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Why we always overdo Thanksgiving dinner: Scientists reveal what happens to our bodies when we overeat

When peptide tyrosine starts working, we get the sensation of being full
However, this takes 30 minutes to take effect we causes people to overeat
Previous study found that eating too much fatty food can damage nerves in the stomach that tell the brain we are full

By Ellie Zolfagharifard and Jonathan O'callaghan For Dailymail.com

Published: 15:31 EST, 23 November 2015 | Updated: 19:52 EST, 23 November 2015

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If there's one thing we're guaranteed to do on Thanksgiving, it's overeat.

Scientists believe it takes roughly 30 minutes for our brain to catch up with our bodies when we're eating.

It's during this period that we don't know whether we're full or hungry - and with so much good food on the table, it can be difficult to hold back.

If there's one thing we're guaranteed to do on Thanksgiving, it's overeat. Scientists believe it takes roughly 30 minutes for our brain to catch up with our bodies when we're eating. It's during this period we don't know whether we're full or hungry - and with so much good food on the table, it can be difficult to hold back

'The act of digestion is not something that just magically happens - it's a process that our body has to make happen,' Drew Hays, a registered dietician and a lecturer in the Department of Nutritional Sciences at the University of Texas, Austin, told Inverse.

3,000 CALORIES IN ONE MEAL

The average adult consumes 3,000 calories and 229 grams of fat in one Thanksgiving meal.

A 160-pound person would have to run at a moderate pace for four hours, swim for five hours or walk 30 miles to burn off those calories.

'But that sensation - feeling just so full - it's not only your stomach expanding.

'There are hormones that are released that tell us, 'Hey you've had plenty, time to quit eating.'

Leptin is a hormone and neurotransmitter that tells our brains when we've had enough to eat.

But when people eat too fast for him, or just ignore that hormone all together, another hormone, peptide tyrosine-tyrosine tells the brain that the body feels sick and bloated.

For some, come Thanksgiving, there's simply too much delicious food available for any notice to be given to this hormone.

And instead, they'll be left to deal with the biological repercussions of over-eating.

Hayes says we need to learn to control of food intake long before this hormone gets to work, perhaps by eating slower.

Scientists point out that there is some evidence overeating could cause permanent damage.

A study in June found eating too much fatty food can damage nerves in the stomach that tell the brain we are full.

An unhealthy diet can alter the balance of bacteria in the gut – encouraging those that thrive on fat to multiply and killing off others which prefer healthier food.

For some, come Thanksgiving, there's simply too much delicious food available for any notice to be given to this hormone. And instead, they'll be left to deal with the biological repercussions of over-eating

This can lead to inflammation of the nerves so the brain no longer senses signals telling us we have eaten enough.

US scientists said their research on rats found higher-fat diets altered the animals’ brains.

Krzystof Czaja at the University of Georgia said: ‘When we switch the rats to a high-fat diet, it reorganises brain circuits.

'It induces inflammation in the brain regions responsible for feeding behaviour.

'Those reorganised circuits and inflammation may alter satiety signalling.’

He said this change can lead to ‘gut-brain miscommunication’ – such as thinking we are still hungry even though we have eaten plenty.'

Last year a video that explained the science behind feeling full at Thanksgiving.

The video was created by the American Chemical Society's YouTube channel Reactions.

They explain that, when you eat a big meal, part of the reason you can feel full is down to the size of your stomach.

'Your stomach can stretch the volume of about one litre; that's about the size of a burrito,' the narrator says.

'When you eat a big meal you fill your stomach to its limits, squeezing against your other organs and making your abdomen feel, well, full.'

When eating your stomach and intestines also fill with gases, not only from food and drink but also gulps of air when you swallow anything.

IS THE URGE TO EAT TOO MUCH DOWN TO HORMONES?

In 2012, Robert Lustig, a professor of clinical paediatrics at the University of California, explained a new scientific theory on why people eat too much.

He argues that the urge to overeat and lounge around doing nothing is not a sign of weakness.

It is, he says, a hormonal issue, triggered by eating too much sugar.

He points the finger of blame at the hormone leptin, which acts like an appetite thermostat.

As one of two 'hunger hormones' in the body, leptin works to decrease the appetite (its partner, ghrelin, increases appetite).

When you have had enough to eat, your fat cells release leptin, which effectively dulls the appetite by instructing the brain that it's time to stop eating.

But Professor Lustig warns that our sweet tooth can send this process haywire and, if you are leptin-resistant, food never stops tasting delicious, no matter how much of it you choose to eat.

This additional air adds to the swollen sensation you get after eating.

Fizzy drinks can make you feel especially full, as the gas that makes them fizzy - namely carbon dioxide - can fill more space than the liquid it came in.

Your body can get rid of this gas though - in the form of burps and other methods that don't need to be explained.

'For some people another uncomfortable result of a big meal is heartburn,' the video continues.

'The stomach produces hydrochloric acid to break down food. More food to break down means more acid, which can creep into the oesophagus, leading to that burning feeling.'

Antacid tablets can alleviate this pain using bases, which are at the opposite end of the pH scale, to neutralise the acids.

Doing this, however, can release more carbon dioxide and increase the feeling of being full.

A video last year revealed how what we drink affects us - and how carbon dioxide in fizzy drinks can be behind the overwhelming urge to belch at the dinner table