Fifteen lean [BMI(body mass index) less than 23 kg/m2] type 2 diabetes subjects and fifteen obese (BMI more than 26 kg/m2) subjects with type 2 diabetes treated by diet and/or metformin, SU(sulfonylurea), DPP4-inhibitors(Dipeptidyl peptidase-4 inhibitor) will be recruited. Every subject will be studied on 2 separate days in random order with 1-2 week intervals. These participants will be injected either normal saline or 10 mcg of lixisenatide in a cross-over fashion. Neuroimaging composed with resting-12-min, visual stimulation task-12-min, T1-5-min, and diffusion tensor image-12-min will be proceeded. Ad lib buffet will be provided to every participant and the intake will be measured. Surveys about appetite and mood will be done before and after neuroimaging test and buffet eating.