Why is your stomach growling right now?S

You're probably pretty hungry at the moment — which means your stomach is making a lot of noise. You hardly need an audio cue to let yourself know that you're hungry, so why do our bodies send us this alarm?

Image: Kate Ter Haar, on Flickr

If your family is like mine, you've skipped breakfast in order to, eventually, cram more food into your pie-hole. Depending on when you got up, and when you eventually eat, your stomach could sound like a bored cat rolling over, or a half-blocked storm drain during a rainstorm —okay or, if things are dire, like a demonically possessed wood-chipper. There are all kinds of audible variations, but why do we associate tummy-rumbling with extreme hunger?

When you look at the source of the stomach growls, it seems like we should associate it with fullness and contentment. After all, your gut does the majority of its work after you've stuffed it full of things to digest. Food moves through the body in a process called peristalsis. Muscles contract and force the food through the intestines like toothpaste through a tube. The food isn't a perfect consistency. Some things are liquid, some things are solid, and of course there is that perennial uninvited Thanksgiving guest, gas. The jostling of the three substances and the squishing of them through the intestines makes noise.

Why is your stomach growling right now?

Image: Stuart Spivack on Flickr.

But peristalsis doesn't always require food. When it comes to a choice between a little extra effort and death by starvation, the body chooses the effort. The body digests available and, in a few hours, expects to be fed again. And just to make sure it didn't miss anything, it will crank up the peristalsis. The feel of muscles contracting on an empty stomach is uncomfortable, so that's a motivator to go out and rip the second leg off the turkey. Also, the fact that we're paying attention to our stomachs probably contributes to how clearly we hear hungry stomach rumbles.

There's also another straight-forward explanation. The fuller a container is, the more muffled the noises. Fill a can with pennies and shake it, and you'll hear a quiet clanging. Toss a couple of pennies in on their own, and you'll wake the house. The more food you put into your stomach the more it muffles the other food you put in there. So eat, darling, eat!

[Via Scientific American, Discovery.]