Non-Linear Association Between Phase Angle and Body Fat in a Sample of US Adults

Area of Science:

• Bioimpedance analysis
• Human physiology
• Body composition

Background:

• Phase angle (PhA) is a bioimpedance metric linked to cell integrity and body composition.
• The relationship between PhA and body fat remains unclear in scientific literature.

Purpose of the Study:

• To investigate the non-linear association between Phase angle and various measures of body fat in adults.
• To explore potential sex differences in the Phase angle-body fat relationship.

Main Methods:

• Utilized data from 1533 adults in the National Health and Nutrition Examination Survey.
• Employed anthropometry, bioimpedance analysis (BIA), and dual-energy X-ray absorptiometry (DXA) for body composition assessment.
• Applied non-linear cubic spline regression to analyze relationships between PhA and fat mass (FM), BMI, FMI, and FM%.

Main Results:

• A non-linear relationship was observed between PhA and body fat indices (FM, BMI, FMI, FM%).
• Men exhibited inflection points at lower body fat levels compared to women.
• The explained variance for these relationships was consistently below 10%, indicating a weak association.

Conclusions:

• Phase angle demonstrates a weak and non-linear association with body fat.
• Factors other than body fat predominantly influence Phase angle variability.
• Clinical and routine interpretations of PhA should consider its limited relationship with body fat.