After the turkey and the stuffing and the potatoes and the pie and the wine, it hits you: that overwhelming urge to put your feet up and snooze.
No, it’s not some lazy excuse to get out of doing the dishes, though that’s a perk. A new study in fruit flies suggests that it may actually be the salt and protein in a big meal ― as well as the quantity of food ― sending a direct signal to the brain that triggers post-feast sleepiness.
“Studies on the ‘food coma’ effect in humans have been hit or miss,” said study author William Ja, an associate professor at The Scripps Research Institute in Florida. “Sleep is really hard to study in people since very few can sleep ‘normally’ when they’re being watched.”
So instead, the researchers used fruit flies. Though the flies have very different sleep patterns than humans (they typically sleep in much smaller, more frequent periods throughout the day and night), the researchers were able to glean some insight into why we feel the urge for post-feast snoozing.
The brain may actually be wired for post-feast sleep
Feeding the fruit flies high-protein and large meals caused them to sleep up to twice as much in a 40-minute period after a meal as they typically would if they hadn’t eaten anything. And high-salt meals increased how much the fruit flies slept by nearly the same measure.
High-sugar meals, however, did not change the flies’ sleep patterns at all compared with their sleep patterns after not eating.
What’s more, the researchers found that specific brain circuits are actually involved in ― and likely cause ― the desire for post-feast naps, and are stronger or weaker at different times of the day. The food coma effect was not as strong for the fruit flies in the evening as in the morning, which suggests that the body’s circadian rhythm, or internal clock, also plays a role in when we are most likely to feel sleepy after a meal, Ja said.
“Maybe it’s good for digestion. Or maybe running around with a stomach full of food is just horribly damaging for your gut.”
This new fruit fly study is important, Ja added, because it opens up the door to more accurately study this phenomenon in living animals and better understand why it’s important.
“Maybe it’s good for digestion,” he said. “Or maybe running around with a stomach full of food is just horribly damaging for your gut.”
Previous research on people suggests that salt and protein may affect sleep hormones, Ja noted. But there has been little research to determine if these nutrients are specifically linked to food comas compared with other nutrients. He said those are questions for other studies in fruit flies and subsequently in people.
What you need to know to prepare for your Turkey Day meal this week: This study is more evidence that there’s a biological reason you feel ready to hit the couch after a holiday dinner ― especially if you loaded up on turkey.
Sarah DiGiulio is The Huffington Post’s sleep reporter. You can contact her at firstname.lastname@example.org.