Bioelectrical Impedance Analysis (BIA) is a method used to estimate body composition, particularly the amount of fat mass and lean body mass. It works by sending a low-level electrical current through the body and measuring the resistance (impedance) encountered. Different tissues, such as muscle and fat, conduct electricity differently, allowing for calculations of body composition based on the resistance values. BIA is commonly used in health and fitness settings due to its simplicity and speed. It can be performed using handheld devices or scales equipped with electrodes. While BIA provides useful estimates, factors like hydration levels and recent physical activity can affect accuracy, so results should be interpreted with caution.