# Why does it take 20 minutes for the brain to detect the stomach is full? **URL:** \ **Category:** Factual Questions\ **Created:** [July 4, 2001, 2:21am UTC](https://boards.straightdope.com/t/why-does-it-take-20-minutes-for-the-brain-to-detect-the-stomach-is-full/71160 "2001-07-04T02:21:54Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Sycorax](https://avatars.discourse-cdn.com/v4/letter/s/a4c791/32.png) [@Sycorax](https://boards.straightdope.com/u/Sycorax)\ **Post date:** [July 4, 2001, 2:21am UTC](https://boards.straightdope.com/t/why-does-it-take-20-minutes-for-the-brain-to-detect-the-stomach-is-full/71160/1 "2001-07-04T02:21:54Z")
Being on perpetual weight loss campaign, I’ve read many times (and just recently on a weight loss web site) that it takes the brain 20 minutes or so to register that you’re stomach is full. My own experiences bear this out – I’ll have dinner, then say, oh I’m not full, why not have that yummy, fattening dessert, and continue to pig out. But about l5 or 20 minutes later, I feel like I’m going to explode. Pleasure and pain are registered with the brain immediately; why does it take so much longer for the stomach to tell the brain “hey, I’m full, don’t let the piglet send any more food down here!” ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [July 4, 2001, 4:47am UTC](https://boards.straightdope.com/t/why-does-it-take-20-minutes-for-the-brain-to-detect-the-stomach-is-full/71160/2 "2001-07-04T04:47:05Z")
How full or empty the stomach is has nothing to do with whether you feel hungry or not. The feeling of hunger is caused by the level of sugar in the blood and other such things and is totally unrelated to whether there is anything in your stomach. Similarly, the feeling of thirst is not caused by any need to fill your stomach with water. if you start to dehydrate and feel very thirsty, you can drink half a gallon of water and feel it sloshing around inside your stomach, and yet you will still be thirsty for a while until the water gets in the bloodstream. You can fill your stomach with fiber and not feel very “full”. And you can eat much less volume of heavy, rich, fatty, greasy, food, and you will feel satiated for hours. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [July 4, 2001, 4:50am UTC](https://boards.straightdope.com/t/why-does-it-take-20-minutes-for-the-brain-to-detect-the-stomach-is-full/71160/3 "2001-07-04T04:50:21Z")
another theory is that the feeling of hunger is caused by vaginal dryness ---
**Author:** ![Mr.Cynical](https://avatars.discourse-cdn.com/v4/letter/m/ee59a6/32.png) [@Mr.Cynical](https://boards.straightdope.com/u/Mr.Cynical)\ **Post date:** [July 4, 2001, 4:59am UTC](https://boards.straightdope.com/t/why-does-it-take-20-minutes-for-the-brain-to-detect-the-stomach-is-full/71160/4 "2001-07-04T04:59:45Z")
Maybe that’s why I can’t tell. ---
**Author:** ![berdollos](https://avatars.discourse-cdn.com/v4/letter/b/ed8c4c/32.png) [@berdollos](https://boards.straightdope.com/u/berdollos)\ **Post date:** [July 4, 2001, 12:39pm UTC](https://boards.straightdope.com/t/why-does-it-take-20-minutes-for-the-brain-to-detect-the-stomach-is-full/71160/5 "2001-07-04T12:39:23Z")
you were full right away, you wouldn’t get enough food. ---
**Author:** ![Revtim](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/revtim/32/1042_2.png) [@Revtim](https://boards.straightdope.com/u/Revtim)\ **Post date:** [July 4, 2001, 1:20pm UTC](https://boards.straightdope.com/t/why-does-it-take-20-minutes-for-the-brain-to-detect-the-stomach-is-full/71160/6 "2001-07-04T13:20:52Z")
Or perhaps it’s something that evolved while calories were scarce. You come across a bunch of food, which is rare, so the body wants you to store as much as possible. ---
**Author:** ![Sycorax](https://avatars.discourse-cdn.com/v4/letter/s/a4c791/32.png) [@Sycorax](https://boards.straightdope.com/u/Sycorax)\ **Post date:** [July 11, 2001, 2:03am UTC](https://boards.straightdope.com/t/why-does-it-take-20-minutes-for-the-brain-to-detect-the-stomach-is-full/71160/7 "2001-07-11T02:03:30Z")
I see what you’re saying Sailor and it makes sense up to a point, but please elaborate: are you saying one doesn’t really “feel” full, or that the stomach doesn’t “feel”? If one eats or drinks something the stomach doesn’t like, the stomach protests and sends it back up right away, doesn’t it? (One experience comes to mind: I once ate one of those hot, green peppers and 15 seconds after it went down, I felt like I was going to throw up.) And why does my stomach “growl” when I’m hungry? Is that the brain telling my stomach to let me know I need food? Now that I think about it, what the heck is that growling anyway? ---
**Author:** ![domina](https://avatars.discourse-cdn.com/v4/letter/d/96bed5/32.png) [@domina](https://boards.straightdope.com/u/domina)\ **Post date:** [July 11, 2001, 3:04am UTC](https://boards.straightdope.com/t/why-does-it-take-20-minutes-for-the-brain-to-detect-the-stomach-is-full/71160/8 "2001-07-11T03:04:33Z")
There was a recent New Yorker article by Dr. Atul Gawande that dealt with this topic. > [@](#): > > When food enters your stomach and duodenum (the upper portion of your small intestine), it triggers stretch receptors, protein receptors, and fat receptors that signal the hypothalamus to induce satiety…(but) foods can trigger receptors in the mouth which get the hypothalamus to _accelerate_ our intake…A little bit on the tongue and the receptors push us to eat fast, before the gut signals shut us down…Apparently, how heavy one becomes is determined, in part, by how the hypothalamus and the brain stem adjudicate the conflicting signals from the mouth and gut. So apparently, your stomach can indeed “feel.” But it didn’t mention the 20-minute rule, I expect because there is no set time that it takes for all people to feel full. Gawande goes on to say that different people’s mouth-brain balances vary a lot, which makes some people more prone to obesity than others. ---
**Author:** ![Adithya](https://avatars.discourse-cdn.com/v4/letter/a/e99b99/32.png) [@Adithya](https://boards.straightdope.com/u/Adithya)\ **Post date:** [July 11, 2001, 11:13am UTC](https://boards.straightdope.com/t/why-does-it-take-20-minutes-for-the-brain-to-detect-the-stomach-is-full/71160/9 "2001-07-11T11:13:39Z")
The growling is the gastric fluids being secreted.The stomach says,“I want food now now NOW!”