By day five without food, there is no hiding from the truth: I smell bad. Really bad. Not sweaty, but like something that’s been left in the bin too long and is rotting.

At first, lying in bed on a beautiful sunny day, with the windows open and the breeze blowing in, I think a backpacker must have left chicken carcasses in the bins in the neighbouring park. Revolting, I think, whoever left meat out to rot is gross. (Or in my slow state of cognition, what I actually think is: smell meat bad, chicken, gross, rotting backpacker.)

That is what I am smelling now. Rotting meat. It’s grim. After closing my bedroom window I realise with horror that the rotting smell has not gone away. It is worse. And it is coming from within me. Even my tears smell bad.

Is this part of the cleaning process, I wonder? I ask Associate Professor Amanda Salis about this odour. She says, “Bad breath is associated with fasting. This is partly due to ketones. There is also less hydration of the mouth, so saliva is not replenished. Skin cells in your mouth rot by bacteria that produce gases that smell bad.”

She can’t explain my whole body smell.

Dr Liu warned of smells in his materials, which I am now consulting constantly: “You may have bad breath because your body is releasing toxins, you could brush your teeth as many times as you like, but no chewing gum.” The pamphlet is silent on the issue of body odour. I apply expensive lotions to my skin and start showering more than once a day, but nothing is removing the smell.

This fast has turned me into a bedroom depressive with very little in the way of social engagements (no one wants to hang out with you when you are not eating) but I resolve to have no contact with anybody while I smell like this. People will gag – possibly vomit – if I get too close. I decide that when I am forced to interact with someone, I will stand at least 50 metres away from them and shout, or communicate via text message. The fasting clinic staff don’t count because the clinic itself has a weird smell.

Despite smelling like an open drain, being foggy in the head, feeling constantly miserable and listless, behaving in a disgusting and weird way in public, having bloodshot eyes and doing strange things late at night (I have been chewing pantry items and then spitting the ball of stuff into the bin and putting heaps of tissues over the clump of masticated food – a trick used by anorexics) and almost being killed by traffic – I am getting thinner! Much thinner! By day six I have lost 5.3kg. It’s the most weight I have ever lost in one go. The weight is coming off my face, my chest, my stomach and my thighs. I am shrinking, like a grape turning into a sultana.

While I should feel pleased that the fast is having one of its desired effects, my life is the most boring it’s ever been. I can’t focus on anything on TV for longer than 10 minutes and I can’t concentrate on reading unless it’s cookbooks, which I stare at – not reading so much as horsily inhaling pictures of super-stylised food in a sort of magical thinking that equates gazing to grazing. The body will find a way through one of its senses. If it can’t taste, it will smell and if it can’t smell it will gaze – like the thirsty stare reserved for someone you desire but can never have.

I have recently read David Foster Wallace’s The Pale King. He was doing the hard sell on boredom in that novel, convinced it was the road to bliss. It was just like the icy mountain pass – you only reached nirvana once you moved through it. He wrote that “dullness is associated with psychic pain” because it doesn’t provide enough stimulation to distract people from the deeper pain “that’s always there”.

So here I am, just me and the dullness and its evil cousin, psychic pain. In those weeks when I am fasting, the spectre of meaninglessness lurks everywhere. I wonder if it has been there all along, covered up with food ’n’ stuff – or if it is making its first appearance. You see, once you take everything away – the shopping and the eating, the preparing and the cleaning up, the cooking and the cafes, the friends and the restaurants and the parties and the drinks (all the drinks!), the quiet morning coffee with the paper in the sun, the barista who knows your name and the barman who reads your mood, the celebrations and the dates, the routines and the rituals – once you throw all that away, a sort of hush descends. In it you can see and feel and know the emptiness that is in the room before the room where the meaninglessness resides. In its bland way, it’s quite terrifying.

I’ve always been a social animal. I’m an extrovert who gets my energy from being around people. I love going out, I love gatherings and conversation and parties – just being with other people. During my fast, it is apparent how much socialising (probably 90% in my case) takes place over food and drink.

The isolation of the fast is hard going. In Down and Out in Paris and London, Orwell said the worst aspect of hunger was boredom. That and the sense that when you take food away, you take some essential human dignity away. “You discover that a man who has gone even a week on bread and margarine is not a man any longer, only a belly with a few accessory organs.”

By the end of week one, I’m going out of my mind. It has been boring, but also incredibly self-absorbed. The clinic staff and I attend to my body as if it is some fragile holy relic to be studied and turned over, applying mysterious treatments to restore it to some glorious past. (Did my body ever have a glorious past? Maybe when I was a child?) To quote writer David Rakoff, who fasted to find enlightenment: “My days are taken up in this narcissistic rumination about intake and output . . . This is one of the most self-obsessed things I have ever done in my life. And I say this as a first-person journalist.”

When I feel strong enough to go out and not eat (not steal food, or lick food, or spit chewed-up food into public bins), I make arrangements to meet a friend for dinner. Chris is coming to Sydney and wants to go out in Kings Cross. It would be ridiculous not to see him. Chris used to meet me for lunch in Melbourne; lunches that would roll into cocktails then supper, glasses of wine into bottles, bottles into more bottles. We hopped from rooftop bar to rooftop bar, the ones where you could smoke. There were nights when the city blazed and things sped up like in a time-lapse video: there’s the Princess Bridge at dusk, the Yarra at night, all inky and black, the small bar above Degraves Street and the restaurant with the door under the stairs, credit cards thrown down, change not collected. We talk and talk and talk and talk, and never have to go home if we don’t want to.

How different this night is. He orders beer and I order water. He orders dinner and I order nothing. It’s weird. The vibe is off.

I have underestimated how uncomfortable people feel when they are eating and drinking and you are not. If you don’t eat together it unbalances the dynamic profoundly. I wonder if there is something deep in our DNA that makes us distrust someone who will not break bread with us. Perhaps there’s an ancient, primal fear of being poisoned that means we only relax if everyone is eating the same food – lest there be an assassin in our midst.

The fast has also been the longest I have ever gone without alcohol since I was a teenager – and one of the things I will have to learn as I emerge from my stinky-bedroom day-sleeper solitude is how to socialise without booze.

But my night with Chris turns out all right. We talk. He eats and has a couple of beers. I cave and have a small teaspoon of rice. Our friendship doesn’t fall apart because we aren’t drinking together. It turns out something great built on nights of a thousand cocktails is still pretty great if you take away the cocktails.

• Brigid Delaney’s Wellmania (Nero, $32.99) is out now