## 4 Discussion
[PERSON] et al. [12] found that although the negative correlation of the WWI with muscle mass was weak compared to its positive correlation with fat mass, the WWI is potentially the only indicator that can reflect various changes in body composition. However, we must emphasize the urgency of distinguishing between the quantitative and relative representation of fat-free and muscle mass in particular, because while the quantitative expression of these components showed weak positive correlations with the WWI, their relative expression already showed strong negative correlations. The WWI has been shown to be less sensitive than BMI and is a better predictor of metabolic disease risk than not only BMI but also WC [49; 50]. This index provides a more accurate representation of visceral obesity and has been confirmed as a better predictor of morbidity and mortality from obesity-related diseases. Research suggests that the WWI outperforms BMI, WC and WHtR as a predictor of cardiovascular disease mortality [8; 44; 51; 45]. Studies further indicate a stronger association of the WWI with sarcopenia obesity than other anthropometric indicators, including BMI and WC. With an increasing WWI, fat mass increased and muscle and bone mass decreased [48]. However, our results did not confirm this dominance: the correlation relationships were similarly strong (WWI, BMI, WC vs. FM/FFM r = 0.900, r = 0.925 and r = 0.918, respectively). Other authors found that in older individuals over 65 years of age, the WWI was positively associated with total and abdominal fat but negatively associated with appendicular skeletal muscle mass [12]. Increasing age is also associated with the redistribution of adipose tissue to visceral and ectopic areas, i.e., also to bone and muscle tissue [52; 53]. Muscle mass and strength peak between the ages of 30 and 40 and then decline, leading to sarcopenia [54]. During ageing, fat mass increases and muscle and bone mass decrease, leading to changes in body composition towards an unhealthy state [55; 56]. S sarcopenia is characterized by reduced muscle mass and strength, which is primarily associated with the ageing process [57]. Sarcomenia is accompanied by a gradual increase in adipose tissue mass, especially visceral fat, leading to the development of sarcopenia obesity. Although currently considered a common problem in older people and associated with poor health [58; 59], this condition is gradually shifting to lower age categories. Unlike commonly used anthropometric indices, the WWI reflects various changes in body composition related to age [12; 48]. [PERSON] et al. [60] emphasize, based on their findings, the necessity of correlating anthropometric indicators with biochemical and clinical variables in the risk assessment and diagnosis of various metabolic diseases. Therefore, in our study, we also focused on the associations of the WWI with biochemical parameters. [PERSON] et al. [61] found that the WWI has a greater impact on inflammatory markers than the marker of total obesity (BMI). Our results also partially confirm this, although only in the case of hs-CRP (r = 0.356 for the WWI, r = 0.342 for the BMI). Compared to the BMI, the WWI showed stronger correlations with the biochemical parameters, except for glucose, but the differences were not large. The WWI showed a strong positive correlation with uric acid, which is an indicator of cardiovascular diseases. We found a moderate positive association between the WWI and diastolic blood pressure and TG, and a negative one with HDL-C. These associations are related to adipose tissue dysfunction, which leads to increased production of pro-inflammatory cytokines involved in processes leading to endothelial dysfunction and cardiovascular events, as well as to increased oxidative stress with the production of free radicals with the risk of carcinogenesis. An increased WWI reflects adipose tissue dysfunction, suggesting abnormal lipid levels and lipid metabolism disorders [62; 63; 64; 65].