AIM: To investigate the role of the duodenum in the regulation of plasma ghrelin levels and body mass index (BMI), and the correlation between them after subtotal gastrectomy.METHODS: Forty-two patients with To-1No-1M0 gastric cancer were divided into two groups after gastrectomy according to digestive reconstruction pattern,Billroth I group (n = 23) and Billroth Ⅱ group (n = 19).Ghrelin levels were determined with radioimmunoassay (RIA) before and on d 1, 7, 30 and 360 after gastrectomy,and BMI was also measured.RESULTS: The two groups had identical postoperative trends in ghrelin alterations during the early stage, both decreasing sharply to a nadir on d 1 (36.7% vs 35.7%),then markedly increasing on d 7 (51.0% vs 51.1%). On d 30, ghrelin levels in the Billroth I group were slightly higher than those in the Billroth Ⅱ group. However,those of the Billroth I group recovered to 93.6% on d 360, which approached, although lower than, the preoperative levels, and no statistically significant difference was observed. Those of the Billroth Ⅱ group recovered to only 81.6% and manifested significant discrepancy with preoperative levels (P = 0.033).Compared with preoperative levels, ghrelin levels of the two groups decreased by 6.9% and 18.4% and BMI fell by 3.3% and 6.4%, respectively. The linear regression correlations were revealed in both groups between decrease of ghrelin level and BMI (R12 = 0.297, P = 0.007;R22 = 0.559, P < 0.001).CONCLUSION: Anatomically and physiologically, the duodenum compensatively promotes ghrelin recovery and accordingly enhances BMI after gastrectomy.Regarding patients with insufficient ghrelin secretion,ghrelin is positively associated with BMI.