You ever finish a large meal, but you’re still feeling hungry after eating?
How can that be? Your entire purpose of eating the meal was to not feel hungry.
Not feeling full is a real problem. Especially if you’re trying to eat healthier.
You’re either going to suffer through the hunger (which will ultimately lead you back to old habits). Or you’ll keep eating and end up consuming too much food.
Well you’re not alone, and you’re not crazy.
Glynn’s Guide: Takeaways That Won’t Fail You
- For overweight individuals, there is a decrease in leptin sensitivity. This results in an inability to detect being full.
- High carbohydrate meals increase serotonin output. This sends a message to our brain. This in turn increases our appetite for more carbs (or food in general).
- External cues can increase our appetite, but are perceived as hunger even when we are full.
- A sleep deficiency can increase hunger and appetite.
- Our metabolic set point may influence hunger if you’re losing weight. In other words, you may feel sated after a meal but your body wants more calories to reach its “old” goal.
A Professional Observation…
I constantly reenforce what you eat is more important than your workout to reach your fitness goals.
Over the years many clients have complained to me about feeling hungry after eating. In these cases, I’ve made several observations.
The three observations we’ll review that stand out the most are:
- Many people consume carbohydrates as a majority of their calories. They state they are still hungry after eating.
- Individuals who are overweight comment they’re sometimes still hungry after eating.
- Finally, individuals who eat more quality proteins and fats don’t make such comments.
Is this scientific research? No (but there’s a lot to be said for three decades of observing hundreds of cases).
So, I decided to dive back into this topic and first crack the textbooks. Then I looked over the more recent quality research to back up my observations.
There are some real connections between how our brain regulates hunger/satiety. As well as the behavior and feelings that these “signals” elicit.
There are many layers to understanding why you’re feeling hungry after eating. We will start with the complexity of communication in your central nervous system.
Let’s dig in…
Starting with the very important difference between satiety, hunger, and appetite.
What is satiety?
Satiety is a sensation that stops hunger. It’s the feeling we have when we’ve eaten enough.
You know it as a satisfaction that you’ve consumed enough food to not feel shaky, irritable or “hollow in your gut.”
Thus, if you’re still feeling hungry after eating, you are NOT satiated.
What is hunger?
Hunger is more specific than you think.
Hunger is a sensation that promotes hunger. It’s obviously the feeling we have when we need to eat. It is triggered by the hypothalamus as a means to regulate energy balance.
Okay, so what is appetite?
Appetite a learned response. It’s a desire to eat. We can experience an appetite without hunger and vice-versa. Sometimes appetite is the only contributing factor of feeling hungry after eating. To date, we still have more to learn about the chemical changes that influence appetite.
Appetite is typically a result of external factors and learned behavior, such as:
- Social pressure
- Celebrations (always seem to involve food)
We all know the perfect example when you’ve eaten a large celebration meal. You’re totally satiated and then dessert is presented.
Bam! Now you have an appetite again based on an external factor that caused an emotional desire. No doubt, you have all experienced this feeling. And you know how powerful it is over our behavior.
A brief recap of foods journey through the GI tract
Let’s take a journey from top to bottom through the gastrointestinal tract. It obviously begins in the:
- Mouth: chewing and initial enzymes for carbohydrate digestion introduced via saliva
- Esophagus: passage to stomach
- Stomach: Stomach acid denatures protein (breaks down by unraveling proteins). It also mixes and churns food into a liquid mass
- Small Intestine: Enzymes are secreted to digest all foods to nutrient particles. Cells in the walls absorb nutrients into the blood and lymph system.
- Large intestine: This is where water is reabsorbed as well as minerals. Bacteria use some of the nutrients to create nutrients essential to us.
- Rectum: Stores our waste until we’re ready and able to eliminate.
The following are important to mention:
- Liver: Produces bile, but has so many more important roles that we could do a whole other article on in the future. I believe it is the most important organ in the body.
- Gallbladder: stores our bile until it’s needed.
- Pancreas: Responsible for the production of insulin and enzymes for digestion. Also for the production of bicarbonate to neutralize stomach acid.
What hormones deliver the message?
The next few sections are where it gets fun if you dig physiology!
There are four very specific hormones that deliver a message to the hypothalamus. But this is only a glimpse into the complexities of the communications between the brain and the gut. We’re still learning.
Ghrelin is your hunger signal. It is a neuropeptide produced in the gastrointestinal tract. When the stomach is empty Ghrelin is released, promoting eating.
Leptin is made by white fat cells and circulates in the bloodstream. It reduces food intake. It binds to receptors which activate the medial hypothalamus (promotes satiety). This inhibits the lateral hypothalamus to suppress hunger. It is thought to be part of a negative feedback loop which helps with our long-term fat store “set point.” When fat increases, more leptin is released, suppressing eating. When fat stores drop, leptin levels drop. Thus reducing that feedback (which may indirectly promote eating).
Cholecystokinin (CCK) – As your gastric compartments fill CCK is released. This circulates in the bloodstream. It also stimulates vagal signals that go to the brainstem. Eating stops.
Insulin reduces food intake by binding to receptors in the medial hypothalamus. It functions similarly to leptin in suppressing eating behavior.
Ironically, in obese individuals, there’s a decrease in leptin sensitivity. This results in a mild inability to detect satiety. This may be one key factor contributing to being hungry after eating. Remember this part.
How is the brain involved?
The hypothalamus is a very important part of the brain (what part isn’t…) that regulates hunger.
In fact, it coordinates several systems into the appropriate behaviors. They are the endocrine, autonomicPart of the nervous system that we have no control over, i.e, it auto regulates. and somatic motor systemsPart of the nervous system that we have full control over, e.g., using your muscles to lift something..It’s located near the base of the brain (if you’re interested). And the part of the hypothalamus that we’re concerned with is the middle region.
It is in charge of some of the items listed below:
- Maintains homeostasis
- Regulates body temperature
- Helps regulate sleep
- Has a great deal of control of the GI tract
Stimulation of this part of the hypothalamus has a cool effect. It will cause in increased secretion of gastric juices and peristalsis. Peristalsis is the contraction of the muscles surrounding the GI tract. Bottom line, the middle region regulates our behaviors toward food acquisition. It also regulates the feeling of satiety, which is both perceptions.
The vagus nerve is the information highway between the gut and hypothalamus and sends the information to the medulla. Which in turn relays the information to the hypothalamus. Most importantly, the signals that regulate food intake are also responsible for the regulation of our energy balance.
In many studies, animals are given the freedom to eat whenever they like during experimentation. They still regulate their energy balance very well over a longer duration of time.
We are the same way (without outside influences). But the external influences are really strong!
What is the enteric nervous system?
This GI tract has its own “in-house” autonomic nervous system. It’s called the enteric nervous system. All we need to know is that it governs over functions of the GI tract.
One of my professors always called it our “second brain.” I’ve also heard it referred to as the “gut’s brain.”
What neurotransmitters influence our behavior toward food?
We already discussed that leptin, ghrelin, CCK, and insulin. They all play a role in delivering the message to the hypothalamus.
But what hormones affect the hypothalamus to in turn affect our behaviors?
- Serotonin: It is a neurotransmitter. Serotonin is produced in the brainstem and specific cells in the gut. It has an influence on the enteric nervous system that resides in the GI tract. It causes contraction of the smooth muscle around the stomach. We’ll discuss this one in more detail in a moment.
- Neuropeptide Y: It has an effect on the initiation of eating
- Cholecystokinin (CCK): has many roles, but one is to send a signal relaying fullness or satiety to the brain.
And down the rabbit hole, we go…. The are many neurotransmitters, hormones, and interactions involved. They all play an almost endless role in our hunger and satiation behavior. In other words, there’s a lot more.
I know this is getting complicated, so bear with me and we’ll start to tie it all together soon.
Do specific macronutrients have an effect on these neurotransmitters?
You bet they do, but the one I want to focus on is serotonin.
Consuming carbohydrates stimulates the release of serotonin, but protein does not elicit such a response.
As many of you know, serotonin was once touted as our “feel good” neurotransmitter. But that is now widely refuted in the neurophysiology world.
Many studies have shown that this increased release of serotonin from carbohydrate consumption increases one’s appetite for more carbohydrates. If you track your food intake, you know exactly the feeling I’m referring to for this circumstance.
In fact, one could think of carbohydrates as a drug that elicit a desire for more carbohydrates.
Now let’s say there is weight gain from excess food intake. This ultimately leads to a depressed sensitivity to leptin receptors.
Remember, leptin is the hormone that signals satiety. This should lead to a minimized feeling of satiety (you’re still feeling hungry)!
When does satiety occur?
Satiety (you feel full) occurs when CCK and leptin send a message. The message is to the hypothalamus that we have consumed enough energy to sustain life.
We’ve pointed out the effect of carbohydrates on serotonin. We also pointed out the desensitization of leptin receptors from carbohydrates. Now we can start to see that the feeling of satiety can more be overpowered by appetite.
What are “gastric juices” and what role do they play?
As we all know, gastric juices are acidic and corrosive. This is to digest protein.
Secretion of gastric juices is increased by many factors. Some relevant factors are listed below:
- Sight and thought of food
- Stomach distension
- Food chemicals like caffeine
Gastric juice secretion is inhibited by some of the following factors:
- Loss of appetite
- Emotional upset (fear, anxiety, etc.)
- Too much stomach acid
- Distension of the duodenum (first part of the intestine)
- Presence of partially digested food in the duodenum
So, can you have too much stomach acid under some circumstances? Sure.
But, it’s something we’re still learning about for so many physiological applications. There is evidence that bacteria have an effective influence over the hypothalamus. This happens by effecting some of our hormones and neurotransmitters in the enteric nervous system.
What about bacteria’s role?
Bacteria’s role in this whole process has real merit.
However, it’s something we’re still learning about for so many physiological applications. There is evidence that bacteria have an effective influence over the hypothalamus. This happens by effecting some of our hormones and neurotransmitters in the enteric nervous system.
Carabotti, et al stated
“This interaction between microbiota and GBA appears to be bidirectional, namely through signaling from gut-microbiota to brain and from brain to gut-microbiota by means of neural, endocrine, immune, and humoral links.”
This is very cool stuff!
Some CNS and GI tract disorders have been associated with disruption of the gut-brain axis and the microbiota.
But that is an article for another time.
What about sleep’s effect on feeling hungry?
I have to include this part since during previous literature reviews and this one.
I came across a lot of supporting studies of a scary finding. They correlate restrictions in sleep to an increased output of ghrelin (hunger neuropeptide). And also a reduction in leptin (satiety hormone).
In other words, not getting enough sleep CAN increase hunger and appetite.
Conclusion on Why You’re Feeling Hungry After Eating
So, we’ve discussed the signals that give us a feeling of hunger.
As well as satiation and their influence on our behaviors.
We’ve concluded that hunger and appetite are two different things. They can both influence feelings and behaviors.
So, if you are consuming a high carbohydrate meal and/or are mildly overweight. There will most likely be a perception or a “feeling” of being hungry after eating.
There’s also our metabolic set point. It is the contrast between short-term and long-term metabolic needs. If you’re losing weight you may feel sated after a meal but your body wants more calories to reach its “old” goal. This plays a larger role than we once thought.
Also, external stimuli may also be giving you the feeling that you’re still hungry after eating. But this is appetite, not hunger.
Consuming fewer carbs and more protein will lead to a stronger feeling of satiety. Minimizing the behavioral response to hunger and appetite.
To sum it up…
Causes of Still Feeling Hungry After Eating
If you’re overweight, feeling hungry after eating is often from a decreased sensitivity to leptin. Suppressing your ability to feel full.
If you’re eating a high carb diet then your serotonin level goes up. Creating an increased appetite for more carbs, rather than feeling full.
Other contributors include external cues increasing your appetite, sleep deficiency, and your metabolic set point. Reflect on your own lifestyle to identify which may be causing your issues.
Research and Resources on Feeling Hungry After Eating – (NERD STUFF)
Blundell, J.E.Hill, A.J., Serotoninergic modulation of the pattern of eating and the profile of hunger-satiety in humans, Food and Agriculture Organization of the United States, 1987.
Brodel, Per, The Central Nervous System, Structure and Function, New York, NY: Oxford University Press, 1992.
Caballero, B., Brain serotonin and carbohydrate craving in obesity, Food and Agriculture Organization of the United States, 1987.
David E. Cummings and Joost Overduin, Gastrointestinal regulation of food intake, The Journal of Clinical Investigation, January 2007. Pg 13-23
Karine Spiegel, PhD; Esra Tasali, MD; Plamen Penev, MD, PhD; Eve Van Cauter, PhD, Brief Communication: Sleep Curtailment in Healthy Young Men Is Associated with Decreased Leptin Levels, Elevated Ghrelin Levels, and Increased Hunger and Appetite, Annals of Internal Medicine, December 2004.
Marieb, Elaine, Human Anatomy and Physiology 3rd edition, Redwood City, CA; The Benjamin/Cummings Publishing Company, Inc, 1995
Marilia Carabotti,a Annunziata Scirocco,a Maria Antonietta Maselli,b and Carola Severia, The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems, Annals of Gastroenterology, 2015 Apr-Jun; 28(2): 203–209.
Paintal, A., A study of gastric stretch receptors. Their role in the peripheral mechanism of satiation of hunger and thirst, The Journal of Physiology, November 1954. Pg 255-270.
Raj K. Goyal, M.D., and Ikuo Hirano, M.D., The Enteric Nervous System, N Engl J Med 1996; 334:1106-1115 Wurtman, R. J., & Wurtman, J. J., Brain serotonin, carbohydrate‐craving, obesity and depression. Obesity Research, 3(Suppl 4), 1995. 477s–480s.