Obesity and colorectal cancer risk: A systematic review and meta-analysis.

BACKGROUND: An observed correlation between increased colorectal cancer (CRC) incidence in patients with obesity [body mass index (BMI) ≥ 30 kg/m2] has been identified in past literature. However, there has been limited data in recent decades. This, along with a dramatic global increase in obesity rates, exposure to environmental and lifestyle risk factors for CRC development, and large updates to the proposed biological mechanisms underpinning this relationship, warrants an updated review of recent data between CRC and obesity. AIM: To determine if an updated correlation exists between obesity and the risk of CRC development. METHODS: We evaluated recent data, synthesising pooled estimate effects to determine if an updated correlation exists between obesity and CRC. Observational studies were identified from a range of databases (PubMed, EMBASE, Scopus and the Cochrane database). From the studies identified, sex-stratified meta-analyses were conducted. Additionally, studies included in this review that were unfit for meta-analysis underwent qualitative analysis. RESULTS: In a pooled sample size of 83506 male participants obtained from six observational studies, a significant positive correlation between obesity and CRC incidence was identified with a hazard ratio (HR) of 1.71 [95% confidence interval (CI): 1.44-2.02]. A pooled sample size of 152043 female participants from six observational studies also revealed a positive correlation with an HR effect of 1.26 (95%CI: 1.03-1.53). Qualitative analysis of studies not included in the meta-analysis consistently supported this relationship for both sexes. CONCLUSION: Obesity, diagnosed by a BMI ≥ 30 kg/m2, significantly increases the risk of CRC incidence compared to those of a healthy BMI underscoring the importance of focused strategies to prevent obesity as a modifiable risk factor to reduce CRC incidence.