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Phase angle as a potential marker of early nutritional and metabolic changes following metabolic bariatric surgery: a
Elif Mizrak1, Halime Pulat Demir2
1Department of Nutrition and Dietetics, College of Health Sciences, Istanbul Medipol University, Istanbul, Türkiye.
Background:
The phase angle (PhA) is associated with nutritional status and serves as a marker of cellular and overall health. The aim of this study is to evaluate changes in PhA during the early postoperative period (6 months) in patients undergoing metabolic bariatric surgery (MBS), and to identify potential factors correlated with these changes.
Methods:
This retrospective study included 120 patients who underwent MBS (Sleeve Gastrectomy, n = 6; Transit Bipartition, n = 114). Biochemical parameters and anthropometric measurements were collected at four time points: preoperatively and at the 1st, 3rd, and 6th postoperative month follow-up visits.
Results:
PhA values at 1-, 3-, and 6-months postoperatively were significantly lower than preoperative values (p < 0.05). PhA was inversely correlated with body mass index (BMI), fat mass, and fat percentage, and positively correlated with muscle mass, fat-free mass (FFM), and total body water (TBW) (p < 0.001). Among these, fat mass showed the strongest negative correlation, while TBW exhibited the strongest positive correlation across all time periods. A significant negative correlation was observed between the amount of change in PhA at 6 months and age (r = -0.283, p = 0.002), while height was positively correlated with the change in PhA at 6 months (r = 0.261, p = 0.004). Ferritin (r = -0.358, p < 0.001) and vitamin D levels (r = -0.234, p = 0.010) were both negatively correlated with the amount of change in PhA at 6 months. In multivariate linear regression analysis adjusting for age, sex, and BMI, vitamin D, and excess weight loss (EWL) remained independently associated with the 6-month change in PhA, while Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) showed a borderline significant association (p = 0.046).
Conclusion:
This study suggests that PhA significantly decreases during the early postoperative period following MBS and is associated with several body composition and metabolic parameters, with vitamin D and EWL emerging as independent predictors of this decline and a borderline association observed for HOMA-IR. These findings suggest that PhA may serve as a potential adjunctive marker reflecting early nutritional and metabolic adaptations in this patient population.
