Your weight is controlled, in part, by your brain. There is a complex feedback system that lets your brain know how much energy you have stored — and a hardwired drive to eat when your brain thinks you need more food.
This article dives into the science of ghrelin, a hormone involved in the appetite control system. We will explore how ghrelin controls appetite and then explain the genetic variants that link ghrelin to weight gain.
What is ghrelin?
Ghrelin is a peptide hormone that stimulates appetite and regulates metabolism. It drives us to seek out food and eat.
At the most basic level, we are all driven to seek out food. The motivation to eat is inherent to all animals because we simply can’t live without energy from food.
Tasty foods like Doritos and pizza haven’t always been at our fingertips. Our ancestors had to eat to survive. Thus, the innate drive to eat is strong enough to drive people to eat less tasty foods, such as liver, insects, or turnips. This is where ghrelin comes in, prompting us to eat to survive.
Ghrelin was discovered about 20 years ago and first investigated as a hormone controlling the release of growth hormone (GH). Over the past decade, research shows that ghrelin stimulates appetite.[ref]
What causes ghrelin to rise and fall?
The cells lining the stomach secrete ghrelin, and then the hormone travels to the brain.
In the hypothalamus, ghrelin receptors (GHSR receptors) receive the signal for the need for food. This triggers a series of actions that result in you seeking food.[ref]
At the same time, ghrelin causes the stomach to prepare for food in two ways:
- through increasing gastric motility (e.g., stomach growling because you are hungry)
- increasing stomach acid
Thus – the signal sent to the brain prompts you to seek food, and the signal sent to the stomach gets it ready for action.
What triggers ghrelin to be released?
Both hypoglycemia (low blood glucose levels) and low body weight can act to trigger ghrelin.
Fasting increases this hormone and eating – physically filling up the stomach – decreases it.
Researchers don’t have all the answers yet for ghrelin, and there is a lot of ongoing research into the link with BMI, cardiovascular health, and aging.[ref]
Leptin vs. Ghrelin:
Leptin is another hormone that is linked to appetite and weight. It is the counterbalance to ghrelin. Leptin is like the ‘stop’ signal to let you know that you’re full. Just like with ghrelin, there are genetic polymorphisms in the leptin receptor gene that are linked to weight gain.
Ghrelin Genotype Report:
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GHRL gene:
GHRL is the gene that “encodes the ghrelin-obestatin preproprotein that is cleaved to yield two peptides, ghrelin and obestatin.”[ref] There are several polymorphisms in the GHRL gene that have been studied in reference to obesity and appetite.
Check your genetic data for rs4684677 (23andMe v4, v5):
- A/A: slightly increased risk of obesity, metabolic syndrome[ref][ref]
- A/T: slightly increased risk of obesity
- T/T: typical
Members: Your genotype for rs4684677 is —.
Check your genetic data for rs35683 (23andMe v4; AncestryDNA):
- A/A: slightly increased risk of obesity[ref]
- A/C: slightly increased risk of obesity
- C/C: typical
Members: Your genotype for rs35683 is —.
How big is the impact of these two variants on obesity? While it may depend on the population being studied, most of the studies show the impact of the GHRL variants is not all that great. They add to the risk of obesity, but the increase in risk isn’t huge.[ref]
GHSR – Ghrelin receptor:
The GHSR gene codes for the Growth Hormone Secretagogue Receptor, which is the receptor for the ghrelin hormone.
Check your genetic data for rs572169 (23andMe v4, v5; AncestryDNA):
- T/T: increased risk of obesity[ref][ref]; increased height in children[ref]
- C/T: increased risk of obesity, increased height
- C/C: typical
Members: Your genotype for rs572169 is —.
CLOCK gene:
The CLOCK gene codes for a protein that is part of our innate circadian rhythm mechanism. Circadian rhythm plays a big role in metabolism, weight, appetite, sleep, mood, and overall health.
Related article: Circadian rhythm (CLOCK gene) and weight loss
Check your genetic data for rs1801260 (23andMe v4, v5; AncestryDNA):
- G/G: evening chronotype; higher average ghrelin levels, more resistant to weight loss[ref][ref]
- A/G: evening chronotype; higher average ghrelin levels, more resistant to weight loss
- A/A: typical
Members: Your genotype for rs1801260 is —.
Lifehacks for suppressing ghrelin:
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