The greatest love story of my life has been with a carbonated beverage.

I can’t remember a time when I wasn’t addicted to Diet Coke. Some memories: I am sitting at the kitchen table at my grandmother’s house in northern Cyprus, screaming because my mother won’t refill my yellow-and-green patterned glass. I am four or five years old. My grandmother looks on, disturbed, as I wail disconsolately. My mother does not give in.

I am a teenage anorexic. After a long day starving myself, I walk to the corner shop and reward myself with a bottle of Diet Coke. (My mum won’t buy it for the house any more, because of my addiction.) My low blood sugar makes the artificial sweetness taste euphoric.

It is my 30th birthday. I am at work at my former employer. To much fanfare, my boss brings in an eight-pack of Diet Coke, with a burning candle stuck in it. I am delighted.

***

I drink Diet Coke from the moment I wake up until I go to sleep. Five cans on a good day, seven cans on a bad day. My boyfriend jokes about my morning routine: wake up, pad to the kitchen. The sound of a can cracking; a hiss. Glug glug glug. Yes, every morning.

Using some back-of-a-fag-packet-maths, I estimate that I have drunk 11,315 litres of Diet Coke in my 31 years on this Earth. (I have been conservative with these numbers – it is almost certainly more.) That is more than 11,000 litres of caramel fizz, fermenting my insides, bathing my liver in foam.

I really want to stop drinking Diet Coke – and not only because I spend at least £500 a year on the stuff. It is embarrassing and bad for me. When I go on holiday, I fill up the supermarket trolley with Diet Coke, to the amusement of my friends. I get anxious if I don’t have any Diet Coke in the fridge as bedtime approaches; I run to the shop in the middle of the night to ensure there is a cold can waiting for me in the morning. I recently spent a year on prescription medication for a stomach condition that was almost certainly triggered by my overconsumption of Diet Coke, according to my GP. If enduring an endoscopy won’t stop you drinking fizzy drinks, you know you are addicted.

To keep the costs down, I buy 24-can crates from my local supermarket. The staff know me there and remind me if I forget to pick up a crate. This is mortifying, but helpful.

I want to quit. I have to quit. I quit smoking in my 20s on my first attempt, but Diet Coke is my aluminium Annapurna: I daren’t even attempt the summit. So I pitched this feature – mostly as a way of holding myself accountable – and set myself a target. By the end of January 2021, I would be Coke-free. If I am being honest with you, I didn’t think I could do it myself.

***

My attempt to quit Diet Coke does not start well. I finish my stockpile on New Year’s Eve, suckling from a two-litre bottle like a baby drinking from the teat.

On New Year’s Day, I wake up hungover and watch TV in bed with my boyfriend. We order pizza. “Add a can of Diet Coke,” I instruct him. “I thought you were quitting?” he replies. My head is pounding; only the caramel smack of Diet Coke will do. “Order it,” I say, my tone leaving no room for discussion. When it arrives, I down it, making little whimpering noises of pleasure.

The following day is worse. I find myself craving Diet Coke in a way that is alarming and unexpected. I envisage a tiny part of my brain – roughly parallel with my tongue and upper palate – that won’t become activated unless I drink Diet Coke. I want to dump a bucket of Diet Coke on this spot and watch it fizz. I know that my headache won’t go away otherwise. I feel horrific.

This – according to Dr Sally Marlow of King’s College London, a specialist in addiction and mental health – is because I am in physical withdrawal from the caffeine in Diet Coke. The average can of Diet Coke contains 42mg of caffeine, the equivalent of roughly two-thirds of a shot of espresso. Caffeine is a medically recognised addictive substance that, when taken in excess, activates the brain’s reward circuitry. “The caffeine will be stimulating neurotransmitter pathways, including dopamine,” says Marlow. “Your brain has become used to having a certain amount of caffeine in it and, when you take that away, you go through withdrawal. It’s physical. You get crashing headaches.”

Marlow confesses something unexpected: like me, she is a Diet Coke addict. “I managed to stop drinking it four years ago, but had to go cold turkey,” she says. “I don’t think it’s an option for me to have an occasional Diet Coke – it would rapidly escalate to five or six cans a day.” It took her four attempts to kick the habit.

It is validating to hear an expert tell me that my Diet Coke addiction is just that, rather than a bad habit. “Oh, it’s real,” Marlow laughs. She explains that addiction has a biological component and a psychological component. The biological component is your body’s physiological craving for an addictive substance, such as caffeine, nicotine or alcohol. “The minute you get that substance into your body, your brain knows about it and gets a hit from it,” she says. “Over time, you develop a tolerance for the substance.”

Marlow speculates that the bubbles in Diet Coke may increase the addictiveness of the drink. “This is only a theory, but we know that, when a person drinks champagne, they absorb the alcohol faster than if it were a glass of wine, because the bubbles increase the area that delivers alcohol into the bloodstream,” she says. “I wonder whether the bubbles in Diet Coke make you absorb the addictive substances in the drink faster.”

In a statement on its website, Coca-Cola denies that its products are addictive. “Many people enjoy sweet tastes from time to time, and that’s normal … Regularly consuming food and drink that taste good and that you enjoy is not the same as being addicted to them … Caffeine is a mild stimulant, and if you have it regularly and then stop abruptly, you may experience some headaches or other minor effects. But most of us can reduce or eliminate caffeine from our diets without serious problems.”

Then there is the psychological pull of a can of Diet Coke, something Marlow knows first-hand. “I would crack a can open and it was almost like Pavlov’s dog,” she says. “I’d anticipate having the Coke in my mouth. That’s the psychological aspect of the addiction.” She tells me that it takes 17 days to begin to kick an addiction. “The first few days are very intense,” she says. “Hang in there.”

I don’t have the fortitude to do as she did – go cold turkey – so I improvise an extraction plan. I will taper myself off Diet Coke: two cans a day for the first week, reducing to one can a day for the second week and no cans thereafter. I run to the shop and purchase an eight-pack. My mouth is watering as I carry it home.

***

How did I get to the point where I found myself umbilically attached to a sugar-free carbonated drink?

Like many women, I was cruel to myself in my teens. I grew up in the 00s, when the body-positivity movement was nonexistent. Rachel Zoe’s tribe of identikit US size zero (UK size four) waifs stalked the pages of every fashion magazine. Models spoke about subsisting on cigarettes and Diet Coke. “Nothing tastes as good as skinny feels,” said Kate Moss in 2009. I internalised that message wholeheartedly.

Every girl at my school aspired to be as thin as possible. The toilets smelled of vomit. At lunch, groups of dieting girls – myself included – would walk arm in arm to the corner shop, skipping food to buy Diet Coke, which filled you up and had zero calories. Diet Coke denoted thinness and social cachet. We all wanted a taste.

Over time, I flirted with other soft drinks – Pepsi Max is a favourite, because it is slightly sweeter than Diet Coke – but I always found myself returning to my original love.

Diet Coke was launched in 1982, seven years before I was born. I grew up watching the Diet Coke Break adverts, featuring a group of businesswomen ogling a topless hunk. The Coca-Cola Company already had a diet drink – Tab – but Diet Coke was marketed more smartly. “It has been a spectacular success since its launch,” says Prof Robert Crawford, a marketing expert at RMIT University in Melbourne and the co-editor of Decoding Coca-Cola. “It tapped into the zeitgeist of its time, which was professional women making their way in the workplace, looking good and feeling good. It also reflects the fitness craze of the period.”

In the 00s and 10s, Diet Coke leaned heavily into its association with the fashion world, recruiting Jean Paul Gaultier and Karl Lagerfeld as creative directors. More recently, as the body-positivity movement has gained traction, Diet Coke has pivoted away from this association. But as someone who grew up associating Diet Coke with skinny models, the imprint remains. To me, Diet Coke is diet culture in a can.

***

“I don’t want to make you beat yourself up even more,” says Aisling Pigott of the British Dietetics Association, when I ask her to tell me why drinking so much diet soda is bad for me. I can take it, I say. She relents.

“It will cause tooth erosion and lead to fillings,” says Pigott. My stomach will also be taking a battering, as I know from personal experience. “You’re at increased risk of gut ulcers, as well as irritable bowel syndrome,” she says. “And there are links between carbonated drinks and reduced bone density, meaning you’re more at risk of getting fractures as you get older.”

Although I was concerned about the health risks of aspartame, the sweetener in Diet Coke, Pigott tells me not to worry. “Aspartame is a heavily tested sweetener,” she says. “There is no strong evidence linking it to any health consequences.” In the grand scheme of things, Pigott says, Diet Coke isn’t terrible. “It’s definitely a better option than full-sugar Coke. But it’s the amount you’re having that is potentially harmful,” she says.

The first week of my regime passes without incident. I join a Facebook support group for Diet Coke addicts who want to quit. It may just be my caffeine withdrawal fug, but I find the positivity I am receiving from strangers online so moving that I am close to tears.

“If I can do it, anyone can,” one recovering addict says. “You’ve got this!” Another tells me she had to get colitis to quit. “The hardest part is that it calls me,” she writes. “I will never be free of that ‘Mmm, Diet Coke’ feeling. I love it.”

“Me too, buddy,” I think, upending a can to shake the last few drops into my mouth. “Me too.”

***

Week two of my tapered extraction programme. The first day is OK, but on day two I snap and drink four cans. I hide the cans in the bottom of the recycling bin, hoping my boyfriend won’t notice, but he had counted the cans in the fridge that morning. Rumbled.

It is humiliating, but the accountability helps keep me in check. I stick to one can a day after that, but only by drinking more tea than I have drunk in my life. I wonder if I will get to the point where I like the taste of water.

According to Anna Jezuita, a specialist change counsellor, I’m being hard on myself. “Diet Coke has been your friend since you were four,” she says. “This is the Mount Everest of habitual behaviour. You can’t just destroy it. What you need to do is wind down one habit and develop another one, so that, beside Mount Everest, you’re building the small pebbles of a new behaviour.”

I tell Jezuita that I worry I am letting myself off too easily by not going cold turkey. “You know, in the west, we’re taught to think of ourselves as inherently bad, like there’s something iffy and dirty about us and we have to be constantly kept in check,” she says.

Jezuita helps me to calibrate my expectations to something more realistic – reduction, with the aim of stopping, but in a kinder and less self-loathing way. She also encourages me to savour the taste of Diet Coke. “Really enjoy it,” she says. “Every time you have a drink, sit down and let the world stop for a minute.”

My morning Diet Coke rapidly becomes the best part of my day – I crave it in an animalistic way and I eke it out in tiny sips to make the precious cola last as long as possible.

***

Week three: a week without Diet Coke. I anticipate this like I do a cervical smear, only with less enthusiasm. On my first day, I feel like I am going to cry. I miss it. I miss Diet Coke.

The hypnotherapist and addiction specialist Jason Demant has helped people beat far tougher addictions. “Cocaine, alcohol, that sort of thing,” he says. He probes my childhood, my adolescence, the connections I make when I contemplate the supreme majesty of a can of Diet Coke. I explain the teenage eating disorder, filling up on Diet Coke instead of having lunch. I am fully recovered, I explain, but Diet Coke has stayed in my life nonetheless.

“Do you often feel like you have to toe the rules in your life?” Demant asks. “Are you always a good person? Do you always do the right thing?”

Yes, I respond, slowly. I work hard at my job, I try to be a good friend and partner, to eat well, to exercise. Diet Coke is the one thing where I think: fuck it. I am going to do what I want to do, which is drink gallons of this stuff.

Demant explains that Diet Coke is triggering my inbuilt reward system, which is why I can’t seem to let it go. “It’s a break from the obligations of life. What you need to do is find something else that gives you that feeling. What about, instead of rewarding yourself with Diet Coke, you could do things for yourself that felt loving?”

I incorporate small gestures of self-care into my day. I spend more time playing with my cat. I watch trashy TV. I read in the bath. In the twilight period between brushing my teeth and going to bed, I listen to the hypnotherapy recording Demant sent me after our session. “You have no need to drink Diet Coke,” Demant intones over a gentle piano soundtrack. Yes, I nod. I don’t want it.

Something miraculous starts to happen. I stop thinking about Diet Coke. There is no longer any Diet Coke in my fridge – and it is OK. I don’t miss it. To my astonishment, I lose a kilo. I am indifferent to the weight loss, but it is fascinating. It suggests that the artificial sweetener in the Diet Coke was triggering my appetite for sweet things. (Studies have shown a link between drinking diet drinks and higher sugar consumption.)

More than anything, I feel peaceful. “When you’re addicted to something, your brain is always thinking about where you’ll get the next hit,” says Marlow. “Drinking five cans of Diet Coke takes up a huge amount of brain space.” She is right: although I still think about Diet Coke, it doesn’t consume my thoughts like it used to. I am not constantly monitoring how many cans I have in the fridge, or when I next need to do a supermarket run.

Demant explains that I have to be watchful in the future, so I don’t slip into old habits. “With any pattern that is compulsive or addictive, you have to be on the watch all the time,” says Demant. “Because you may think: ‘Oh, I’ve conquered this,’ and then five minutes later you can go to the shop to buy Coke. Always be on guard.” Marlow agrees. “What we know with most addictions is that people relapse when they think they can have just one,” she says. “For many people, it’s simply not possible. My advice is: don’t think you can just have one can. It’s not worth it.” Marlow has not drunk a Diet Coke in five years.

It has been a month now and I no longer drink Diet Coke. When I take out the recycling, it doesn’t sound like a steel band at Notting Hill carnival. I drink water in the morning – and I like the taste of it. I have swum out of the foaming caramel tide into an ocean of clear, clean sea: water all around me and not a drop of fizz to drink.