Phase angle is a parameter derived from bioelectrical impedance analysis (BIA), a non-invasive method used to assess body composition and health. BIA involves passing a low-level electrical current through the body and measuring how it is impeded by the various tissues and fluids. The phase angle is one of the values obtained from this measurement.

The phase angle is the result of the relationship between two components of the electrical current as it passes through the body.

Resistance (R): Resistance is the opposition that electrical flow encounters as it passes through tissues and fluids. It is associated with the body's lean mass, including muscle and other cellular structures. Higher resistance values typically indicate a higher proportion of lean tissue.

Reactance (Xc): Reactance is related to the storage and release of energy in the cells and is influenced by cell membrane integrity and the quality of the cellular mass. It is associated with the body's cell health and vitality.

The phase angle is the arctangent of the ratio of reactance to resistance (arctan[Xc/R]) and is typically measured in degrees. It reflects the cell membrane's capacitance and the integrity of cell membranes, which are important indicators of cell health. A higher phase angle is generally associated with better cellular health and integrity.

Researchers and healthcare professionals use the phase angle as a valuable marker for assessing cellular health and predicting various health outcomes. A low phase angle may be indicative of poor cell health and is associated with conditions such as malnutrition, muscle wasting, and a weakened immune system. However, the interpretation of phase angle values can vary depending on the specific context and population being studied.