We present evidence supporting the hypothesis that postprandial upregulation of the size of the small intestine and the liver is caused by an increased blood flow volume to the organs. The postprandial response of ball pythons was characterized by measurements of oxygen consumption, organ size changes and histological evaluation of the mucosal epithelium and liver parenchyme. Synchronized with these changes in measurements were changes in the patterns of blood flow volume to small intestine and liver. A correlation analysis of organ size change and blood flow volume showed a significant nonlinear relationship, which explained about 50% of the overall variances in organ size (small intestine, liver). Histological analysis indicated that incorporation of lipid droplets in enterocytes and in hepatocytes contributes to an increase of absorptive surface magnification (in small intestine) and hepatocyte size (in liver). Collectively, these data support the concept that in the ball python, postprandial upregulation of organ size does not reflect new mitotic activity, but rather results from increased blood volume in the intestinal villi and incorporation of lipid droplets into enterocytes and hepatocytes, respectively.