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Why do we get hungry: The Science Behind Eating?

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Why do we get hungry: The Science Behind Eating?

Our bodies are finely tuned machines and they need fuel to function. Cells present in our body need the energy to manufacture new proteins and to make chemical reactions function appropriately. So, we need to eat for our survival and to gain energy to function but, there’s some complex science behind eating. 

Now, you don’t just eat something because it tastes good or looks tempting. Your body is an amazing energy-generating machine. So, it’s constantly converting what you eat into energy even when you sleep and using this generated energy from the food for all sorts of tasks and activities that are done by you.  

Everything you do consumes your energy. You use about 75% of your energy from your meals and things like breathing, circulating blood, and growing. Then 10% of it is used simply to digest what you’ve just eaten. The remaining 15% is used up in the things that you choose to do, whether it’s walking in the park, or studying for an exam, or even watching T.V.  

But why do we feel the need to eat? Curious? Let’s find out. 

 To release chemical energy from your food, your body needs to combine your food with the oxygen from the air and it produces glucose in the blood which then turns into energy. 

Now, when we study eating or our body’s relationship with food, we look at the two aspects: 

  • When our body is compelling us to eat. 
  • When our body indicates that we are full 

Food intake and energy consumption must be balanced to maintain a healthy body weight. This balance is sustained by the central nervous system of our body which controls our eating habits and energy metabolism. 

It involves brain systems and hormones that are involved when we are about to eat or when we feel hungry. Hypothalamus is a chamber of our brain which consists of several small nuclei which pick up hormonal and nutritional signals from food circulation.  

This portion of the brain collects information about the body’s nutritional status, and responds accordingly. It also connects with reward and motivation channels, which influence our eating habits and food requirements.  

The Nutritional status of our body is categorised below:


Nutrition Status Action
Hunger Eating & Preserving Energy
Satiety Stop Eating, Spend Energy

 What is Satiety? 

Hunger can be triggered not just by our need for food, but even by the sight or the smell of it. There’s a biological reason why a person feels hungry—it is activated by a lack of glucose in the blood. 

The signal of reduction of glucose in the body is sent by a hormone called ghrelin that signals the brain to command the body to eat. There’s also a biological reason behind a person feeling full after eating—Scientists call them “satiety signals”.  

Satiety is the feeling that indicates the fullness that a person experiences after eating and suppresses the urge to eat more. The stomach expands to make room for the meal, causing satiety signals in the brain to go off. These hormonal signals trigger our body’s digestion process and absorption of nutrients.  

On the other hand, a hormone called ‘leptin’ provides information to the brain about nutrition and fat status of the body which means a person with more body fat will have less appetite causing him to eat less as compared to a thin person.  

Why do we overeat? 

  • Boredom: When we are bored, we are looking for some distraction and stimulation. Thus, increasing the release of our neurotransmitter (mood affecting chemicals) production which signals our body to feel ok. 
  • Fasting or long periods without eating: What happens when you’re busy working or fasting? You ‘Starve’ rather than feeling ‘hungry’. So, you tend to eat more than normal.  
  • Choosing a bigger plate: Choosing a bigger plate to eat may lead to an increase in food quantity and encourage you to eat more. Choosing a small plate for every meal could limit your food portion, restricting you to eat less.  
  • Emotional-Comfort Eating: Sometimes life can turn tough and stressful. Many people find something that could help them cope with this situation. For instance, you may think that a piece of chocolate cake can provide you comfort and make you feel better while you’re stressed but, that’s not the case. Your body is just producing neurotransmitter (mood affecting chemicals) production which signals your body to feel temporarily normal. 
  • People around you: food is something that brings people and the community together. When we eat, people around us can make us overconsume. People often say, ‘Have some more’ or ‘You barely ate!’ or ‘This is so yummy, you have to taste it!’.  

Key Takeaways 

By looking at the above factors, we can say that our brains have the power to control our hunger based on what we eat, deciding whether we are full or not, and the availability of extra calories.  

That’s all from us for today. Stay tuned to SpeEDLabs for more such amazing science stuff!


Also published on Medium.

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