###### Abstract
WC, an easy and low-cost parameter, is considered to be a more sensitive and accurate method than the BMI or waist-to-hip ratio for assessing central obesity [12]. Last but not least, WHtR has an even stronger ability to predict the risk of developing cardiovascular disease, metabolic syndrome, and type 2 diabetes [13]. A WHtR above 0.5 is generally considered a diagnostic criterion for central obesity [10]. Furthermore, the \"obesity paradox\", represented by an inconsistent or inverse association between obesity indicators and cardiovascular mortality in various populations, has led to the identification of several novel adiposity indexes, such as the A Body Shape Index (ABSI) and Weight-Adjusted Waist Index (WWI). The ABSI has been found to be more closely associated with cardiovascular risk [14]. The WWI, which adjusts the WC relative to weight, offers several advantages over the traditional markers of obesity. Several studies have identified it as an important predictor of diabetes, cardiovascular disease, and non-accidental mortality risk [14; 15; 16]. Further research aims to determine new optimal cut-off values for the existing anthropometric measures of obesity [17; 18]. There are several methods for objectively evaluating the amount of body fat: density measurement methods--air-displacement plethysmography (AP) and underwater weighing--bioelectrical impedance analysis (BIA), dual X-ray absorptiometry (DEXA), and computer imaging methods, including magnetic resonance imaging (MRI) and computed tomography (CT). Each of these methods has advantages and disadvantages. AP is a non-invasive relatively accurate method, with a %BF error margin of 1% to 2% and high repeatability [19]. It uses a two-air-filled-chamber closed system in which repeated volume and pressure variations are produced. Under the assumption of an adiabatic process, body volume and, consequently, body density are computed. Although precise, AP has the disadvantage of expensive equipment, with higher complexity and measurement time. BIA is a safe portable method, with affordable equipment, which has become popular in recent decades. It measures body impedance and reactance. %BF is calculated using predictive equations that vary according to age, sex, ethnic group, or various clinical conditions [19; 20]. BIA's accuracy is influenced by the type of equipment (and associated algorithms) [21], as well as by environmental factors and subject characteristics. Environmental factors include humidity and temperature, while subject characteristics include body geometry that may vary between ethnic groups. Specifically, fat distribution patterns or variability in limb length can differ between ethnic groups and so may influence BIA's accuracy [22; 23]. There are several studies assessing BIA's reliability against AP in healthy adult populations [24; 25; 26; 27; 28]. There are also studies comparing BIA with other techniques to determine body fat in overweight and obese subjects classified according to the BMI criteria [29; 30; 31; 32; 33]. Taking a closer look at BIA, as background information, it is known that bioelectrical impedance measurements depend on the assumption that the impedance of a conductor is determined by its length and configuration, as well as by its cross-sectional area. In this model, the human body is considered to be composed of cylinders with a uniform electric conductivity, corresponding to the four limbs and the trunk. The subject height is used to represent the conductive length. Abdominal obesity is defined by a larger waist circumference, hence a wider cross-sectional area of the trunk. Although it has been observed that the introduction of the waist circumference in the equations used to compute %BF improves the predictive value in the elderly [19], it has not been tested whether the higher values in subjects with abdominal obesity impact BIA's accuracy. The present study aimed to establish whether the body geometry changes associated with abdominal obesity influence BIA's agreement with AP in determining %BF.