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

<strong>Background</strong>: Gastric cancer (GC) shows sex difference which also affects body mass index (BMI). The aim of this study was to investigate that the effect of BMI on the GC risk could be different depending on sex. <strong>Methods</strong>: The cohort was consisted of 341,002 Koreans (≥40 years) from the National Health Insurance Service–Health Screening Cohort with a median follow-up period of 12 years. Subjects were classified into five groups according to BMI. The effect of BMI was evaluated using the Cox proportional hazard regression. In addition, stratification analysis according to waist circumference (WC) was performed. <strong>Results</strong>: An increased risk of developing GC was observed in total population in obesity group (BMI 25.0-29.9 kg/m², hazard ratio [HR] 1.11, 95% confidence interval [CI] 1.03-1.20) and severe obesity group (BMI ≥30.0kg/m², HR 1.21, 95% CI 1.00-1.46) with consideration of 2-year latency period. In particular, the increase of GC risk was more pronounced in obesity group in females and in severe obesity group in males. Meanwhile, in the stratification analysis according to age, underweight (BMI &lt;18.5 kg/m²) was also found to be associated with the risk of developing GC in adults under the age of 50 (HR 5.82, 95% CI 1.17-29.00). In addition, highly obese males with high WC (≥90 cm) showed significant increase in GC risk (HR 1.45, 95% CI 1.10-1.91). <strong>Conclusions</strong>: These results suggest that there is a positive association between excess body weight and the risk of GC in Koreans, especially in highly obese males with high WC.