Background: Obesity is a complex metabolic disorder associated with an increased risk of cardiovascular disease, type 2 diabetes, and other metabolic complications. Traditional indices, such as body mass index (BMI), do not allow for an accurate assessment of body composition or the distinction between fat and fat-free mass. Bioelectrical impedance analysis (BIA) is a rapid, non-invasive tool for assessing body composition in clinical settings. Objective: The aim of this study was to evaluate the clinical utility of BIA in the diagnosis and monitoring of obesity, including body composition assessment, identification of obesity phenotypes, diagnosis of sarcopenic obesity, stratification of cardiometabolic risk, and monitoring of the effects of dietary, pharmacological, and surgical treatment. Materials and Methods: A narrative review was conducted of 47 scientific publications published between 1990 and 2026, most of which were from the last decade. The review included clinical trials, systematic reviews, cohort studies, and mechanistic studies on the application of BIA in obesity. The analysis focused on body composition parameters (FM, FFM, TBW, FMI, FFMI, PhA), the detection of obesity phenotypes, cardiometabolic risk, and treatment monitoring. Results: BIA allows for the assessment of fat mass, fat-free mass, water content, and derived indices (FMI, FFMI, PhA). These parameters enable a more accurate characterization of obesity phenotypes than BMI. Data from literature reviews show that BIA supports the identification of individuals with elevated cardiometabolic risk, detects sarcopenic obesity, and monitors changes in body composition during therapy. Conclusions: BIA is a practical, non-invasive tool that aids in the diagnosis and monitoring of obesity treatment. Despite certain methodological limitations, its reproducibility, accessibility, and ability to provide a multidimensional assessment of body composition make it a valuable complement to other clinical methods.
Szmuc et al. (Mon,) studied this question.