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Understanding the Science Behind Feeling Satiated: Mechanics and Physiology Explained

When Do We Feel Satiated

Have you ever wondered how you feel the sensation of being full? Most likely, you're thinking, "Of course, when my stomach feels full, then I'm full." 


Partially, that is true. However, science shows that there are significantly more mechanisms involved in our feeling of satiety, such as:


  • our thoughts & cognitive processes, e.g. what we think about the food

  • the presence of different flavors and textures

  • the composition of nutrients in our meal (carbs, fats and proteins)

  • the release of different hormones, especially leptin and ghrelin

There is a so-called satiety cascade. This helps us understand which mechanisms contribute to a longer-term feeling of satiety.


In this post, I want to explain to you the scientific findings regarding satiety, hunger, and appetite and what the difference between these is. I hope this post helps you to develop a better understanding of your feeling of satiety and gives you some 'aha-moments' when it comes to why you feel more or less full after certain meals. 


In-depth knowledge for your new & fit self.




hunger


The Difference Between Hunger and Appetite

Before we delve into explaining the satiety cascade, let me first explain the differences between hunger and appetite. These two terms generally describe certain bodily signals or sensations that we perceive, which control our food intake. Hunger and appetite lead to eating.


According to scientific definition, hunger and appetite are not synonyms!


Appetite

Appetite is more about the desire to eat a specific food without intense physical symptoms occurring. Appetite often focuses on a particular food item, such as chips or chocolate, etc. It can vary from person to person and can be influenced by factors such as culture, mood, stress, and past experiences with food.


Unlike hunger, which is a biological response to physiological need, appetite can be influenced by external factors and may not always reflect the body's actual nutritional requirements.


Appetite can also occur even though we have recently eaten and feel satiated.


Appetite is a psychological desire or craving for food influenced by various factors beyond physiological need.

Hunger

Hunger, on the other hand, is usually accompanied by an unpleasant, painful desire for food and is not always directed towards specific foods. Hunger can manifest physically through a rumbling stomach, dizziness, concentration problems, weakness, lightheadedness or an empty feeling in the stomach.


It's a physiological sensation that arises from the body's need for food and nutrients. It is controlled by complex physiological mechanisms involving hormones, neurotransmitters, and the nervous system.


Hunger is primarily regulated by hormones such as ghrelin (the hunger hormone) and leptin (the satiety hormone), as well as by blood sugar levels and stomach distension.


eating


How Does Satiety Occur?

Overall, there are 5 mechanisms involved in whether we feel a sense of satiety. These 5 mechanisms occur shortly or long-term after food intake. Additionally, there is a sixth mechanism, which is the learned mechanisms through our psychological experiences with specific foods and meals.


We will now examine each of the 6 mechanisms in detail. In the diagram below, you can see the order and duration in which the mechanisms take effect.


The Satiety Cascade



satiation cascade
satiation cascade


1. Sensory Perception

This includes the characteristics of your meal such as 

  • appearance

  • smell

  • taste

  • and texture. 

In German there is a saying that says: "We eat with our eyes". You've probably noticed that you eat more of a meal that is well-presented and meets your preferences compared to one that is perhaps uninspired and bland.


By the way: Our sensory perception is also responsible for the fact that after a main meal, even when we should feel full, we can still eat dessert. 


Crazy, no? That’s why we say “Dessert doesn’t go to the belly, it goes to the heart.”

Since desserts have completely different sensory characteristics (different texture, different flavor), we can still manage to eat it even though we couldn't eat any more of our main meal.


In practice, this means that you can consciously incorporate different flavors, textures, and smells into your meals. If you know you always crave something sweet after eating something savory, you can consciously eat a little less during the main meal to avoid overstretching your stomach.



2. Cognitive Perception & Beliefs

We all have certain opinions about food, such as "Carbohydrates in the evening are not good" (which is not true), or we estimate the calorie or fat content of foods. When you eat a meal that you know will satisfy you because it is rich and balanced, you will feel a stronger sense of satiety afterwards.


Compare this to eating just a salad, thinking it has fewer calories, even though it may actually have more calories due to its dressing or ingredients. 

In an experiment, it was shown that people felt fuller when they perceived the calorie amount of the meal to be high compared to when they perceived it to be low. Even though they didn’t know the exact calorie amount.


In practice, this means: 

  • you should question your beliefs about nutritional myths

  • educate yourself about what is actually true

  • generally aim for balanced, healthy foods that inherently satisfy you due to their fiber content



3. Post-ingestive Effects

Postingestive refers to everything related to effects within your stomach. These effects cannot be consciously controlled; they occur automatically after food intake.

 

For example, gastric distension, which we perceive as fullness, as well as the release of gastrointestinal satiety hormones in the stomach. Furthermore, the stimulation of chemoreceptors or chemosensors in the upper part of our small intestine plays a role.


In practice, you should aim to eat slowly, chew thoroughly, and occasionally put down your fork. Since postingestive effects take some time to kick in, eating more slowly helps you better perceive effects like gastric distension and avoid overeating.



4. Post-resorptive Effects

Postresorptive processes lead to satiety when all essential nutrients are present in your meal. Specifically, this means you should ensure that all macronutrients—carbohydrates, fats, and proteins—are integrated into each meal, and these nutrients should not be consumed in isolation from each other. For example, increased feelings of hunger may occur when your glycogen stores are depleted. You should then replenish these with complex carbohydrates to experience satiety.


The satiation effect of macronutrients can vary based on several factors, like individual metabolism, and eating habits. However, in general:


  1. Protein: Protein tends to have the highest satiation effect among the macronutrients. It can help you feel full and satisfied, potentially reducing overall calorie intake. Especially the amino acid tryptophan plays a crucial role in the central control of the brain. Tryptophan is found in nuts, grains, and legumes, among other foods.

  2. Fiber: Foods high in fiber, such as fruits, vegetables, and whole grains, also contribute to satiety. Fiber adds bulk to your meals, slows down digestion, and helps you feel fuller for longer.

  3. Fat: Fat is the most energy-dense macronutrient, providing more calories per gram compared to protein and carbohydrates. While fat can contribute to satiety, it's important to consume healthy fats in moderation as part of a balanced diet.

  4. Carbohydrates: The satiation effect of carbohydrates can vary depending on their type and how they are processed. Whole carbohydrates, such as those found in fruits, vegetables, and whole grains, tend to be more filling than refined carbohydrates like white bread and sugary snacks.


Did You Know: Potatoes have consistently been found to have one of the highest satiety indices among all foods tested.

The satiety index is a measure of how filling different foods are relative to a standard portion size. It quantifies how much a particular food satisfies hunger and keeps you feeling full after eating. The index is typically determined through controlled studies where participants consume standardized portions of various foods and report their feelings of hunger and fullness over a period of time.

The top five filling foods, based on their satiety index and nutrient content, are:

  1. Boiled Potatoes

  2. Oatmeal

  3. Eggs

  4. Legumes (Beans, Lentils, Chickpeas)

  5. Fish and Lean Meats



5. Hormonal Effects on Satiety

Hormonal changes play a significant role in regulating feelings of hunger and satiety. Two key hormones involved in this process are leptin and ghrelin.


Leptin

Leptin is often referred to as the "satiety hormone" because it is primarily produced by fat cells and signals to the brain that you have enough energy stored and are satiated.


When the number on fat cells increases due to higher energy intake, they release more leptin into the bloodstream. This rise in leptin levels communicates to the brain that energy stores are sufficient, leading to decreased appetite and sometimes increased energy expenditure.


However, in conditions of obesity, individuals can develop leptin resistance, where the brain becomes less responsive to the hormone's signals. This can lead to increased appetite and difficulty in regulating body weight.


Ghrelin

Ghrelin on the other side is often called the "hunger hormone" because it is primarily produced by the stomach and stimulates appetite. Ghrelin levels typically rise before meals and decrease after eating. This increase in ghrelin signals hunger to the brain, motivating to eat something.


Ghrelin levels are also influenced by various factors such as meal timing, nutrient composition, and stress. For example, skipping meals or restricting calorie intake can lead to an increase in ghrelin levels, promoting hunger.


Ghrelin also plays a role in regulating energy balance and body weight, and its dysregulation has been implicated in conditions such as obesity and eating disorders.



The interaction between leptin and ghrelin, along with other hormones and neurotransmitters, forms a complex regulatory system known as the appetite control network.

This network involves communication between the brain and various organs to coordinate energy intake and expenditure.


Overall, hormonal changes, particularly involving leptin and ghrelin, play a crucial role in signaling hunger and satiety, influencing food intake, energy balance, and body weight regulation.



6. Learned Mechanisms

This final mechanism, which plays a significant role in our perception of satiety, differs significantly from all other 5 mechanisms. 


It is believed that learned responses can overshadow all other mechanisms, and it may be that the natural perception of postingestive, postresorptive, cognitive, and sensory effects is limited because learned effects can be so strong and intense. These learned responses arise from classical conditioning and experiences from our past. 


For example, we have learned which texture or flavor subjectively satisfies us more. It may even be that through many fasting or hunger regimens, we have unlearned to listen to our hunger signals, such as stomach cramps, and it may result in us ignoring these bodily signals.


Conversely, we may not perceive extreme gastric distension anymore because we constantly overeat. This leads to the stomach continuously expanding, allowing us to consume larger meals without feeling full, which will likely lead to obesity in the long run.


In practice, this means that hunger and satiety signals are partly conditioned or learned, and it is important that we question, analyze, and be mindful of our eating behavior.


We should learn to better perceive, interpret, and understand our body signals rather than working against them.

The processes mentioned above partially overlap in their effects and should never be viewed in isolation from each other.


satiation cascade

Satiety is a psychophysiological process.

As you can see, the satiety mechanism is a highly complex process, and we should free ourselves from wanting to control everything.


Some things, like hormone secretion, are beyond our control. But we should utilize the aspects we can influence to develop a healthy hunger and satiety feeling in the long term.



Achieve your fitness goals now through personalized guidance from your online nutritional and fitness coach. Book a call now!




Yours,

Vanessa gaber signature




 


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