Most of us are well used to the concept of binge-drinking and there's no greater time to go hard on the booze than during the festive season. 

With Christmas parties coming out of your ears all throughout December, a fair few drinks to wash down your turkey dinner on the day itself (plus all the alcohol you need to deal with the inevitable Christmas family drama) and then a night out on New Year's Eve all happening within quick succession, it's no wonder half the population decide they need to sort their lives out with a detox come January time.

But what is all that drinking really doing to your body? We all feel ropey with a hangover the night after a big one; but what actually happens when you consistently drink too much, often on consecutive nights?

We spoke to Consultant Hepatologist and liver expert Dr Alastair O'Brien from The London Clinic to find out, and I'm not suggesting you put down the bottle once and for all, but hearing what he has to say might make you think twice about having that extra G&T next time you're out.

Your appearance
Let's get the vanity part out the way, shall we? Because while boozing can be a lot of fun, it doesn't exactly do wonders for the way you look. 'Alcohol in large quantities has almost no benefit whatsoever,' says Dr O'Brien, pointing to people with pre-existing skin conditions as one reason why. 'People with skin diseases like Rhodesia or psoriasis will notice that they get worse after drinking. They will flare.'

And even if you don't have troubles with your skin, alcohol in large quantities can still impact the way you look. 'There are the simple things like not removing your makeup at night, or having an extra ten minutes sleep in the morning rather than having a shower,' notes the doctor. 'But also alcohol causes the blood vessels in your face to dilate upon the skin so you'll look red-faced and ruddy. It really isn't good for your appearance at all.'

Your weight
There's no beating around the bush: drinking alcohol in great quantities will make you put on weight. 'It's the hidden calories; if you drink enough it's equivalent intake of a takeaway pizza, but you still feel hungry,' points out the doctor.

And then what do we do? 'You feel hungry, you then go and eat something horrendous with a huge salt content because your judgment is weakened and your eating habits go out of the window. You're doubling your calorie consumption,' he says, quite rightly.

And when you then consider that you're probably too hungover to do anything to burn it off the next day, the scales are only going to go in one direction, and that's up.

Drinking on a hangover
Hair of the dog is that age-old hangover cure, and it often comes into its own at Christmas time when you've planned a night out after night out. But Dr O'Brien warns us against it.

'The hair of the dog will temporarily make you feel a bit better because some of the symptoms you are experiencing are a direct withdrawal effect. So the tremors, the sweats, they're an overactive sympathetic nervous system that will feel better if you have a small drink.'

But here are the downsides: you end up getting drunk quicker, and it just masks the hangover, it doesn't take it away.

'It takes us an hour to metabolise one unit of alcohol,' the doctor reminds us. So if you were drinking until 2 am and had along the lines of a bottle and a half of wine – roughly 15 units – that will take 15 hours to completely remove itself from your system. If you start drinking again the next day, your body hasn't even finished metabolising last night's alcohol before it can start on the new influx, so you get drunk quicker.

'Your body is feeling bad for a reason. Listen to your body,' says Dr O'Brien. Words of wisdom.
Your immune system
Hate getting colds? You might want to lay off the booze, then. 'We believe – although this has only been shown in experimental studies – that your immune function system is reduced [after drinking alcohol],' says the doctor.

'If I take out some white blood cells from you on a day you don't drink and some white blood cells from you on a day that you do drink, the latter set's function will be severely impaired. That increases the risk of infection,' he adds. 'You're much more likely to pick coughs and colds up.'

Your sleep
When was the last time you woke up after a big binge session and felt fresh as a daisy and not in the least bit tired? It's probably rarely happened to be honest. And that's because, as the doctor explains, alcohol upsets your REM (rapid eye movement) sleep.

'This is a phase of sleep which is important for your body to rest, so if you miss out on that, it can really impact you the next day.

'Even if you call it a night at 9 o'clock and go to bed you will not feel refreshed the next day if you had too much to drink the night before,' Dr O'Brien adds.

Your brain
They say you lose brain cells when drunk, and given some of the stupid decisions we make under the influence, it's easy to see why. But Dr O'Brien says there is actually some scientific proof in it.

Describing an experiment which looked into people who suffered chronic (long-term) alcohol over-consumption, the doctor explained that 'the cognition scores of people doing simple arithmetic or memory tests visibly decline over and above what's expected with age'.

'And it can even be the same for what we would consider fairly modest consumption of alcohol,' he said.

And if you want any further proof that alcohol is damaging your brain, just think about what happens when you have too much of it. 'Alcohol is a depressant and if you drink enough of it you will fall asleep and your brain won't work. If you drink enough of it, you'll forget what happened,' says Dr O'Brien. These aren't normal behaviours in a sober person.

In the long run, your liver
Although we think our livers are invincible, Dr O'Brien gives us a gentle reminder that they're not. 'Liver disease is the only common cause of death that is rising in the UK,' he told us. 'It's gone up 400% since 1970, whereas every other common cause of death has largely stayed the same or dropped a bit.'

For those who didn't ace a Biology A-Level (that's me included), our liver is responsible for breaking down everything we put in our body and removing the toxins. So that's anything from food, to drink, and even medicines. In turn, it then creates proteins to help us build muscle and cholesterol. 'It's a crucial role within the body,' Dr O'Brien comments, which is why the liver disease is so concerning.

Especially when the doctor describes sclerosis of the liver as 'like a cliff face' – because 'you can feel fine even with very advanced scarring and damage. There are plenty of people walking around who have no idea that they've got a lot of liver damage, and the symptoms you develop that would put you in the hospital are the very, very severe spectrum of this.

'So you can be feeling relatively okay – you might have noticed you're a bit slower but might have attributed that to something else – until all of a sudden you fall off that cliff; you go yellow, you vomit blood and if that doesn't kill you, certainly life will never be the same.'

So while we probably aren't anywhere near falling off the edge of that cliff face quite yet (and some of us never will) it's probably worth being mindful that too much alcohol could be pointing you in that direction.

So maybe you don't need that last round of shots on your next night out...