Adiposity

Adiposity refers to the amount or distribution of adipose tissue in the body. It is commonly assessed as body fat percentage or through the proportion of fat mass to lean mass, but with attention to the regional distribution of fat, which has distinct health implications. Adipose tissue exists in several forms, most notably white adipose tissue, which stores energy; brown adipose tissue, which generates heat; and beige adipose tissue, which can acquire brown-like properties under certain conditions. In terms of distribution, subcutaneous adipose tissue lies beneath the skin, whereas visceral adipose tissue surrounds internal organs. Visceral fat accumulation is more strongly associated with metabolic and cardiovascular risk than subcutaneous fat.

Measurement methods include BMI as a rough proxy, waist circumference and waist-to-hip ratio for central adiposity, and more direct assessments such as dual-energy X-ray absorptiometry (DEXA) or imaging techniques that quantify visceral fat.

Adipose tissue is an active endocrine organ producing adipokines such as leptin, which regulates appetite and energy expenditure; adiponectin, which improves insulin sensitivity; and inflammatory cytokines. These signals influence metabolism, inflammation, and glucose homeostasis. Excess adiposity, particularly visceral, contributes to insulin resistance, metabolic syndrome, type 2 diabetes, hypertension, dyslipidemia, and nonalcoholic fatty liver disease. Conversely, severe loss of adipose tissue in lipodystrophy can cause metabolic complications due to ectopic fat deposition.

Causes are multifactorial, including genetics, prenatal and early-life factors, diet, physical activity, and the built environment. Management focuses on reducing risk through sustained weight loss, improved lifestyle, and, in some cases, pharmacotherapy or bariatric surgery. Understanding adiposity requires considering both total fat and its distribution, as well as the functional properties of adipose tissue in health and disease.