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Why do we feel hungry – Learn Biology

Why do we feel hungry


Why do we feel hungry, this is a real question. Hunger represents the physiological need to eat food. In fact we feel hungry means that the body needs to replace the energy it has used up in activity. For example, our cars stop working when they run out of petrol. Petrol gives cars the power to move. In the same way, human beings need energy to live.


Basal metabolic energy


We use energy even when we are fast asleep. Our brains and organs continue working even when we are asleep. And we need to keep our body running. The minimum energy we need is known as basal metabolic energy.


We wouldn’t able to live without any energy. And as our energy gets used up, we replenish it. One of the ways of replenishing energy is to eat food. Our bodies extract things like minerals and vitamins from food to provide us with energy.





Glucose is an important source of nutrition for many creatures. Our cells cause a chemical reaction between glucose and oxygen to extract energy and discharge carbon dioxide and water. In human beings, the starch found in rice and bread is converted into glucose. Glucose give us energy. A lot of glucose is found in the blood after a meal. However the brain needs a lot of glucose and your body uses glucose to move your muscles. That’s why the glucose in the blood gradually reduces. To replenish glucose in blood, the body sends a signal that tell us to eat soon and that’s when we feel hungry.


Neutral fat


The spare glucose is first stored as glycogen in our livers. But the liver can only store a certain amount, and extra glucose is stored as neutral fat in our bodies. Becoming fat or thin is because the neutral fat in our bodies increases or decreases. When we are playing, or even studying, we are using glucose. And so, our bodies will convert the neutral fat into energy. When neutral fat is converted into energy, it also produces something called free fatty acid. The release of this free fatty acid is what makes us feel hungry. And the amount of free fatty acid in the blood increases rapidly. At this time, we eat more than we need, our body produce too many free fatty acids.


Brain and Hungry




When the free fatty acid increases in the blood, a part of the brain senses it. The lower part of the thalamus is in the centre of the brain. It controls appetite, sleep, movement of heart, regulation of body temperature, etc. The amount of free fatty acid in the blood is recorded in the lower part of the thalamus of the brain, and monitored by the feeding centre. The brain is the control centre that manages the entire body. When the free fatty acid id increasing, feeding centre gives the command “Eat some food.” And this is when we feel hungry.


Why do we feel hungry even after eating


Once we eat food, our stomachs get full, the mechanism of sensing this is different. The lower part of the thalamus called ‘satiety centre’ monitors the amount of glucose in the blood and tells us when we have had enough. That is when we feel full. It takes time for the glucose in the blood to increase. It is different for people but it takes about 20 minutes. This is why if we eat in a hurry, we take in more food than needed, before our stomachs get a chance to tell us it’s full. And the extra food is stored as neutral fat.


Why does our stomach growl ?


When we are hungry, we start thinking about food. The brain tells the stomach that it will soon receive food. The stomach then starts working and the ‘growling’ that we can hear is the result of air being pushed through the stomach to make way for food.

Now you know why do we feel hungry. We feel hungry or full depending on the orders given by the feeding centre and the satiety centre. And our brain controls both.


Read : Why our blood is red

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Why our blood is red - Know more about our Blood

Why our blood is red – Know more about our Blood