ABSTRACT
The human body consists of more than 40 major body components distributed across atomic, molecular, cellular, tissue–organ, and whole-body organizational levels. Evaluation of overweight and obesity includes quantifying these varying components in research, clinical, and field settings. Lipids, specifically triglycerides or “fat,” are associated with adiposity components at all five levels. The largest fat-containing component is the tissue–organ level adipose tissue distributed in the subcutaneous and internal body compartments. Magnetic resonance imaging and computed tomography can quantify total body and regional adipose tissue volumes, brown adipose tissue, and ectopic fat depots. Hydrodensitometry, air-displacement plethysmography, and hydrometry are methods that quantify molecular-level total body fat based on two-component models that divide body mass into fat and fat-free mass. Ultrasound and anthropometric skinfold measurements provide estimates of regional adipose tissue characteristics that can be used with statistical prediction equations to estimate total body adipose tissue or fat mass. Measurements made with bioimpedance analysis, three-dimensional optical imaging, and a conventional tape measure can be used alone or with statistical prediction equations to estimate multiple different adiposity components. This array of classical and new methods provides investigators and practitioners with a range of adiposity measurement options that are applicable in diverse settings.
