The principal finding in this study was that BMI correlated negatively with the mRNA abundance for three amino acid NTs (TauT, ASCT2, and LAT1) in the jejunum from patients with morbid obesity undergoing a Roux-en-Y gastric bypass, and positively correlated mRNA abundance for the high-affinity short-chain fatty/monocarboxylate acid transporter SMCT1. We also observed positive correlations between BMI and preoperative serum concentrations of several of the short-chain fatty acids including butyric, valeric, and isocaproic acid. This evidence concerns the gene SLC6A6 and morbid obesity.