Our hypothesis is that decreased concentration of ghrelin after LSG is important for the decreased appetite and food intake postoperatively. We therefore expect infusion of ghrelin will increase an ad libitum food intake after LSG. We also expect that a decreased postprandial concentration of ghrelin after LSG play a role for increased insulin secretion and decreased postprandial plasma glucose concentrations after surgery.

Laparoscopic Roux-en-Y gastric bypass (LRYGB) and laparoscopic sleeve gastrectomy (LSG) are to bariatric procedure. After both procedures, a changed secretion of hormones from the gastrointestinal tract is believed to affect appetite and glucose metabolism. Studies have shown that after LRYGB, there is a significant increased secretion of GLP-1 and PYY. In contrast, a decreased secretion of ghrelin is a characteristic finding after LSG opposite post-LRYGB, where secretion of ghrelin is reported to be increased, decreased or unchanged. Ghrelin is primarily secreted from the gastric mucosa in the fasting state and decreases in response to food intake. Ghrelin stimulates food intake through appetite-regulating centers in the hypothalamus. Administration of exogenous ghrelin has been reported to stimulate appetite. In addition, ghrelin has recently been suggested also to affect glucose metabolism by inhibition of glucose-stimulated insulin secretion. Therefore the markedly decreased secretion of ghrelin could be of particular important for the decreased appetite and improved glucose tolerance seen after LSG.

Inclusion Criteria:

• The Danish national inclusion criteria for bariatric surgery
• Signed written informed consent
• Fasting plasma glucose <6.1 mmol/l

Exclusion Criteria:

• Pregnancy or breastfeeding.
• Hemoglobin <6.5 mM
• Newly emerged serious disease

The study visits will be performed in randomized orders and participants will not now if they will receive ghrelin or saline.