cell types called the stroma-vascular fraction, comprising blood cells, endothelial cells, pericytes and adipose precursor cells among others. It is now generally recognized that adipose tissue is an important organ of a complex network that participates in the regulation of a variety of quite diverse biological functions. Lipogenesis is a process that occurs preferentially in adipose tissue, but it also happens in liver, and it is the synthesis of fatty acids, which are used as energy reserves. This process is responsive to changes in the diet. Lipolysis occurs in adipose tissue and is the breakdown of fat, in other words, from energy reserves (triacylglycerides) for energy production by which triacylglycerol molecules are hydrolyzed to free fatty acids and glycerol. During times of metabolic stress, the adipocyte's triacylglycrol droplet is degraded to provide free fatty acids to be used as an energy source by other tissues. Adipose tissue secretes a number of bioactive substances, such as adipocytokines among others. Unbalanced production of pro- and anti-inflammatory adipocytokines in obese adipose tissue may contribute to many aspects of the metabolic syndrome (MetS). Oversecretion of potentially harmful adipocytokines, such as PAI-1, tumor necrosis factor-α (TNF-α) or visfatin, and hyposecretion of potentially beneficial adipocytokines, such as adiponectin, might be major mechanisms involved in lifestyle-related diseases, including diabetes mellitus, hyperlipidemia, hypertension and