What is white fat?

White fat, officially called white adipose tissue (WAT), is the predominant type of fat tissue in adults, appearing yellowish-white and primarily functioning to store energy as triglycerides while also providing insulation, cushioning, and hormone production.

White fat cells (white adipocytes) contain a single large lipid droplet occupying most of the cell volume, pushing the nucleus and cytoplasm to the cell periphery. This structure maximizes fat storage capacity—when calorie intake exceeds expenditure, excess energy is converted to triglycerides and stored in these droplets, creating an energy reserve providing approximately 9 calories per gram. White fat distributes throughout the body in two main patterns: subcutaneous fat (beneath the skin, particularly in hips, thighs, buttocks, and abdomen) and visceral fat (around internal organs in the abdominal cavity). These locations serve different functions—subcutaneous fat provides insulation against heat loss and cushions against impacts, while visceral fat cushions organs but when excessive, increases health risks including diabetes, cardiovascular disease, and metabolic syndrome. Beyond energy storage, white fat actively secretes hormones and signaling molecules. Leptin, produced by white adipocytes, signals energy stores to the brain, regulating appetite and metabolism. Adiponectin enhances insulin sensitivity and has anti-inflammatory properties. White fat also produces other molecules affecting inflammation, blood pressure, and blood clotting. White fat contrasts with brown fat (brown adipose tissue), which contains multiple smaller lipid droplets and numerous mitochondria, specializing in heat generation rather than energy storage. Adults possess much more white than brown fat. Recently discovered "beige" fat represents white fat that can develop brown fat-like characteristics under certain conditions. Understanding white fat helps inform healthy weight management—moderate amounts support normal function, while excessive accumulation (particularly visceral fat) requires intervention through diet, exercise, and sometimes medical treatment to reduce health risks.