Ghrelin levels increase after pictures showing food

The neuropeptide ghrelin is a major signal for food intake in various species including humans. After exogenous ghrelin administration, food intake and body weight increase in rodents. In normal human subjects, ghrelin administration increases self-rated appetite and calorie intake and prompts the imagination of favorite meals. It is unclear so far whether ghrelin levels are affected by external cues such as sight of food. We investigated the influence of pictures showing food compared to neutral pictures on ghrelin levels in young normal male subjects (n = 8). The study consisted of two consecutive sessions with a one-week interval. During each session, blood for later analysis of plasma concentrations of ghrelin was collected between 08:15 and 13:00 every 15 min (between 10:30 and 11:30 every 10 min). Breakfast and lunch was provided at 08:30 and 12:00, respectively. Fifty pictures were presented from 10:30 to 10:45 showing neutral images during the first session and food contents during the second session. As expected, ghrelin levels increased before each meal independent of the picture contents. In addition, ghrelin levels during the 30-min interval following the presentation of pictures with food increased significantly compared to the 30-min interval before this presentation (area under the curve (AUC): 188 % vs. 158 %, P < 0.05). The difference in the increases between the two picture conditions was also significant (P < 0.05). Our findings suggest that sight of food elevates ghrelin levels in healthy volunteers.