Colorectal cancer (CRC), a malignant neoplasm, is witnessing an escalating prevalence on a global scale. Its morbidity and mortality figures stand among the highest in different kinds of cancers. In 2022, there were more than 1.9 million newly reported cases, and the number of fatalities reached 904,000 (1). The prevalence of colorectal cancer is rising in various nations, including China and the United States, with an increasingly younger demographic being impacted (2, 3). In light of this context, it is crucial to aggressively investigate more effective methods for the prevention and screening of CRC to significantly diminish its incidence rate.

The incidence of obesity has witnessed exponential growth on a global scale as a result of lifestyle alterations, impacting over 650 million individuals (4). In particular, it has been established that visceral obesity is a significant risk factor for CRC development (5, 6). However, it has been shown that traditional measures of obesity, like the body mass index (BMI), possess limitations when it comes to evaluating the risk of CRC, as they are unable to accurately reflect the characteristics of fat distribution (7, 8). Furthermore, the precision of BMI in gauging obesity has been cast in doubt on account of its inbuilt limitations (9). A body shape index (ABSI) was developed by Krakauer and his fellow researchers in 2012. With waist circumference (WC) being its basis, it is adjusted corresponding to height and weight. Under certain height and weight circumstances, if the ABSI is raised, it is more prone to suggest a larger portion of visceral (abdominal) fat rather than peripheral tissue (10). The index has demonstrated superior efficacy in predicting the health consequences of obesity, as elevations in the ABSI correlate with substantial increases in mortality, underscoring the insufficiency of standard obesity indicators in assessing health hazards (11). The ABSI effectively addresses some constraints inherent in relying solely on overall or central obesity markers, hence facilitating the investigation of relationships with cancer risk (12). Nonetheless, to date, only a restricted number of research have investigated the association between ABSI and the risk of CRC.

Therefore, this study sought to elucidate the relationship between ABSI and the incidence of CRC utilizing individual data from the National Health and Nutrition Examination Survey (NHANES) database. The objective was to investigate this correlation and formulate efficient preventative and screening measures for the incidence of CRC.

This study represents the first investigation to comprehensively analyze the relationship between ABSI and CRC in a broad population across the United States, leveraging the NHANES dataset. We additionally included and examined the most recent NHANES data from 2003 to 2023. The results indicated that ABSI is positively correlated with an increased incidence of CRC. This correlation remained significant even after taking all variables into account. In the subgroup analyses carried out according to age and BMI, a significant interaction between the ABSI and CRC was detected. In ROC analysis, we discovered that the association of ABSI with CRC exceeded that of other obesity indices, indicating that ABSI may be more precise than other obesity-related metrics in predicting CRC. The data revealed that the predictive capacity and accuracy of the ABSI for CRC were higher in individuals under 60 years of age than in those who were 60 years old or older. These findings suggest directions for further research and propose that, in clinical practice, ABSI should be considered as an auxiliary tool for risk assessment, especially for specific population subgroups such as those aged less than 60 years, and those with varying BMI categories. This would enable the formulation of more targeted preventive interventions.

Among the various factors associated with cancer development, visceral obesity is more likely to be a key carcinogenic factor than overall fat (16). Research has indicated that visceral obesity is a prevalent disease that is typically accompanied by low adiponectin levels. Moreover, it is a firmly recognized risk factor for CRC (17). This is because visceral obesity triggers a series of complex pathophysiological changes that further increase the risk of cancer (18–20). For instance, several pro-inflammatory cytokines like tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) are secreted by visceral adipose tissue (5). These cytokines keep the immune system activated continuously, thereby leading to a state of chronic inflammation. Prolonged chronic inflammation can result in recurrent damage and repair of the colorectal mucosal epithelial cells, heightening the probability of genetic alterations and hence facilitating the onset and progression of colorectal cancer (21, 22). Furthermore, adipose tissue, especially the visceral fat within it, can cause the levels of insulin and insulin-like growth factor-I (IGF-I) in the serum to go up. It can also prompt the release of leptin and adiponectin. These alterations significantly contribute to the etiology of cancer (23). Computed tomography (CT) and magnetic resonance imaging (MRI) are commonly used to measure the distribution of visceral fat. Nevertheless, these techniques are expensive, take a lot of time, and are not appropriate for large-scale epidemiologic studies (24). Consequently, a straightforward clinical anthropometric index, the ABSI, is suggested for assessing visceral fat. The ABSI is founded on the notion of anisotropic growth in calculating BMI and has successfully developed BMI-independent alternatives to waist indices (10). From a statistical perspective, the ABSI has no dependence on height, BMI, and WC, and more accurately represents visceral adiposity than conventional anthropometric measures. Anthropometric measurements more accurately represent visceral obesity compared to conventional anthropometric assessments (25). In contrast to other novel anthropometric measures like the BRI, the ABSI has something to do with increased cancer risk in numerous spots (26), whereas the BRI has infrequently been connected with cancer (15). This suggests that the ABSI is more centered on measuring visceral fat, which is highly relevant to the incidence of cancer.

In recent years, the ABSI has gained increasing recognition for measuring visceral fat accumulation and its impact (27, 28). Studies have also demonstrated a positive relation between ABSI and the risk of neurological diseases (13), cardiovascular diseases (7), and all-cause mortality (29). Moreover, an increasing amount of research is exploring the connection between the ABSI and cancer risk. Studies regarding the UK Biobank cohort have shown that ABSI is markedly linked to a greater risk of five particular malignancies, among which are lung cancer and CRC, and the overall risk of developing cancer as well (26). A cohort research from the Guangzhou Biobank in China, with a 14-year follow-up, manifested a positive linkage between ABSI and an augmented risk of CRC (30). An analysis that combined and involved collaboration of 11 Australian cohorts showed that ABSI correlates with total cancer and CRC in both genders, but not with prostate cancer (31). Nevertheless, research on the American NHANES database finds that higher ABSI levels are closely linked to prostate cancer risk and its related death rates (25, 32). This indicates that ABSI may be subject to certain limitations when directly applied to populations with different ethical backgrounds, and the current evidence regarding the relationship of ABSI to CRC remains comparatively limited. Consequently, we undertook a comprehensive examination of the relationship between ABSI and CRC within the American populace. Our study results show that ABSI has a positive relation with a higher risk of CRC, particularly in specific demographics where this association is more significant. Furthermore, to explore the relationship between ABSI and CRC more comprehensively, we conducted an in-depth analysis and comparison of relevant studies. A study based on NHANES data from 1999 to 2018 investigated the association between ABSI and the risk of CRC among patients with metabolic syndrome. It was found that, in this patient group, a higher ABSI was significantly associated with an increased risk of developing CRC (33). In contrast, our study, based on a broader population in the United States, has further expanded the scope of research on the relationship between ABSI and CRC. Although the research subjects differ, both studies highlight the importance of ABSI in assessing the risk of CRC. Moreover, the results of our study, to some extent, corroborate those of the previous study, indicating that ABSI may be an important predictor of CRC, not restricted by the single factor of metabolic syndrome. Christakoudi et al. revealed the association between body shape phenotypes and imaging-based body composition measurements, as well as their relationship with colon cancer (34). Their research demonstrated that body shape phenotypes defined by ABSI and hip index (HI) were closely related to body composition and could reflect differences therein, such as variations in the distribution of visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (ASAT). These differences were associated with the risk of colon cancer. Our study also detected an association between ABSI and CRC, further supporting the crucial role of body composition, especially abdominal fat distribution, in the pathogenesis of CRC. Rontogianni et al. provided new evidence for the causal relationship between body shape indices and the risk of CRC through a Mendelian randomization study (35). They discovered a potential positive causal correlation between the allometric index ABSI, waist-hip index (WHI), and CRC, which was independent of traditional waist-circumference indices and BMI. The results of our study echo theirs, further strengthening the reliability of ABSI as a risk predictor for CRC. Simultaneously, this also provides a direction for more in-depth research on causal mechanisms in the future.

In this study, we also found that the association between ABSI and CRC risk was more pronounced, especially in the subgroup of individuals under 60 years old (40–60 years old). The subgroup analysis accurately pinpointed the age range of 40–60 years old, where the association was significant, revealing the close connection between ABSI and CRC risk in this age group. In addition, the ROC analysis, as a supplementary tool for exploring the overall age-related trends in this study, showed that ABSI had a certain value in predicting CRC risk, especially in the population under 60 years old, where it exhibited high sensitivity. The results of these two analyses are closely related and refer to each other. From a more macroscopic perspective, that is, the grouping of ages ≥60 years old and < 60 years old, the ROC analysis helps us to grasp the overall trend of the predictive ability of ABSI with age, further confirming the findings of the subgroup analysis and emphasizing the importance of age as a modifying factor when considering the relationship between ABSI and CRC risk. This finding is consistent with what Krakauer et al. pointed out regarding the high correlation between ABSI and age, and is in line with previous research results, indicating that within this age range, ABSI might be an effective risk predictor (33). Specifically, the higher metabolic rate in younger people may amplify the impact of abdominal fat distribution on subsequent health outcomes (36). Additionally, unhealthy lifestyle behaviors, such as sedentary habits and poor dietary choices, are more prevalent among middle-aged individuals (37). This may further exacerbate the association between ABSI and the risk of CRC. As people age, the clinical manifestations of elderly patients tend to be more complex, often accompanied by multiple comorbidities. In this age group, the influence of ABSI still exists, but it may be masked by other factors, such as genetic factors and past medical history. Elderly patients may experience vague symptoms such as weight loss and decreased appetite, which are often attributed to aging rather than cancer (30). This thus influences the correlation between ABSI and CRC. These combined factors can explain the differences in the strength of the association between ABSI and CRC observed in different age subgroups.

To date, no study has explored the correlation between ABSI and the risk of CRC in the general population of the United States. The large sample size is another advantage of this study. However, we cannot overlook the limitations of the research. This study was conducted based on the cross-sectional survey data of NHANES. This approach may introduce temporal bias in the reference time points between anthropometric measurements and CRC. The relationship between anthropometric data and the risk of CRC may change over time, and the cross-sectional design restricts the ability to clarify causal relationships. Thus, it is impossible to rule out the possibility of reverse causation or bidirectional causation. Secondly, even after adjusting for some potential confounding variables in the statistical analysis, there may still be undetected confounding factors, which could affect the accuracy of the results. Finally, NHANES did not collect imaging and pathological data from its participants. Therefore, relying on self-reported CRC data may introduce information bias. Especially among the elderly population, due to memory decline, insufficient disease awareness, or limited access to medical care, they may not accurately report their CRC status, leading to an underestimation of the number of CRC cases and thus affecting the accuracy of the research results. Future research should adopt more objective cancer diagnosis methods, such as integrating clinical examination data and medical records, to reduce the bias caused by self-reporting. Meanwhile, more detailed survey plans can be designed for different age groups to improve the accuracy of the data.

This study finds that a bigger ABSI is tied to a higher CRC risk, especially for people under 60 years of age (40–60 years) and those with different BMI types. Compared to traditional anthropometric measurements, ABSI has a unique value in predicting CRC. Notably, it shows enhanced sensitivity in those aged less than 60 years. Future studies should the precise mechanisms of ABSI and CRC to formulate novel strategies for decreasing incidence rates. Furthermore, public health education must be enhanced to promote food regulation, consistent physical activity to diminish visceral fat buildup, and the endorsement of healthy lifestyles to mitigate the risk of CRC.