Although the oral glucose load tended to increase plasma levels of GLP-1 mainly at 30 and 120 min in all the experimental groups, obese patients with T2D had lower GLP-1 concentrations than lean volunteers at baseline (3.08 ± 0.55 vs. 2.07 ± 0.13 pmol/L, p = 0.019) and after 120 min (4.19 ± 0.78 vs. 2.30 ± 0.08 pmol/L, p = 0.004). The gene discussed is GLP1R; the disease is type 2 diabetes mellitus.