The first thing I want to say is that this is the last thing I ever expected to write. Over the years, I have contemplated joining the police, moving to Canada, and taking up darts, but even in my maddest moments I never saw myself doing this. The need I feel to make this disclaimer crystal-clear, however, is something I’ve been puzzling over. The only purpose it can serve is my own vanity – which, I have been surprised to discover, is my single biggest worry about becoming a vegan.

It has only been six weeks, so it’s still early days, and I could be wrong about this. But I don’t think the worst thing about going vegan is saying goodbye to all the lovely things I used to eat. I really like roast lamb and scrambled eggs and ice-cream, but the truth is that you can get used to anything. My problem with veganism isn’t the diet, but the identity.

Facebook Twitter Pinterest ‘These days it’s the height of fashion and – if you’re a celebrity – practically compulsory.’ Jay Z and Beyoncé. Photograph: Lester Cohen/Getty Images for NARAS

Veganism used to be so niche that I was in my 20s before I first met a vegan, but these days it’s the height of fashion and – if you’re a celebrity – practically compulsory. Famous vegans are ten a penny – Beyoncé, Jay Z, Jennifer Lopez, Brad Pitt. Unlike most celebrity lifestyle choices, any idiot with a Deliciously Ella cookbook can access the glamour of giving up animal products, which may explain why the number of vegans in Britain has almost quadrupled in the past decade to more than half a million. Living in London, one can’t fail to notice that even vegan fashion has assumed a newly confident air; the old passive-aggressive T-shirt slogans (“Vegan. Because My Body is Not a Graveyard”) have made way for knowing hipster humour (“All Hail the Kale”). On a street in Hackney where, last time I looked, crowds on the pavement meant a pub fight had spilled on to the kerb, hordes now queue patiently in the rain, like old Soviet Union shoppers, outside “the world’s first-ever” vegan fried chicken shop, the Temple of Seitan.

So I don’t worry about looking weird. I worry about becoming that person who thinks what they put in their mouth is important enough to merit a significant share of their time and energy every day. Who wants to be sourcing vegan mozzarella on holiday, forever scanning labels, making a nuisance of themselves at dinner parties? To me, it has always felt fundamentally precious, if not borderline narcissistic, to care that much about the purity of one’s digestive system.

That middle-age would force a reappraisal never even occurred to me. In my 20s, it was just about plausible to pass off a diet of Dime bars and Diet Coke as evidence of a life too fabulously busy for trivial distractions such as actual meals. By 45, however, it looks like self-abuse. After I was diagnosed with breast cancer 18 months ago, it altogether ceased to be an option and, for the first time in my life, I paid serious attention to the novelty of taking care of myself – not least because when surgeons, oncologists and nurses have done everything they can to save your life, there is a certain sense of obligation to do one’s bit, too. When nutrition is no longer a lifestyle choice but a medical necessity, eating food that might really kill you becomes patently idiotic – which is why I spent most of last year trying to adopt a healthier diet.

When nutrition isn't a lifestyle choice but a medical necessity, eating food that might kill you is patently idiotic

The problem, as anyone who has ever tried knows, is that it’s impossible to know if you are doing it right. There is quite possibly greater global consensus on how to solve the Israel/Palestine conflict than on what we should eat, and the more you learn, the less you feel you know. Is a low-carb paleo diet the answer? Is meat OK as long as it is organic? Will five a day do the job? Or is anything less radical than a strict raw-food regime a waste of time? Willpower is hard enough to sustain, even when you know it’s worth it. The possibility that it might, in fact, be pointless was enough to derail every diet I tried.

In the end, I could find only one way to make sure everything you put in your mouth is a good idea. The simplicity of the solution was irresistible. The problem, of course, is that nothing else about going vegan is remotely simple. Was I really going to find time to start shopping in specialist wholefood stores and soaking mung beans? The vegans I knew all promised that after a month I would start to feel so fantastic that the palaver would seem a small price to pay. This may be true, but I worried that faffing about with legumes would defeat me long before the fabled herbivore high kicked in.

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Was there, I wondered, an easier way to do it? Of course there was. I found a company in London called Detox Fit, a one-stop shop for lazy vegans, that offers a weekly delivery of gourmet meals. A sort of vegan ready meals on wheels, if you like. Run by a preposterously good-looking vegan couple, the company also provides an AA sponsor-style helpline to call should I find myself outside a kebab shop, having a wobble. If out and about on the high street and hungry, all I need to do is call and they will guide me to vegan options in the vicinity.

Unable to think of a reason not to, I signed up, and embarked on a three-month experiment with veganism. A finite commitment felt much more doable than a lifelong promise, but the very modesty of the challenge also made me anxious. With no excuse for falling off the wagon, what if I still did?

There are so many reasons to be vegan that it is hard to know which one would work best in a crisis of willpower. Health is mine, and the obvious one – but, in a reckless mood, I might decide not to care. Would thoughts of carbon emissions from cattle fortify me? Maybe the trick is to keep a mental archive of factory-farming photos, ready to deploy when necessary. Then again, what if world famine turns out to be the most compelling option? It might be an idea to memorise some eye-opening statistics about how many acres of grazing it takes to make a Big Mac, and how many people the same fields could feed if we planted crops instead. Adopting a belt-and-braces approach, I watched the appropriate documentary material online: Cowspiracy, Forks Over Knives and Earthlings.

Rather to my surprise, at the end of month one, I’ve had no need for either the Detox Fit hotline or my fortifying mental devices. Whatever had I been worrying about? The whole thing has been startlingly easy.

And then I was invited to a dinner party …