Bioelectrical Impedance Analysis (BIA) estimates body composition, particularly body fat and muscle mass. It is based on the principle that different body tissues conduct electricity differently. During a BIA test, a machine sends tiny electrical currents through the body and measures the resistance to the flow of the currents. Since lean tissue, which is high in water and electrolytes, conducts electricity better than fatty tissue, the resistance measurements can be used to estimate various components of body composition. BIA is favored for its simplicity, speed, and non-invasiveness, making it a popular choice in clinical settings, fitness centers, and personal use. However, its accuracy can be influenced by multiple factors such as hydration levels, food intake, recent exercise, etc., requiring standardized test conditions for reliable results.