Ghrelin is an aminoacid produced in the stomach, especially in the portion known as gastric fundus, found in the upper part of the organ. It is also produced by the first portion of the small intestine (duodenum). This aminoacid is a hormone known as orexigenic (stimulates appetite).
What is ghrelin and how it works?
When the hormone ghrelin is released, signals are sent to our brain in order to make the person feel the urge to eat in search of satiety sensation. In many obese patients, ghrelin secretion levels are altered and this consequently makes them feel they need to eat more than they actually really require. We explain in depth below.
The levels of this hormone are increased before food intake and subsequently decrease in proportion to the amount of calorie intake; ghrelin levels increase when a person is dieting and this is why it plays a very important role in the long-term regulation of body weight since patients undergoing diets suffer to maintain them over long periods of time.
What happens with obese individuals is that ghrelin levels are relatively low even when they have not eaten and these levels remain low even after eating. In other words changes in ghrelin levels in obese patients are less marked or intense than with normal weight people after food intake so the appetite sensation persists or returns sooner despite having eaten enough food.
How ghrelin affects weight gain?
Ghrelin is produced when the stomach is empty and during times of negative energy balance such as low calorie diets, chronic exercise and anorexia nervosa, this partly explains why a person who goes on a diet feels so hungry: the concentrations of ghrelin rise before meals, stimulating appetite sensation and decrease after food intake.
How does gastric sleeve surgery affects ghrelin production?
While several bariatric procedures are limited to restrict the amount of food a person can eat at certain moment, the gastric sleeve surgery (like other procedures eg: gastric bypass) reduces the amount of ghrelin, which is produced in the stomach portion that is removed from the body and includes almost the entire gastric fundus, place where the main production of ghrelin takes place; it is calculated that the gastric fundus contains 10 to 20 times more ghrelin per gram of tissue of the organ than what is found in the duodenum the next major ghrelin source in the body.
Gastric sleeve surgery patients unlike other procedures like gastric banding, gastric plication, gastric balloon, etc. not only will they eat less because the capacity of the stomach is reduced by approximately 70% but also will feel more satiety between meals, so it's a great combination to combat the "appetite attacks" or “hunger pangs” and thus they will achieve adequate and sustained weight loss until they reach a weight closer to the ideal body weight. In other words after the gastric sleeve surgery the patient has less appetite and satiety is obtained earlier and will last for a longer period of time.
It has been found that blood ghrelin levels decrease significantly in patients undergoing gastric sleeve, this decrease is presented from the first postoperative day and lasts for more than 24 months after surgery unlike patients operated from procedures such as gastric band which have increased ghrelin levels in the same periods of time.
That is why the gastric sleeve surgery excess weight loss can be up to about 60% in only 6 to 18 months after surgery, unlike the gastric band in which the loss is highly variable and ranges from only 20 to 50% loss of excess weight at best.
Lee H, I C, S Koshy, Teixeira JA, Pi-Sunyer FX, Laferrere B. Does ghrelin really matter after bariatric surgery? Surg Obes Relat Dis. 2006; 2 (5): 538-548.
Ghrelin and Gastric Bypass
There is some controversy regarding this issue as there are studies that suggest that patients undergoing gastric bypass also experience an important and significant decrease in blood ghrelin levels. However, there are other studies that contradict this statement, ensuring that gastric bypass patients do not experience changes in their levels because that procedure does not involves the resection of (taken out of the body) any portion of the stomach, but it is only sectioned and left within the body, in other words as the name implies it "bypasses" the gastrointestinal tract.
SN Karamanakos, K. Vagenas, F. Kalfarentzos, and TK Alexandrides, "Weight loss, appetite suppression, and Changes in fasting and postprandial ghrelin and peptide YY levels after Roux-en-Y gastric bypass and sleeve gastrectomy: a prospective, double blind study, "Annals of Surgery, vol. 247, no. 3, pp. 401-407, 2008. View at Google Scholar
Peterli R., B. Wölnerhanssen, T. Peters, et al., "Improvement in glucose metabolism after bariatric surgery: comparison of laparoscopic Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy: a prospective randomized trial," Annals of Surgery, vol. 250, no. 2, pp. 234-241, 2009. View at Publisher · View at Google Scholar · View at PubMed
What do patients really experience after surgery gastric sleeve in relation to the appetite?
Ultimately the most important of all, putting aside studies, statistics and hormones is what the gastric sleeve patient experiences in the postoperative period and based on the experiences of our patients, we can summarize it as follows, considering that each person is different and the experience may vary considerably.
There are gastric sleeve patients who immediately after being operated notice a significant change in the intensity of hunger, in other words they don’t feel appetite for months so they even have to set an alarm to remind them it's time for one of their 3 to 5 meals of the day.
It seems incredible that someone who used to be hungry all the time find him/herself in this situation, but once we know more about ghrelin hormone it is something that makes perfect sense and we could corroborate personally thanks to feedback from our bariatric surgery patients at ObesityFree.
On the other hand there are patients (we could say that the majority) that describe a different appetite sensation in comparison to what they used to perceive before surgery, so they do not stop feeling hungry when it's been several hours without eating, but that sensation is no longer as intense and unpleasant but simply tells them it is time to eat something.
This allows them to be more aware and controlled in order to make appropriate food choices and to eat slowly and in the correct amounts. It is also worth mentioning that during the early postoperative period, when they start solid food intake, a lot of patients have not reached the key point to know their new stomach and have not changed their “mental and emotional” relationship with food so they may initially “over-eat” and suffer from nausea and / or vomiting (by over-eating we mean that instead of having 4 bites of food they eat 5 or 6). This is perfectly normal since they are in the process of knowing their new stomach and its new boundaries/capacity limits.
This is similar to when an infant passes into solid in the foods stage process: they must learn to eat. And this is precisely the key moment in making all possible efforts and changes not only in the quality and quantity of food but also in the mental and emotional aspect, everything with the goal that over the years, the weight loss can be maintained, because if the patient does not take advantage efficiently of this valuable period of change that lasts about 18 months, they can possibly gain weight back. As we have mentioned in other articles on our blog, there is no flawless bariatric procedure with guaranteed permanent results, patients who do not make the effort to change their habits will end up boycotting the important and valuable tool / investment the gastric sleeve represents.
We must consider that there is no physical change alone in the complex system involving bariatric surgery that can overcome the evil of "mental or emotional" hunger, this is a learned behavior, a battle based on good habits, it requires a strong will power and support of the loved ones to have long term success!
Other ghrelin features to be investigated
In addition to changes in ghrelin levels due to gastric sleeve surgery, there are other hormones that come into play, some which help with satiety (eg: leptin), decreased appetite and glucose control.
Although there is insufficient evidence of all the mechanisms by which gastric sleeve surgery achieves such great weight loss results, the above proves that this surgery is not only restrictive but also shows metabolic changes. In addition, ghrelin may represent an alternate or complementary endocrine mediator in diabetes remission since it is related to metabolic syndrome, obesity, insulin resistance and insulin secretion capacity. In simple terms it is believed that ghrelin plays an important role not only in suppressing appetite but in terms of performance in the control of metabolic diseases.
The role of ghrelin in the success of bariatric surgery and gastric sleeve is still under investigation and it is known that there are other gastrointestinal hormones that play a key role in appetite control. However the above hypothesis that ghrelin also has an important role on the patient from a metabolic point of view is not only attributed exclusively to the restriction or malabsorption as previously thought, since weight loss and type 2 diabetes remission (cure) after these procedures is evident.
It has even discovered that ghrelin plays a role not only in glucose metabolism but also protecting from depression stress, quality and duration of sleep and other aspects that are to be proven, so somehow it's good that after the gastric sleeve surgery there are still circulating hormone levels.
Finally, we have seen in some forums that there are bariatric practices that tell the patient that if they want all ghrelin removed during surgery they will have to make an extra payment, it is totally unacceptable because ghrelin is necessary even in small quantities and it is actually impossible to achieve this complete ghrelin removal. We strongly recommend you to search for a serious and competent bariatric group that looks for patient’s well being and don't put your life at risk by looking for a cheaper final cost.
Written by: Gabriel Rosales
Dr. Gabriel Rosales is a highly skilled, board certified surgeon in constant pursuit of learning the latest innovations in the weight loss surgery field to give his patients the best care possible.