Thanksgiving is practically synonymous with loved ones and giving thanks. But let’s be real: It also means plates piled high with food, a menagerie of desserts, flowing wine, and potential family drama.
For some, it’s the best time of the year. (Who doesn’t love a day of gluttonous eating with all of the people you love?) For others, the beginning of the holiday season marks the beginning of a time of pure stress — for body and mind.
After all, research suggests that the average American could chow down 4,500 calories during a typical Thanksgiving. And anxieties of the season (Aunt Carol needs to quit asking me why I don’t have a boyfriend…) can further that cycle, causing you to eat more than you would when you’re calm.
So what exactly is going on in your body as it’s overloaded with calories, alcohol, and conversation? Read on to find out.
Before Thanksgiving dinner even begins, there’s the anticipation of it all, says Josh Klapow, PhD, a clinical psychologist and associate professor at the University of Alabama at Birmingham. In other words, that’s when you’re thinking: “Oh, no, I don’t want to see my cousins” or “Ugh, is Dad going to get drunk?”
“Anticipatory emotions can very often set the tone of the dinner,” Klapow tells Yahoo Health. “We rarely go in with a blank slate.” Of course, what you’ll anticipate — and how you’ll react — differs from person to person. Some people will be happy; others, sad or remorseful. A third group may simply think, “Help! I don’t want to be here!” says Klapow.
“You may find yourself in all three buckets over the course of dinner — or just in one — and a lot of that drives your eating patterns,” he says. For example, you could get so caught up in conversation with an uncle that you end up not eating very much; on the other hand, you could use food as a way to check out of psychological distress, he explains. The same patterns can be said about booze. (More wine, anyone?)
Two, three, or four hours of this psychological marathon can build up and cause fatigue. “People’s emotional resiliency starts wearing down,” says Klapow. That could be why you find yourself on edge — or going from happy to sad every other minute. Complete overstimulation can lead to “emotional twitchiness,” Klapow says. “It’s not uncommon to hear that Thanksgiving was either amazing or horrific — it tends to bring out strong reactions, not neutral ones.”
As for once you start eating? Food impacts your brain too, especially as it’s flooded with amino acids from turkey, including tryptophan, says nutritional consultant Mike Roussell, PhD. But while tryptophan is often pinpointed as the cause of post-Thanksgiving-meal sleepiness, it’s actually not the biggest culprit. Instead, insulin released by the pancreas — thanks to all those excess carbs you’ve consumed — stimulates the production of serotonin, the “feel-good” hormone that can make you tired. So, really, it’s the insulin release that’s more likely the cause of your sleepiness post-meal.
Find yourself wanting to keep eating and eating even after you’re full? That may have to do with low levels of — or the overriding of signals of — a brain and intestinal hormone called GLP-1 that cues feelings of satiety, Kristin Kirkpatrick, RD, manager of nutrition services at the Cleveland Clinic Wellness Institute, tells Yahoo Health. Docs aren’t quite sure what causes low GLP-1 levels — or the signals to be overridden, for that matter — which can happen at any time. But here’s what they do know: “When the condition is reproduced in rat studies and the animals are driven to overeat, the rats overwhelmingly prefer high-fat foods,” Kirkpatrick says. (One way to prevent this may be to log zzz’s — evidence suggests that sleep deficiency can alter production of these hunger hormones.)
As your blood is flooded with sugar from your feast, your pancreas — which is responsible for getting sugar out of the blood — releases massive amounts of insulin to eat up the sugar, Roussell says. “However, due to excessively high blood sugar levels, your body overshoots the amount of insulin that it needs to release,” he says.
While amino acids enter the bloodstream — and are shuttled throughout your body to repair muscles and tissues — a spike in insulin can cause too much sugar to be pushed out of your bloodstream, leading to low blood sugar, says Roussell. This can make you feel tired. And because your body wants to bring your blood sugar back to balance, you could also be left craving, well, sugar, he says. And so the negative cycle continues.
Have a couple of glasses of wine, to boot? That’ll exacerbate the problem: Alcohol can also cause an excessive release of insulin and impair your body’s ability to recover from a low-sugar episode, Roussell says.
Once food hits your stomach, the digestion process begins with the help of enzymes, says Kirkpatrick. Carbohydrates such as vegetables and sweet potatoes are digested more slowly than regular potatoes or desserts because they are higher in fiber, she adds.
“As you eat, your stomach expands,” says Roussell. Normally, the stretch receptors in your stomach signal your brain that you have eaten enough and you feel full — but the desire to eat a lot at Thanksgiving can override these signals. Your stomach keeps stretching and you continue to eat. (Satiety signals are always there — you just have to choose to listen to them, he says.)
Fat cells and the lining of your stomach also secrete leptin and ghrelin, two hormones that regulate appetite, adds Kirkpatrick. “Leptin sends signals to your brain suppressing food intake, whereas ghrelin signals hunger and activates your brain’s inherent reward system, again perpetuating further consumption.”
“When you overeat, your heart has a lot to deal with,” says Roussell. Think about it this way: The food digestion process is supported by your parasympathetic nervous system — “the rest and digest” side of your nervous system, linked with relaxation and a reduced heart rate.
The problem? After you eat a big meal, your body makes digestion high-priority and calls for a lot of blood. “In order to get blood to your digestive system, your blood vessels dilate,” he says, noting that this can cause a drop in blood pressure. (This could lead to light-headedness, fatigue, and nausea.) Scientists call this postprandial hypotension (postprandial means “after eating”) — and the effect peaks 30 to 60 minutes after a meal, he says. So, instead of a reduced heart rate, you’re left with your heart working harder than normal to get blood to your digestive system and an increased heart rate. “For some people, this can be upward of 110 beats per minute, which is essentially low-intensity exercise!” Roussell says. You could feel your heart racing or even feel dizzy because of this.
Since wine — or any kind of alcohol — is a toxin, your body wants to get rid of it pronto, says Kirkpatrick. Sips of Sauvignon Blanc are rapidly absorbed into the bloodstream and then to the primary site of alcohol metabolism: your liver.
There, your liver converts alcohol from a noxious compound to an innocuous one, says Kirkpatrick. One problem: When alcohol is broken down, byproducts prevent it from properly breaking down carbs (ahem, like that stuffing), says Roussell. “So despite your body having ample carbohydrates (you just ate a ton), your liver essentially can’t access and use these carbohydrates. The alcohol also blocks your liver from breaking down and using fats,” he says.
And as for why you wind up drunk on Thanksgiving — even after chowing down? Your body can only process one drink an hour. “Any remaining alcohol continues to circulate in your blood — thus the genesis of the term blood alcohol concentration (BAC),” Kirkpatrick says.
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