Phase angle: Differences between disease-related malnutrition, obesity and healthy people.

Introduction: Bioelectrical Impedance Analysis (BIA) is a tool used in clinical nutrition and pure electrical data such as phase angle (PA) has shown prognostic value. It relates resistance and reactance indicating cellular health.

Objective: To determine differences in PA between patients with obesity and disease-related malnutrition (DRM) compared to the healthy population, and to establish associations between PA and other body composition (BC) parameters.

Materials and methods: Retrospective observational study with 1079 patients from the Obesity and Nutrition Department of the Complejo Asistencial Universitario de León between April/2014 and August/2022 as well as 86 healthy controls. Demographic and anthropometric variables were collected and BC was performed with BIA Tanita MC780®. Diagnosis of malnutrition according to GLIM criteria and obesity with body mass index (BMI).

Results: PA50KHz in obesity group is 5.98º, DRM 4.79º and control group 6.08º. Statistically significant differences in PA between DRM and control groups, as well as DRM and obesity (p < 0.001). Weak positive correlation in total population (r = 0.452, p < 0.001) as well as control group (r = 0.463, p < 0.001) between BMI and PA. Weak negative correlation in the total population (r = -0.408, p < 0.001), DRM (r = -0.268, p < 0.001) and obesity (r = -0.342, p < 0.001) between age and PA.

Conclusions: In this study, significantly lower PA was observed in the DRM group than in the control and obesity groups. No statistically significant differences between PA in the obesity and control groups and no correlation between BMI and PA in the obesity group. More studies are needed to standardize cut-off points in different contexts and populations.