Hormones are a hot topic in the health blogosphere. This post is going to explain what different hunger hormones are, and what they do. Please note this is not an exhaustive list, but rather, a brief overview of those commonly discussed in colloquial and health-related literature to help you understand what exactly they do to help keep you maintaining the gloriousness that is homeostasis.
You have probably heard of some hunger hormones, including ghrelin, insulin, and leptin. I hope this posts gives you a deeper understanding of what they are and what they do in your body.
Please note that this post is not about reproductive health, nor directly about reproductive hormones. I will address how eating impacts reproductive hormones / health in an upcoming post about PCOS/HA, but I felt this post was useful to lay the groundwork for that future post, as well as other upcoming posts about starvation metabolism and keto-dieting.
I hope this post gives those who are curious a small glimpse into some of many biological factors at play that impact human hunger and satiety. I hear a lot of language that applauds ignoring these cues, which confuses me once you overriding your hunger and fullness cues longterm can cause you to feel really out of touch with what your body needs. But more on that in another post.
For now, let’s dive into hunger hormones 101:
*Disclaimer: As always, this is general information intended for healthy adults. Your needs may vary based on medical status, lifestyle, or life-stage. Please never replace generalized health information you’ve read online with individualized clinical care.
PS: If you are interested in reading about the difference between hunger and appetite and fullness vs satisfaction, click here.
This is known as the ‘hunger hormone.’ Ghrelin is released by cells in your stomach and intestine to stimulate appetite when calorie signals are low. The hypothalamus (a small region in your brain that is responsible for many homeostatic processes) contains a region ghrelin receptors to sense when levels increase.
Basically, ghrelin is your body’s way of saying “Hey! You up there! Feed me! I am hungry!” Your body needs food as fuel for everything you do, from walking to exercising to those important life-maintaining tasks such as breathing, pumping blood all throughout the body, digesting food, and maintaining normal brain function.
Therefore, when your ghrelin is high and your body is telling you to eat, I suggest you do so as to not override your body’s homeostatic functions!
As a meal is consumed and absorption begins, ghrelin secretion quickly declines. Your hypothalamus no longer gets a need-to-feed signal and your hunger decreases.
Ghrelin also plays other roles in your body, including decreasing the energy your body devotes to temperature regulation. That’s why you often hear of people who are undereating or dieting as constantly being cold.
Leptin is a hormone secreted by white adipose (fat) tissues. It is commonly thought of a the “fullness,” hormone, as it signals the hypothalamus to reduce hunger. Leptin levels are correlated with fat stores in the body; the more triacylglycerol a fat cell contains, the more leptin it produces.
As a person loses weight, the adipose (fat) tissue in their body decreases, as does their leptin levels, and hunger is not suppressed as much, meaning weight loss can indeed make an individual more hungry.
Likewise, if a person is under-eating or dieting, leptin levels decrease, meaning you may not feel full. This is your body’s survival mechanism against starvation.
Obese individuals may be resistant to leptin, making it hard for them to regulate their appetite. More research is needed in this area, but this concept is compelling in that it may help explain why it is so difficult for many to lose weight.
Adiponectin is a hormone that comes from adipose (fat) cells that also plays a role in homeostasis. Adiponectin in the blood stream decrease with weight gain and increase with weight loss. Animal research suggests it plays a role in insulin resistance.
Insulin is a peptide hormone made by beta cells in the pancreas. It controls the amount of glucose (sugar) in the blood and is considered the main anabolic (build-up/construction) hormone in the human body.
In addition to regulating blood glucose levels, insulin is thought to play a role in appetite regulation. Insulin stimulates the storage of triglycerides into adipose (fat) tissue. This stimulates the release of leptin, thus likely decreasing appetite, though more research is needed to fully edulidicate the precise biological mechanisms of leptin on appetite regulation.
CCK is a hormone produced in the small intestine. It is released rapidly after a meal. CCK also plays a role in satiety. It helps signal fullness, opposing the actions of ghrelin. CCK is thought to play a role in the regulation of digestion of fats and proteins.
Peptide YY (PYY):
PPY is secreted by the small intestine and the colon. PYY can suppress hunger for longer periods of time, up to 12 hours.Llevels are low in the fasting state and rapidly increase after eating. Baratric surgery has been observed to elevate PYY levels in individuals.
Glucocorticoids are steroid hormones that come from the adrenal glands and are involved in glucose metabolism. In a starved state, cortisol (a glucocorticoid) stimulates several processes to increase glucose levels in the blood in an attempt to maintain life, including stimulation of gluconeogenesis (breakdown) of the liver, breakdown of fatty tissues, among others.
I hope this post gives you a glimpse into some of the factors at play in regulating your hunger and fullness levels! As mentioned above, a post about hormonal health and nutrition is coming soon. However, I felt a quick post on this could be useful for reference and to give a knowledge base in preparation for the next post. Until then, enjoy!
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- Hunger vs Appetite, and Fullness vs Satisfaction
- How much fiber do I need? And how can I increase my intake?
- Celery Juice: What does the science say?