Ghrelin is mostly known as the hunger hormone, but it has many more functions than this alone.
Ghrelin is a peptide hormone primarily produced by the stomach. Ghrelin is secreted by the stomach when it is empty and increases your appetite, sending a message to your brain that you need to eat. This message is sent through your bloodstream or signals via the vagus nerve to your brain.
It has been said that too much ghrelin makes your body crave fatty and sugary foods. In saying this, Dr. Mauro Di Pasquale, mentions a study where low carb, high fat intake reduced ghrelin levels, and as such decreased appetite and fat formation. He says that this is one of the ways that the body limits fat formation on a high fat diet.
Things that can increase ghrelin levels include:
Lack of sleep
Fasting
Chronic stress
Ghrelin signaling increases food intake, fat storage, and reduces thermogenesis and reduces energy expenditure. So, you want to control ghrelin levels as much as possible if on a fat loss diet or even to maintain your current body weight.
How can you control ghrelin levels?
Get enough sleep, ensure optimal amounts of protein, increase muscle mass, avoid excess sugar, eat regular meals / don’t fast for too long, and use refeed meals strategically. Refeed meals will ensure you aren’t low calorie for too long and will help increase leptin levels.
The major biological functions of ghrelin include:
the secretion of growth hormone,
the stimulation of appetite and food intake,
the modulation of gastric acid secretion and motility,
and the modulation of the endocrine and exocrine pancreatic secretions.
Ghrelin also exerts wide physiological actions throughout the body including: inflammatory functions, glucose homeostasis, reproductive functions, cardiovascular function, and bone formation.
The clinical applications of ghrelin have been investigated in both eating disorders and muscle wasting conditions, including obesity, anorexia, cachexia, and sarcopenia (muscle wasting due to aging).
“Ghrelin can indirectly increase muscle mass by increasing food intake and activating the GH/Insulin-like growth factor-1 (IGF-1) axis in cachexic mice”.
Ghrelin has multiple beneficial effects on cardiovascular functions, thereby improving cardiovascular disease risk. Ghrelin improves the survival prognosis of myocardial infarction by reducing sympathetic nerve activity. “Overall, ghrelin treatment may reduce cardiac sympathetic nerve activity (CSNA) inflammation and oxidative stress in the heart, and induce angiogenesis. More studies are needed to further assess whether ghrelin is beneficial for treating heart diseases.” They are looking into the usefulness of ghrelin analogues to find out more about any potential benefits.
Ghrelin exerts many anti-inflammatory actions in inflammatory bowel disease, pancreatitis, sepsis, arthritis, and diabetic nephropathy.
“Several synthetic ghrelin mimetics are being pursued in clinical trials for diverse indications. Three compounds are currently in development. Macimorelin is in clinical trials for the diagnosis of GH deficiency. A second compound, anamorelin, is in clinical trials for the treatment of cancer cachexia. A third compound, relamorelin (also known as RM-131) is currently in phase II clinical trials and is being developed for treatment of diabetic gastroparesis and other gastrointestinal (GI) disorders.”
A concern with ghrelin though is its link to cancer development and progression. “Ghrelin and GHS-R have been detected in many endocrine and non-endocrine tumors (21, 22), suggesting that the ghrelin/GHS-R axis might be associated with tumor growth and progression. In pituitary tumors, ghrelin mRNA is detected in non-functional adenomas, GH- and gonadotropin-producing adenomas and prolactinomas, with highest GHS-R expression detected in the GH-producing adenomas”. It has also been linked with breast cancer as well.
References:
Amino acids and proteins for the athlete – Dr. Mauro Di Pasquale