So, what have we learned so far? That ghrelin production is directly related to appetite in normals, but is unpredictable in post-bariatric surgery patients. And that studies of post-surgical patients in the U.S. and Sweden showed contradictory results. So let's throw in another variable - surgical procedure - as well as another location - Greece - and see what we can add to our narrative.
First, a little background from a non-surgeon. Gastric bypass is a procedure in which the stomach is reduced in size from that of a football to that of an egg or even a walnut. The reduction is accomplished by surgically stapling a line through part of the stomach so that a large part of it is just hanging out in the belly, still producing chemicals but not available to hold food. Thus, right off the bat, the amount of food that can be consumed is significantly restricted.
Further, the gastric bypass surgeon attaches this newly created small pouch to the small intestine far enough down the line so that absorption is significantly decreased as well. The new arrangement forms a "Y" and gives the Roux-en-Y its name (Roux was the name of the surgeon who first described the procedure in the 1800's).
In contrast, the sleeve gastrectomy is a purely restrictive procedure. And you may be tipped off by the -ectomy suffix . . . a large portion of the stomach is removed. And that's it. No reversibility, no band that needs to be filled with fluid, no port infections, just a long thin stomach where a football used to be.
Researchers in Greece performed a double-blind prospective study (a reader's favorite terms) with 32 patients, 16 in each surgical group. Measurements of dependent variables were taken at 5 times: preoperatively, and then postoperatively at 1, 3, 6, and 12 months. Of course, both groups lost a significant amount of weight and enjoyed improvements in medical outcomes during that first year.
More interestingly, the patients in the gastric bypass group did not show a significant change in fasting plasma ghrelin levels in the same period. And the patients in the sleeve gastrectomy group did.
A subset of patients were also tested 2 hours after a meal, and ghrelin levels from before and after eating were compared. The patients in the sleeve gastrectomy group showed a decrease of 21.3%, a statistically significant change, and those in the Roux-en-Y group showed a 14% decrease, which was not statistically significant.
So, this study seems to suggest that there is a specific spot or area in the stomach responsible for production of ghrelin, and that sometimes that spot is removed or neutralized with surgery. Again, in bariatric surgery as in real estate, some value may be attributed to location, location, location.
Karamanakos, S., Vagenas, K., Kalfarentzos, F., & Alexandrides, T. (2008). Weight Loss, Appetite Suppression, and Changes in Fasting and Postprandial Ghrelin and Peptide-YY Levels After Roux-en-Y Gastric Bypass and Sleeve Gastrectomy Annals of Surgery, 247 (3), 401-407 DOI: 10.1097/SLA.0b013e318156f012