Effect of body mass index on gastric cancer risk according to sex in Korea: a nationwide cohort study and literature review.

Gastric cancer (GC) demonstrates a sex disparity that may also be associated with body mass index (BMI). This study explored whether the effect of BMI on the risk of GC varies by sex. The study cohort included 341,999 Koreans aged 40 years or older from the National Health Insurance Service-Health Screening Cohort, with a median follow-up period of 10 years. Participants were categorized into five groups based on their BMI. The effect of BMI was evaluated using Cox proportional hazard regression. Additionally, stratification analysis was performed according to waist circumference. An increased risk of developing GC was observed across the study population among those with obesity (BMI 25.0-29.9 kg/m; hazard ratio [HR], 1.11; 95% CI , 1.03-1.20) and severe obesity (BMI ≥30.0 kg/m; HR, 1.22; 95% CI, 1.01-1.47), considering a 2-year latency period. Notably, the rise in GC risk was particularly pronounced among women with obesity and men with severe obesity. In the age-stratified analysis, severe obesity (BMI ≥30.0 kg/m) was associated with an increased risk of GC in men under 50 years old (HR, 1.83; 95% CI, 0.99-3.37). For individuals aged ≥50 years, obesity was linked to a heightened risk of GC in both sexes. Furthermore, normal BMI (18.5-22.9 kg/m) was associated with an increased GC risk in women. These findings indicate a positive association between excess body weight and the risk of GC in Koreans, particularly among men with severe obesity.