The Appetite Suppressant of Ghrelin Hunger Hormone

June 10, 2016

Have you ever thought about what makes you feel hungry or full? There are many signals in our body that help to control the amount of food we eat. Ghrelin, which is sometimes called the hunger hormone, is one of these signals.

What is Ghrelin and What Does It Do?

Ghrelin is a hormone that increases hunger feelings. It is important for controlling appetite in humans.

Ghrelin is made and released by cells located in the upper part of the stomach. When the stomach is empty, ghrelin travels through the bloodstream and tells the brain to signal hunger. After eating, the stomach stops releasing ghrelin into the bloodstream. This gives a person a sense of fullness and tells one to stop eating. Ghrelin levels will change throughout the day. They are high just before you eat a meal, letting you know that you are hungry. Levels are low just after eating, letting you know that you are full and to stop eating.

When you eat less food through dieting, your ghrelin increases to high levels which tell the brain to make you feel hungrier than normal. This is your body’s attempt to make you eat more and slow weight loss. That is part of the reason why people tend to feel hungrier during weight-loss diets. On the other hand, overeating decreases ghrelin to lower levels which result in less hunger, a sense of fullness, and decrease the urge to eat. People with stable weights have fewer changes in their ghrelin levels and a more balanced sense of hunger and fullness throughout the day. They neither eat too few calories such that they lose weight nor too many calories such that they gain weight – the result is a stable weight.

Why Does Bariatric Surgery Impact Ghrelin Levels?

Weight loss or bariatric surgery is also called metabolic surgery. These surgeries affect the body’s metabolism by changing stomach and intestinal hormone levels including ghrelin (1).

The most common metabolic and bariatric procedures are the Roux-en-Y Gastric Bypass and the Sleeve Gastrectomy. Since these surgeries change the stomach in different ways, they have different impacts on ghrelin.

In the Roux-en-Y Gastric Bypass, a small stomach pouch is separated from the upper part of the stomach where ghrelin is produced and released. After surgery, food goes through the small stomach pouch and it doesn’t contact the ghrelin-producing part of the stomach. Some research suggests that ghrelin levels decrease after gastric bypass surgery. This may be due to food having less contact with the ghrelin-producing part of the stomach.  Other research studies show that ghrelin levels don’t change after gastric bypass surgery (2-5). It is not clear why some researchers have found that ghrelin levels decrease after Gastric Bypass surgery while others find no change in ghrelin. More research is needed to clarify this issue.

In the Sleeve Gastrectomy, up to 90% of the stomach is removed from the body. This includes removing most of the stomach cells that produce ghrelin. As a result, the stomach’s ability to release ghrelin is greatly reduced. Research studies consistently show that ghrelin levels decrease after Sleeve Gastrectomy (1, 6-7). The exact amount of stomach removed varies from person to person which affects how much ghrelin is decreased after sleeve gastrectomy (8). It is possible that the ghrelin-producing cells of the remaining stomach may grow back over time so we don’t know if the decreased ghrelin levels seen right after Sleeve Gastrectomy will last forever.

Do Ghrelin Levels Affect Weight Loss?

Most researchers agree that the decrease in ghrelin levels after metabolic and bariatric surgery will help with short term weight loss because people feel less hungry. However, it should be kept in mind that there are many reasons why people lose weight after such surgery, which may have nothing to do with lower ghrelin levels. That’s why it is not surprising that research studies don’t show a consistent link between ghrelin levels and the amount of weight loss. People can still have good weight loss results after surgery even if their ghrelin levels don’t change. Ghrelin may be important in weight loss but is just one piece of a very complicated puzzle.

Your diet and surgery aren’t the only things that affect ghrelin. Research has shown that sleep patterns impact ghrelin too. Have you ever felt extra hungry or noticed more cravings after a night of poor sleep? Sleep-deprived adults tend to have higher ghrelin levels, more hunger, and less feeling of fullness compared to adults who get enough sleep (9). Getting 7 to 9 hours of sleep each night may help to prevent increases in ghrelin levels, and the drive to eat more which may result in weight gain.

Summary

Ghrelin is a hormone that increases hunger. Metabolic and bariatric surgeries, like the Roux-en-Y Gastric Bypass and Sleeve Gastrectomy, can lower ghrelin levels by changing the structure of the stomach. Having lower ghrelin levels makes people feel less hungry which can help with short-term weight loss. However, this is just one of the many changes after metabolic and bariatric surgery and people can still have good weight loss results even if their ghrelin levels don’t change.

Resources

1. Tymitz K, Engel A, McDonough S, Hendy MP, Kerlakian G. Changes in ghrelin levels following bariatric surgery: review of the literature. Obes Surg. 2011;21:125–30.
2. Cummings DE, Weigle DS, Frayo RS, Breen PA, Ma MK, Dellinger EP, Purnell JQ. Plasma ghrelin levels after diet-induced weight loss or gastric bypass surgery. N Engl J Med. 2002;346:1623–30.
3. Geloneze B, Tambascia MA, Pilla VF, Geloneze SR, Repetto EM, Pareja JC. Ghrelin: a gut-brain hormone: effect of gastric bypass surgery. Obes Surg. 2003;13:17–22.
4. Couce ME, Cottam D, Esplen J, Schauer P, Burguera B. Is ghrelin the culprit for weight loss after gastric bypass surgery? A negative answer. Obes Surg. 2006;16:870–8.
5. Holdstock C, Engström BE, Ohrvall M, Lind L, Sundbom M, Karlsson FA. Ghrelin and adipose tissue regulatory peptides: effect of gastric bypass surgery in obese humans. J Clin Endocrinol Metab. 2003;88:3177–83.
6. Langer FB, Reza Hoda MA, Bohdjalian A, Felberbauer FX, Zacherl J, Wenzl E, Schindler K, Luger A, Ludvik B, Prager G. Sleeve gastrectomy and gastric banding: effects on plasma ghrelin levels. Obes Surg. 2005;15:1024–9.
7. Pournaras DJ, le Roux CW. Ghrelin and metabolic surgery. Int J Pept. 2010; http://dx.doi.org/10.1155/2010/217267

ABOUT THE AUTHOR Malcolm K. Robinson, MD, FACS, is a surgeon and the director of Metabolic Support Services at Brigham and Women’s Hospital and an assistant professor of surgery at Harvard Medical School. Dr. Robinson received his college degree from Harvard University and medical degree from Harvard Medical School. He completed his surgical residency and advanced fellowships in nutrition and general surgery at Brigham and Women’s Hospital. He has been performing surgery for over 20 years and works primarily with bariatric surgery patients.

ABOUT THE AUTHOR Laura Andromalos MS RD LDN CDE has been helping bariatric surgery patients achieve their health goals since 2009. She enjoys supporting patients through the life-changing journey of bariatric surgery and educating health professionals on the field of bariatric nutrition through speaking and writing engagements. Laura is a freelance nutrition expert for many companies, including Brigham and Women’s Hospital and Orgain Protein. She holds a MS in Health Communication from Boston University, a BS in Nutritional Sciences from Cornell University, and completed her dietetic internship at Mayo Clinic Florida.

ABOUT THE AUTHOR Hassan S. Dashti, PhD, is a dietetic intern at Brigham and Women’s Hospital and a postdoctoral research fellow at Massachusetts General Hospital’s Center for Human Genetic Research/Broad Institute of MIT and Harvard. He received his Doctoral and Master’s degrees in Biochemical and Molecular Nutrition from Tufts University and his Bachelor’s degree in Molecular Genetics from the University of Pennsylvania. Dr. Dashti's research lies in the area of chronobiology, genetics and nutrition aimed at unraveling personalized dietary recommendations to attenuate risk for cardiometabolic diseases.

---