Electrical bioimpedance in the assessment of body composition: a review of biophysical principles, different types, methodological aspects, validity and applicability of their measurements

The assessment of body composition is an important aspect in determining physical conditions in different health-related processes. It assists both in research and in weight loss situations or in the prevention/treatment of chronic diseases such as diabetes, arterial hypertension, dyslipidemia and cardiovascular diseases. Bioelectrical impedance (BIA), as it is an easy-to-carry, non-invasive and quick-to-use device, has been gaining great prominence in the market. Thus, the objective of this work is to review the use of BIA in the assessment of body composition, focusing on discussing the different types of BIA, presenting its centrais idea, its main methodological aspects and the validity of the measures it offers. In general, it is possible to observe that there is a variety of BIA devices that are categorized by the number of electrodes used, by the region submitted to the evaluation or by the frequency used. In both devices, operation is based on the opposition between resistance and reactance. Additionally, the accuracy of the measurements of this method presents satisfactory results, when some standardized procedures and protocols are observed. However, situations of abnormal hydration, severe malnutrition, obesity, neuromuscular or extensive dermatological diseases require more attention from the evaluator when interpreting the results.