Sarcopenia, clinically characterized by progressive deterioration of skeletal muscle mass and functional capacity (1), has emerged as a critical global health challenge with substantial socioeconomic implications (2). From the age of 35, the human body experiences a gradual decline in muscle mass, with an approximate rate of 1-2% per year. After the age of 65, this rate of loss accelerates significantly, reaching up to 3% per year (3). This suggests that the risk of declining muscle quality and function commences in early adulthood, thereby further exacerbating the risk of muscle dysfunction in later life. While geriatric sarcopenia has received considerable scientific attention, muscle mass loss in younger populations remains underrecognized in clinical practice. Modern lifestyles (such as sedentary lifestyles and high-fat diets) have precipitated an epidemic surge in adiposity among younger cohorts (4, 5), and the coexistence of obesity and low muscle mass may synergistically exacerbate metabolic homeostasis disruption (6). Mounting evidence underscores the interplay between sarcopenic progression and metabolic dysregulation (7). Ongoing intensive research into sarcopenia has revealed insulin resistance (IR) as a significant factor in its progression, and simultaneously obesity can exacerbate IR and muscle atrophy (8). Consequently, the investigation of more accurate obesity-related markers of IR is essential for the timely identification of IR and the prevention of sarcopenia.

The TyG index is widely acknowledged as an efficacious and cost-effective marker for assessing IR, calculated from triglycerides and fasting glucose levels (9, 10). Recent studies have indicated that obesity indices associated with the triglyceride glucose(TyG) index offer a more precise evaluation of IR, such as the TyG-waist-to-height ratio (TyG-WHtR) (11, 12), as well as accurately reflect the risk of periodontitis, cardiovascular, diabetes, and other diseases (13–15). Prior research has established a connection between the TyG index and reduced muscle mass among the Korean population, as well as a positive correlation between the TyG index and sarcopenia among the US population (16, 17). Nevertheless, there is a paucity of studies investigating the correlation between different TyG index-related obesity indicators and sarcopenia.

Accordingly, this present study represents the first investigation into the correlation between multiple TyG index-related obesity indicators and sarcopenia, utilizing data obtained from The National Health and Nutrition Examination Survey (NHANES). Furthermore, the comparative analysis of TyG index-related obesity indicators with conventional TyG indices is undertaken with a view to identifying the optimal diagnostic efficacy, and thus providing a novel rationale to inform the prevention and evaluation of sarcopenia.

This cross-sectional study included 4,804 participants, with 428 diagnosed with sarcopenia. Our findings revealed a notable and positive correlation among TyG-WWI, TyG-BMI, TyG-WHtR and TyG-WC with a prevalence of sarcopenia. The aforementioned relationship remained consistent when the indices were divided into quartiles. Subgroup analysis revealed a more pronounced correlation between four indices and sarcopenia in the gender-stratified subgroup with a BMI of 30 or above. Additional ROC analysis demonstrated that the diagnostic effectiveness of four TyG-related obesity indicators was more pronounced than that of TyG. Notably, TyG-WWI demonstrated the best diagnostic efficacy in identifying individuals with sarcopenia.

Sarcopenia risk begins to escalate as early as young adulthood, with a global prevalence approximating 10% in individuals (21). Longitudinal analysis of the NHANES 1999-2006 cohort further corroborates this trend, demonstrating a significant rise in sarcopenia prevalence among adults aged 18-39 years over the study period (22). As the physical activity of young people gradually declines, there is a concomitant decrease in muscle mass and strength (23, 24). The loss of muscle mass in young people has been demonstrated to have a detrimental effect on the prevalence of sarcopenia (25). Despite the relatively low prevalence of sarcopenia in young adults, the prolonged duration of muscle loss in youth has the potential to result in elevated morbidity over time (26). Consequently, the identification and prevention of sarcopenia in young people has the potential to reduce its prevalence. Early identification and treatment of sarcopenia in young people are necessary to limit the progression of the disease and related complications (27). The present study demonstrated that TyG-WWI and TyG-BMI exhibited considerable predictive and early recognition value for sarcopenia in young and middle-aged individuals. These indicators may also contribute to delaying the progression of sarcopenia in the elderly population. Our findings demonstrate that the TyG-WWI and TyG-BMI exhibit robust predictive and discriminative capacities for identifying sarcopenia in young and middle-aged populations. These indices may further contribute to delaying the progression of geriatric sarcopenia. Notably, TyG-related obesity indicators are characterized by both low cost and ease of clinical access. This renders them particularly suitable for early screening of sarcopenia risk in middle-aged and elderly populations. The subsequent effect of this is to guide early treatment and intervention, such as resistance training (28, 29). In light of the escalating prevalence of obesity and the growing incidence of metabolic disorders among the younger population (30, 31), the prevention and monitoring of sarcopenia and its associated complications in middle-aged and young adults has become a pressing concern. At present, there has been a paucity of research conducted on this population. The findings of this study provide a basis for further research in this area, suggesting that individuals of both the young and middle-aged should observe and monitor the dynamic changes in the TyG-WWI and TyG-BMI indexes.

A number of the most recent studies corroborate our assertion. Although TyG-related obesity indices have been less well studied in relation to sarcopenia, TyG indices have been observed to be associated with low muscle mass as well as sarcopenia in various populations. Two population-based studies in Korea have established a connection between this indicator and the likelihood of low muscle mass (16, 32). The findings of Yang et al. indicated a favorable relationship between the TyG index and sarcopenia in US adults (17). Pan et al. have shown a nonlinear positive connection between TyG-BMI and sarcopenia (21). This finding is aligned with the results of our study. However, the previous research was limited in that it examined the TyG-BMI as a standalone index and did not compare it with other indications, which include the TyG indicator and those related to obesity. Our study proceeded to investigate whether the four distinct TyG-related indices of obesity exhibited a greater predictive capacity for sarcopenia compared to a single TyG index. It is noteworthy that the TyG-WWI index exhibited optimal diagnostic validity for sarcopenia, which may potentially serve as a predictor of sarcopenia.

Our subgroup analysis revealed a significant influence of gender on the relationship between TyG-WWI, TyG-WHtR, TyG-BMI, and sarcopenia. Previous studies have come to similar conclusions as ours (21). The results of some population-based surveys suggest that gender and risk with regard to sarcopenia are not entirely consistent (33, 34). Estrogen may be a factor influencing the gender differences observed in this association between males and females (35). A deficiency of estrogen has been linked to the atrophy of skeletal muscle and the accumulation of fat tissue, as well as the suppression of fatty acid beta-oxidation in both skeletal muscle and fat tissue. The development of sarcopenia is believed to be influenced by this factor (36–38). Chen et al. show that changes in estrogen levels may attenuate the correlation between the TyG index and sarcopenia in women (39). Subjects with a BMI of 30 or greater showed significant positive associations with sarcopenia concerning four indices. The relationship between sarcopenia and IR is affected by obesity, particularly in the context of sarcopenic obesity, where IR status is negatively correlated with skeletal muscle mass (40). An investigation conducted on elderly Chinese patients with diabetes revealed a heightened sarcopenia risk connected to elevated body fat levels., which supports the aforementioned findings (41). Therefore, obesity may influence the development of sarcopenia and the correlation between sarcopenia and TyG-related indices of obesity.

IR is a significant contributor to the initiation and advancement of sarcopenia. Furthermore, the extent of IR is influenced by the magnitude of sarcopenia severity, whereby the presence of obesity plays a pivotal role in this interconnection (8, 42). IR stimulates the release of sarcopenia, which in turn reduces protein synthesis in skeletal muscle and accelerates skeletal muscle protein catabolism (8). Simultaneously, sarcopenia can facilitate IR through lipotoxicity and inflammation resulting from lipid infiltration and aberrant accumulation, as well as by reducing the percentage of type I fibers in skeletal muscle (43). The results of an NHANES III-based study demonstrated that sarcopenia intensified obesity-related insulin resistance (44). This indicates the potential for a complex interrelationship between IR, obesity, and sarcopenia. At present, there is a greater understanding of the intricate relationships between IR, obesity, and sarcopenia. Prior research has indicated that individuals with sarcopenia may be predisposed to an increased risk of obesity as a consequence of their diminished activity levels (45). Obesity is often associated with a degree of inflammation. Fat accumulation often triggers an inflammatory response that leads to fat infiltration of skeletal muscle and the gradual formation of intermuscular adipose tissue (IMAT) and intracellular myocyte lipid droplets (IMCL), which are key contributors to the muscle resistance to IR (46, 47). Abnormal lipid accumulation also induces mitochondrial dysfunction, exacerbates local oxidative stress and inflammation, and contributes to the inhibition of the insulin-PI3K-mTOR pathway by protein kinase C (PKC) and p38-MAPK (48). Inflammatory cytokines have been shown to induce muscle atrophy (49), and their elevated levels impede the synthesis of insulin and insulin growth factor 1(IGF-1), further exacerbating the development of IR (50).

The present study has the following advantages: This is the inaugural study to investigate the connection among distinct TyG-related obesity indicators with sarcopenia in a US population using data from the NHANES database. Secondly, the study adjusted for potential confounding variables wherever possible and performed subgroup analysis and interacting tests to examine the impact of various elements on the relationship among the TyG-related obesity indicators with sarcopenia. Ultimately, we used ROC curves to judge the diagnostic effectiveness of individual TyG-related obesity indices and identify superior indicators compared to the TyG index, thereby establishing a novel reference for evaluating and predicting sarcopenia. It should be noted that the current study has limitations. First, the cross-sectional study design hinders the identification of causality connection among the indices with sarcopenia. Second, although this study adjusted for a considerable number of confounding variables, it was nevertheless not possible to rule out the potential impact of undetected confounders on the findings. Finally, due to an absence of data about muscle function (e.g. gait speed) in the NHANES data, the assessment of sarcopenia relied exclusively on DXA-derived body composition measures and more professional and comprehensive diagnostic criteria for sarcopenia could not be applied. Furthermore, due to the limitations of DXA, the study’s participants ranged in age from 20 to 59 years, precluding in-depth investigation of the older population. It is therefore recommended that future research employ more longitudinal studies to explore this issue in greater depth.

The TyG-WWI, TyG-WHtR, TyG-BMI, and TyG-WC demonstrated a nonlinear and significant positive correlation with a prevalence of sarcopenia. Furthermore, these four indices exhibited superior diagnostic accuracy in detecting sarcopenia compared to the TyG index. Notably, we found optimal diagnostic validity of TyG-WWI for sarcopenia. This indicates that the TyG-related obesity indices, specifically the TyG-WWI index, have potential as reliable indicators for assessing and predicting sarcopenia.