Nutrition plays a big role in our lives at this time of year.
But what happens when we go a little too far?
It's pretty safe to predict how you'll feel after a regular meal: sleepy, sluggish, and definitely full.
But at lunch time the next day, there will surely be room for another portion of roast.
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When you think about it, it's quite unusual that just a day after a huge meal we can eat exactly the same amount of food again.
Didn't we learn our lesson the first time?
Why do we still feel hungry after feasts like Christmas?
Does overeating "expand" our stomach, meaning you have more room for food the next day?
I'm getting hungry just thinking about it.
The answer, for most people, is that you don't feel hungry despite the massive amounts of food you've recently ingested.
You feel hungry precisely because of them.
But first, what is the feeling of hunger anyway?
The urge you feel to eat is the result of physiological changes in your body.
It is true that the size of your stomach changes when it is hungry or full.
The stomach shrinks as the meal is digested to help move the food towards the intestines.
Our stomach growls as air and food move around and food is pushed down.
It is a phenomenon called borborygmus, a sound and physical sensation, which is often our first hint that we might be hungry.
After emptying, the stomach then expands again in preparation for feeding - this is triggered by hormones.
But it is not actually true that feeding expands the stomach.
The stomach is very elastic, so it will return to its normal capacity (about 1-2 liters) after a large meal.
Moreover, most people's stomach capacity is very similar - neither height nor weight plays a role.
What we may not be aware of is the secretion of our hunger hormones: NPY and AgRP from the hypothalamus, and ghrelin from the stomach.
Ghrelin is secreted when the stomach stimulates the production of NPY and AgRP in our brain.
These two hormones are responsible for creating a feeling of hunger by overriding the hormones that make us feel full.
Probably counter intuitively, the level of ghrelin is usually higher in leaner people and lower in obese people.
You'd expect the hunger-stimulating hormone to be more present in people who eat more - but this contradiction probably reflects how complicated our endocrine system is.
And while only three hormones are mainly responsible for arousing the feeling of hunger, a dozen or more are needed to make us feel full.
A pair of them, GIP and GLP-1, are responsible for stimulating insulin production to regulate carbohydrate metabolism.
Several other hormones are involved in slowing down the movement of food through our stomach, so that our body gets enough time to digest the food.
In some obese people, it is possible that high levels of insulin, needed to metabolize a carbohydrate-rich diet, inhibit ghrelin production.
Two hormones are key to reducing the feeling of hunger: CKK and PYY.
This leads to loss of appetite.
Although your stomach has a hormonal system that tells your brain when it's empty, this is often reinforced by an acquired connection between the time of day and the feeling of hunger.
So even if you had a big lunch, you might still feel hungry at dinner time.
"If you persistently grab a piece of chocolate or chips after dinner when you sit on the couch to watch TV, our body can start to associate sitting on the couch, the TV, and eating something nice, so when you sit on the couch, you start to crave food," he says. Karolien Van den Acker, researcher from the institute Center data and once from the University of Maastricht.
"It can happen even when you're full; when your energy stores are full."
Overeating is not bad in itself, says Van den Acker.
Unlike the clinical diagnosis of binge eating, when very large amounts of food are ingested in a short period of time, often associated with feelings of disgust, guilt or shame, ordinary overeating can simply be experienced as a habit that people would like to break.
But acquired food cravings can also make successful dieting difficult.
When we learn to associate the rewarding properties of food, especially food with a lot of sugar, with specific times, smells, sights and customs, when you start to feel a craving, the memory of those sensations is activated.
This then triggers not only psychological but also physiological reactions, such as salivation.
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You've probably heard of Pavlov's dog - an experiment in which a bell was rung every meal time so that the dog would associate it with getting food.
Eventually the dog started salivating just at the sound of the bell.
Humans are not much more sophisticated than dogs in this regard.
In another experiment, people were shown simple shapes - circles and squares.
When they saw the squares, they got a piece of chocolate and after that they started craving chocolate every time they were shown the squares again.
Like dogs, humans can be conditioned to expect food based on simple cues.
"These bonds form quickly and even with a small amount of chocolate such as one to two grams," says Van Der Acker.
"It seems quite easy to arouse these cravings, but it is very difficult to get rid of them. Your body remembers that you ate chocolate at a certain moment.
"That craving can easily turn into a daily craving - even after only four days of repetition."
Sometimes even our mood can become a trigger for conditioning.
People often report having less self-control if they are moody or tired.
"In that case, the emotions can be directly linked to the tasty food, so then the bad emotion can trigger the craving," says Van der Acker.
In principle, any mood, even a positive one, can become a trigger for cravings, as long as it is consistently accompanied by food.
It has been proven many times that we eat more when we are in the company of friends.
Even after controlling for alcohol, special occasions, length of time you spend at the table, and many other factors, we still eat more when we socialize.
Perhaps it's because the pleasure that company brings makes it difficult for us to concentrate on portion control.
Even people in a lab eating a bowl of pasta will eat more if they have a friend to talk to.
This finding has implications for breaking bad eating habits.
"When we try to help people eat less, we focus on 'breaking' their acquired cravings for food.
"We try to teach them that eating something nice once doesn't automatically mean they have to do it the next day," says Van den Acker.
This is important because other studies have shown that giving up a good eating habit once can be enough to return to a bad habit.
Perhaps it's no surprise, then, how hungry we feel after a hearty meal with family and friends.
We're still hungry the next day - or even later that day - not because our stomachs have expanded, but because we've become accustomed to overeating on special occasions.
If our brain sees all the cues - smells, sights, sounds - associated with large meals the day after a big feast like Christmas, then it will start preparing us for round two.
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