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I've just returned from the cinema, where I ate a large popcorn and a large drink. This equated to about 1200 calories. I do not feel full at all. However, for lunch I had chicken, potatoes and vegetables, which equated to about 800 calories. Afterwards, I felt very full. I did not have breakfast this morning or snack during the day, nor did I exercise substantially during the day.

Why is it that food with more calories can seemingly make you feel less full than food with fewer calories?

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Satiety is not, and never was, a measure of the calories you have eaten. You feel sated when a certain type of neurons fire in your brain. These neurons are triggered by 1) impulses incoming from the enteric nerve network (motor neurons which partake in peristalsis) and 2) a number of hormones, including GLP1, orexins, cholestokynin and the leptin/ghrelin pair. It is however not yet entirely clear if we know all hormones involved, and what mechanisms determine the release of these hormones.

In two words, it is a very complex matter, and we don't know what exactly creates a feeling of hunger or satiety, but we know it's not something simple as the amount of calories, or the amount of food measured by weight, or the amount of food measured by volume.

Source: Kandel "Principles of neural science", plus a Coursera course on diabetes

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  • So basically you're saying that ingestion of different kinds of food causes the release of varying degrees of - or different - anorexigenic peptides which then signal satiety (in addition tovagal stimulation by mechanical and chemical receptors in the gut and environmental factors)? +1
    – anongoodnurse
    Commented Jan 13, 2016 at 5:08
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    @anongoodnurse Yes, I'm saying that. But I'm also saying that it's not very relevant. The point is, many people have a very wrong idea of the human body, thinking that the facets of our perception are a direct sensory measurement of some objective quality in the outer world - that vision is a simple translation of lightwaves the way a camera translates them, that the feeling of pain is a simple message of "tissue is damaged", that the feeling of hunger is a simple message of "not enough calories ingested". The question was obviously posted starting from such a wrong view. I tried to (cont.)
    – rumtscho
    Commented Jan 13, 2016 at 12:52
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    (cont.) convey that it is, as all other feelings, the output of a neural network working in the brain, and that none of the inputs has a deterministic connection to it. I also listed the main inputs which have already been found, and noted that the very simple "suspects" like calorie number only have a very indirect influence on the feeling. Of course, it's a very complex message to bring across in the short space, especially when I don't have all the exact mechanisms in my head.
    – rumtscho
    Commented Jan 13, 2016 at 12:55
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    It can also be affected in a somewhat psychological way. When you eat excessively oily food some people will immediately associate the oily feeling with fullness, and oiliness can also be unappetizing per se. It's a different story if you absorb the oil in something else. The point I want to make is that it also has a psychological aspect, not just physiological and neurological aspects.
    – busukxuan
    Commented Jan 17, 2016 at 22:09

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