The Hunger Hormone, Ghrelin
Ghrelin is a hormone that circulates throughout our body, but is mostly produced by certain cells in our stomach. Ghrelin is produced by these cells in the stomach and then a chemical message is sent to the brain to initiate eating (or desire to eat). Ghrelin is associated with regulating mealtime hunger and meal initiation. We have found that ghrelin has many roles; it causes a mild inflammatory response and dilates our blood vessels, it affects our regulation of insulin and glucose, but ghrelin is mostly known as the “hunger hormone.”
Ghrelin is unique because it is the only hormone proven to be a strong appetite stimulant. Ghrelin infusions have been used in the past to stimulate appetite in cancer patients. There has been a lot of research regarding how altering ghrelin levels plays a role in bariatric surgery. What we do know is that ghrelin is increased in our circulation just prior to a meal. In lean subjects, ghrelin levels fall immediately following food ingestion. In obese subjects, ghrelin levels did not fall in similar fashion following food ingestion. Many studies have shown that perhaps this is why people may become obese. If ghrelin levels do not fall, you will not feel full and your desire to keep eating will remain the same.
Interestingly, diet-induced weight loss is associated with an increase in ghrelin levels. Bariatric surgery operations that remove the major source for ghrelin (sleeve gastrectomy)or separate the course of food from all but a small pouch of stomach (gastric bypass) cause a dramatic reduction in ghrelin levels. In turn your level of satiety (fullness after eating) is increased and you are snacking and grazing less. You are simply just not hungry like you were prior to surgery. We do expect you to still have hunger after surgery. Being hungry is NORMAL- the point of surgery is to not take away your appetite completely. But you should feel much less hungry than you did prior to surgery.
Currently there is no other known way to decrease ghrelin levels other than surgical procedures. This area has widely been researched. Altering ghrelin without surgery is something that researchers plan to discover for the future but currently there is no medication that has been shown to alter ghrelin levels effectively.