Figure 1.

Study Protocol

Following an overnight fast, 16 healthy, normal-weight subjects each received the following interventions, in random order, over 5 separate study days in a single-blinded fashion: (1) 90 min saline infusion (fasted saline, control visit); (2) standard breakfast, then 90 min saline infusion (fed saline); (3) 90 min PYY_3-36 infusion at 0.3 pmol/kg/min; (4) 90 min GLP-1_{7-36 amide} infusion at 0.8 pmol/kg/min; (5) 90 min combined PYY_3-36 and GLP-1_{7-36 amide} infusion, at 0.3 pmol/kg/min and 0.8 pmol/kg/min, respectively. On each visit, subjects underwent a 60 min fMRI scan, which commenced 20 min after the start of the infusion. During the fMRI scan, a picture processing task was performed where images of food and nonfood were shown. The mean percent change in BOLD signal in prespecified brain ROIs when viewing images of food compared to nonfood were determined for each study day. An ad libitum buffet meal was served immediately after the infusion on all study days in order to measure energy intake. Blood sampling (for PYY_3-36 and GLP-1_{7-36 amide}) and assessments of appetite (based on VAS after direct questioning) was performed. One subject was excluded from analysis due to excessive head movement during the scans, leaving data from 15 subjects for analysis.