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Why do we feel hungry after eating?

The feeling of hunger is our bodies' natural cue that we need to eat. This maybe because our stomach is empty or our energy levels are dropping. But, when we feel hungry, is that sensation always a true reflection of our bodies' needs?

We all start to feel hungry when our stomachs are empty. However, the sight of a tasty Christmas treat being shared in the office may tempt us and create a hunger feeling, even though we are not technically hungry yet. This happens because our brains are always on the lookout for energy-rich foods, just in case we need to go without later on. It is the brain that controls the sense and feeling of hunger through hormones.

After a meal, our digestive tract slowly empties by pushing food through the stomach and then the small and large intestines. Special contractions, called the migrating motor complex, sweep up undigested food (this process takes around 2 hours). The final process is regulated by a hormone called motilin. Motilin controls contractions that cause the rumbling in our stomachs and coincide with hunger sensations in our body.

Another hormone which causes hunger control is ghrelin. Research done on mice found that ghrelin activates neurons called agouti-related peptide, which tell us that we are hungry. These neurons are the control center for hunger. When these neurons are artificially switched on in the mice, they gorge themselves on food, regardless if they are full or not.

So, our brains pick up messages from our stomachs and tell us that it is time for our next meal, occurring around 2 hours after we have eaten. But, this does not explain the irresistible draw of a delicious snack between meals.

When our eyes detect something that we have previously enjoyed eating, our brain is notified. If we are full, we might refuse that snack or treat. However, our brains are hardwired to avoid running out of energy. The offer of extra food can therefore override our feeling of fullness and lead us to grab that tasty snack after all!

Simply put, our sense of hunger has not caught-up with the ease and regular availability of food. Thinking back to only 70 years ago, the country was still facing food rations after the effects of World War 2. Food was less available so people simply ate fewer calories. When there was extra portions or treats on offer, people would eat these without hesitation. Treats were simply that, a rare occasion where the body could grab some extra calories.

Availability of food is not only one of the modern day changes for our bodies. Even as recently as 40 years ago, most families did not own a car and relied on public transport and walking. These activities burnt more calories. Our desire to get eat extra calories, even when are full, would most certainly have been burnt off.

The human bodies' natural desires to find and consume extra food has simply not caught up with modern day society.

In the next blog, we shall explore further ways why we feel extra hungry and how this can be managed through diet.

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