Of all the questions that I go through life dreading, including “How’s the next book going?” and “Will I live to see your children?”, the one I fear most is: “Do you have any dietary requirements?” It’s not providing an answer that’s the difficulty: it’s simple enough explaining that I don’t eat beef, and that I avoid meat on Sundays and Tuesdays. It’s the subsequent “why?” that’s the problem.

You see, I’m not really sure why. I don’t eat beef because I was bought up being told that it was a transgression of my faith to partake of the Holy Cow. But I’ve since met strict Sikhs who disagree, and I’m not massively religious anyway, so there’s no real reason to continue to abstain.

Not eating meat on Sundays and Tuesdays is also a legacy from my youth. But whenever I ask for an explanation from my mother, she proffers a different superstitious explanation. And, apart from the occasions when I forget or give in to temptation, I continue generally to maintain the rule, even though I fancy myself as rational.

All quite bonkers. At least, I thought it was bonkers until an article in The Sunday Times demonstrated a truth to which Morrissey’s career has long been testimony: that if you behave bizarrely for long enough, eventually you’ll find that you’re fashionable. Apparently there’s a new diet craze in Hollywood for “part-time veganism”, or “agnostic veganism”, or “partial veganism”, with trendy types across Los Angeles mostly avoiding meat but “indulging occasionally”.

Of course, my peculiar dietary habits don’t tally entirely with this fad: if anything, it’s the vegetarianism, not the meat, that I avoid. And I don’t divide my diet in the way that these Californians do: the most popular way of being “vegan-lite” is to avoid meat and animal products until 6pm, then give in.

Also, I don’t do it for reasons of health, and I’m not vegan on Sundays and Tuesdays, but vegetarian. But these are minor differences. I’m not going to miss out on this rare opportunity to claim to be trendy. And, having been a part-time vegetarian, or a so-called flexitarian, on and off for 32 years now, I would say the attractions of the diet, as I follow it, are four-fold:

1. It’s a good idea to eat less meat. Even my colleague Giles Coren, who has complained recently that “vegetarianism is a cry for help”, “a sadly transparent attempt to exercise control over your body, which you feel the need to do for psychological reasons of which you are probably unaware” and “a way of controlling one’s food intake without drawing attention to one’s vanity”, has conceded that “current meat consumption levels are unhealthy”.

And he’s right. Too much flesh is bad for your health — eating more greenery can reduce the risk of developing some cancers by half, according to recent research — and the environment. According to the United Nations’ Food and Agriculture Organisation, livestock production is one of the major causes of global warming, land degradation and air and water pollution.

2. Full-time vegetarianism is unreasonable. I mean this not only morally and in dietary terms — certain nutrients, such as vitamin B12, are present in animal products but not generally present in plant products — but also practically. My mother is a proper, dedicated vegetarian, but manages only because she cooks everything herself and never eats out. I don’t know any other vegetarian — or, for that matter, any vegan, ovo-lacto vegetarian, pesco-vegetarian or fruitarian — who manages to keep to the rules in a sustained way.

This is reflected in the vocabulary that has cropped up around vegetarianism (people talk of being “psychological vegetarians” or “vegi-curious”); in the fact that 70 per cent of the 300,000-plus readers of Vegetarian Times are apparently “sometime” vegetarians; and in close examination of the dietary habits of famous so-called vegetarians who often turn out to be no such thing.

Sue Perkins, for instance, claims she is “largely vegetarian”, but spends a significant amount of her time on The Supersizers Eat . . . scoffing offal. The philosopher A. C . Grayling, meanwhile, recently remarked: “I’m a vegetarian, but I wear leather shoes. Some people say that’s a contradiction; I say I’m doing my best.” And Hitler, who is, of course, required by law to be cited in all articles on vegetarianism, was, according to Rynn Berry’s book, Hitler: Neither Vegetarian Nor Animal Lover, partial to the occasional sausage, stuffed squab, liver dumplings, ham and caviar.

3. Part-time vegetarianism is polite. A much-neglected downside of not eating meat is the presumptuousness and rudeness of expecting people to cook entirely different meals for you at your behest. Frankly, sometimes an animal sacrifice — and, for that matter, your principles and global warming — are a worthwhile price to pay for politeness.

I believe this so strongly that, despite a lifetime of avoiding burgers, I once even ate beef to save a host from embarrassment. I’d been invited for lunch in the City, which I thought was going to involve a couple of sandwiches with someone I’d corresponded with, but turned out to be lunch for 12. And when a massive beef joint was produced in my honour at one o’ clock, I just couldn’t bring myself to say I didn’t eat it — not least because the conversation had mostly focused on what this particular organisation could do to become more ethnically and culturally diverse. I felt terribly guilty afterwards, not least because it tasted absolutely fantastic, but part-time vegetarianism is flexible enough to allow this. Which brings me to the diet’s main attraction ...

4. Part-time vegetarianism requires almost no effort. Indeed, apart from those who survive entirely on sirloin or baked tortilla crisps with tomato salsa, most people already eat a mixture of meat and veg. In this respect, it’s the easiest diet in the world: try to eat more greenery occasionally but, apart from that, eat what you want, when you feel like it. Bon appétit.

sathnam@thetimes.co.uk

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