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The Science Behind Hunger

The Science Behind Hunger

A few hours after a meal, we feel a desire to eat something again to fill our stomachs. That sensation inside your stomach is termed hunger.
Hunger is a complex sensation of feelings and activities inside our bodies. Every time you feel hungry, you need food to fuel your body with energy.
As simple as it sounds, hunger is more than just feeling hungry. There are certain hormones and a gut-brain connection that play a vital role.
This blog will help you learn about why and how we feel hungry.

Hunger and Appetite

We eat every day, from breakfast and lunch to dinner with some snacks in between. Sometimes we actually feel hungry and at other times we are just lured by a picture or a thought of food.

Hunger is a physiological process where a part of your brain (hypothalamus), glucose levels and certain hormones work together to produce sensations of hunger at regular intervals. At such times, your stomach growls and results in hunger pangs.

On the other hand, your appetite – a desire to eat, differs from hunger and can make you eat even when you are not hungry. This is triggered when you see or think of food and start craving a snack.

These facts sound interesting and there is a process behind them. So let’s understand the science behind hunger.

Why Do You Feel Hungry?

After a meal, a hormone called leptin signals your brain that the stomach is full and that you should stop eating. However, after an hour or so, you might start to feel hungry again.

Ever wondered why?

After a meal, your gastrointestinal tract gets empty by pushing the food towards the stomach and intestine. Simultaneously, gastric contractions, called migrating motor complex (MMC), clear up the undigested food in around two hours. The final contractions result from the action of a hormone called motilin, which results in hunger pangs.

The question arises: How do you know it’s time to eat as the signals are generated in the stomach but the brain commands us to eat?

This is where the gut-brain connection comes in.

Gut-Brain Connection: How do you feel hungry?

Interesting fact: Your brain and gut are connected through hundreds of nerves that help them to send and receive signals.

Through these connections, the nerves control several functions including appetite and satiety (feeling full).

The gut-brain connection can be felt when you feel angry or excited and feel butterflies in your stomach. This connection proves that the health of one affects the health of the other. The communication between the brain and the gut is called the gut-brain axis.3

One such nerve is the vagus nerve. It is one of the biggest nerves that communicates and sends signals. There have been several studies on humans and animals, that showed a strong connection between the vagus nerve and the gut.4

When your stomach is empty, the brain stimulates the hunger hormone ghrelin. It then activates expression neurons called agouti-related peptides (AgRP) in the hypothalamus area of the brain and tells us to eat something.

In other words, your brain can relate emptiness in the stomach when the vagus nerve sends signals from the gut. The brain then releases the hunger hormone and signal us to eat something. 1

In light of all of these science-based explanations, you might wonder why you still feel hungry and get drawn towards irresistible snacks between meals? Let’s learn some interesting facts.

Appealing snacks, Brain and Appetite

Haven’t we all drooled over pictures and videos of delicious-looking food at some time or the other? The bad part about this is that we get so drawn to food pictures and videos that sometimes we eat even when we are not hungry.

Why does this happen?

Let’s start with some basics. There are two types of hunger: homeostatic hunger and hedonic hunger. Homeostatic hunger is when your body is short of energy and feels hungry. Contrarily, during hedonic hunger, you are not truly hungry but you eat just to get extra energy.

When you see some snack, the brain gets notified and remembers what that snack or food item tastes like. As a result, your brain craves hedonic pleasure and it commands you to eat a snack.

It becomes irresistible for you not to eat that snack even after you are full or you don’t feel hungry. The excitement of having that bite dumbs down the feeling of fullness, makes you eat that snack and this results in binge eating.

This binge eating can cause weight gain, eventually leading to obesity.

When our lifestyles have become sedentary- and eating choices have drastically changed, there is an ongoing battle between what the brain tells you and what you should tell your brain.

The best solution to this problem is to choose healthy eating options. Between hunger, hormones and gut-brain connection, some of the eating control lies in your hand. While making healthy eating choices and indulging in physical activity, you can prevent some obesity causes.

If you have experienced significant weight gain, consult a specialist to get obesity treatment. You can also check out other blogs for obesity prevention sources.

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Reference Links:


  1. Blundell J et al. Appetite control: methodological aspects of evaluating foods. Obes Rev. 2010;11:251–270.
  2. Schwartz GJ. The role of gastrointestinal vagal afferents in the control of food intake: current prospects. Nutrition. 2000;6:866–873
  3. Carabotti, Marilia et al. “The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems.” Annals of gastroenterology vol. 28,2 (2015): 203-209.
  4. Pellissier S et al, Relationship between vagal tone, cortisol, TNF-alpha, epinephrine and negative affects in Crohn’s disease and irritable bowel syndrome. PLoS One. 2014 Sep 10;9(9):e105328.