## 1 Introduction  
Insulin resistance (IR) is a metabolic condition considered the main etiological factor in the development of Type 2 diabetes [1]. One of its characteristics is that, although it is not deadly, it is associated with several detrimental cardiometabolic risk factors, such as hypertension, hepatic steatosis, dyslipidemia, glucose intolerance, and hyperinsulinemia [1, 2]. In turn, IR is commonly associated with excess body fat (overweight/obesity) and sarcopenia (i.e., muscle mass loss and strength) [3, 4]. This loss of functionality and body composition characteristics is aggravated because, in this condition, individuals have an increased insulin resistance index (HOMA-IR) and, therefore, a lower insulin sensitivity, increasing the risk of IR development [4, 5]. Furthermore, IR is related to reduced cardiorespiratory fitness (VO\({}_{2}\)max), as it is inversely correlated with HOMA-IR and metabolic inflexibility to oxidize fat (Maximal fat oxidation or MFO) [6, 7, 8, 9, 10].  
In this context, the assessment of body composition appears to be important for the prevention or progression of IR [11; 12]. Specifically, excess body fat plays a detrimental role in glucose metabolism [13], whereas greater fat-free mass or lean tissue (FFM) is attributed to a protective role and healthy metabolic profile due to a metabolically active tissue and allows for the uptake of 80% of insulin-stimulated glucose in the body [14; 15; 16]. These components can be determined by dual-energy X-ray absorptiometry (DXA) or bioelectrical multifrequency impedance analysis (BIA), a low-cost alternative technique that allows the estimation of potential health risks [17; 18].  
Accordingly, the relationship between body composition with VO\({}_{2}\)max, HOMA-IR, and MFO remains controversial. [PERSON] and [PERSON] [19] showed a significant inverse correlation between body fat percentage and VO\({}_{2}\)max in healthy young adults (men \(n\) = 30; women \(n\) = 24; age range = 18-25 years) and a positive correlation between FFM with VO\({}_{2}\)max [19]. However, according to the authors' knowledge, there are limited studies on the contribution of body composition to MFO in IR individuals. [20; 21]. In a recently published systematic review, [PERSON] et al. [21] concluded that, in most articles, there was no influence of overweight/obesity on MFO during exercise, although there were conflicting results (8 of 24 articles) [21]. In turn, they mentioned that factors other than body fat (e.g., muscle mitochondrial sparsity) may influence MFO during exercise [21]. Other correlational studies between body composition with VO\({}_{2}\)max and MFO indicate contradictory results. [20; 22]. For example, [PERSON] et al. [20], in young (_n_ = 14) healthy and active (21-31 years) women (_n_ = 14), found no significant correlations between FM and FFM with MFO or VO\({}_{2}\)max [20]. Meanwhile, [PERSON] et al. [22] reported no substantial relationship between fat mass percentage (FM%) and MFO in normal weight (_n_ = 12; 17.2 \(\pm\) 5.7 FM%) and overweight (_n_ = 12; 30.0 \(\pm\) 5.3 FM%) recreationally trained men with equivalent cardiorespiratory fitness (VO\({}_{2}\)max 39.0 \(\pm\) 5.5 vs. 41.4 \(\pm\) 7.6 mL.kg\(\cdot\)min\({}^{-1}\)).  
Consequently, more research is needed to corroborate the contribution of body composition on cardiorespiratory fitness and metabolic markers (i.e., MFO; HOMA-IR; insulin) related to the development or prevention of IR. Therefore, this study aimed to determine the body composition influence on cardiorespiratory fitness and metabolic markers in physically inactive individuals with IR.