Fasting respiratory exchange ratio (RER) was significantly higher in the T2D patients (0.82±0.03 vs. 0.79±0.03, p<0.01) and significantly lower upon insulin stimulation (0.87±0.04 vs. 0.89±0.04, p<0.05) compared with age-and BMI-matched controls. Here, INS is linked to type 2 diabetes mellitus.