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So, I recently learned about how exactly obesity is formed. I learned that if you consume too many calories but don't burn enough of them, your body will start to form fat. Then how come that people still get hungry even if they have plenty of engergy stored by fat?

In other words; Why does the body still need extra food even though it has plenty of energy?

  • Our body wasn’t developed for the abundance of food in nowadays society. Hunger is mostly measured as “how full the stomach is”, boldly ignoring (most) energy stored in fats. [That’s partly regulated by signals connected to glucose levels in the blood]. This Wikipedia article is a good starting point. Furthermore, Hunger also depends on psychological factors. – Narusan Nov 9 '17 at 15:57
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    There are incorrect assumptions. People don't eat just because of hunger. – Graham Chiu Nov 9 '17 at 18:26
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    This is actually a good question deserving a good answer. – Carey Gregory Nov 10 '17 at 3:09
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Hunger is far more complicated than "my weight is below normal for my height, I should eat now." It's not some sort of correction mechanism that turns on and off to make your weight go up and down.

On a first approximation, you feel hungry because your stomach is empty and/or your blood sugar is low. People can drink water or eat lettuce to fill up their stomachs, and that works a little. Often, if you eat something very high in sugar, not mediated by anything slower to digest, you will be even hungrier afterwards because of your body's insulin response. The web is full of "foods that make you hungry", "what to do instead of eating when you're hungry" and such like, some of which have a grain of truth in them, and that certainly demonstrate how complicated hunger is in humans.

Studies have been done showing that people can get hungry for a variety of reasons that have nothing to do with their current weight. Here's a review of various papers relating to insulin levels and cognitive factors such as looking at or thinking about food.

  • I get it now, of course energy isn't the only thing that your body gets from food. Thank you. – Jojo Nov 13 '17 at 20:54
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So think about fat stored in your body as being like money in a 401K.

You decide you need groceries, so you go to the store, but you can't use the money in the 401K to buy them, you need cash or a credit card.

Your body is the same; it needs immediate cash (carbohydrates/sugars...) for the day to day needs, and it tells you it needs them through hunger. Just like the 401K won't help you buy groceries, fat won't stop day to day hunger, so you have to eat.

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    While this serves as a very good analogy to the layperson, would you mind giving a more elaborate explanation for those with a limited understanding of the medical sciences, preferably including references? – Narusan Nov 12 '17 at 21:20

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