Everyone I know is on the Fast Diet, the 5:2, intermittent fasting ... call it what you will. I can barely go anywhere without people talking about it.
As they will tell you, you eat anything you want for five days of the week, and diet for two. This means fewer than 500 calories a day (600 for men) for two non-consecutive days a week. It has been billed as the diet that anyone can do.
Not since the days of Atkins has an "ultimate diet" been taken up by so many people.
I know as many men as women who are on it, and all claim to be losing around 2lb a week, giving them a steady weight loss over the months as they adjust to it.
The joy of it is its simplicity. The Atkins Diet, which became popular in the late-1990s, was tricky and no fun. All we did was eat endless protein, which made our breath smell. Robert Atkins, the American physician behind it, had a heart attack in 2002, leading many of his critics to suggest the high levels of saturated fat the diet encourages were to blame.
A decade later, the Dukan became the diet de nos jours. Billed as the weight-loss plan that the French wanted to keep secret, the Dukan was another protein-based regime that encouraged disciples to eat, on alternate days, a few vegetables. That the Duchess of Cambridge's mother Carole Middleton, with her admirably svelte figure, was said to be a follower only added to its allure.
However, Dr Pierre Dukan, the retired nutritionist who devised the regime, has been censured by France's national medical body for failing to observe medical ethics, after he prescribed a woman who wanted to lose weight in the 1970s an amphetamine-derived drug believed to have killed hundreds of people.
Now we have the 5:2. It burst into our consciousness last year, after the BBC broadcast a Horizon documentary in which Dr Michael Mosley showed how it not only helped him lose weight – 14lb over several months, and 25 per cent of his body fat – but dramatically lowered his cholesterol, too.
Mosley then wrote a book about his findings with the journalist Mimi Spencer, who recently showed off her 5:2-honed body in a national newspaper. Before her Fast Diet, she said, she "didn't have the confidence" to wear a bikini.
Well, I'm not after a beach-babe body. I just wanted to lose a few pounds, so I went and bought the book anyway. It is comprehensive and inspiring, full of all the reasons why the Fast Diet could work for me, meal plans with fewer than 500 calories a day, and tips on how to handle the dizzy spells from not eating much.
The authors recommend, perhaps sensibly, that a 5:2 adherent should try fasting on the same days each week. They suggest a Monday, after the over-indulgence of the weekend, and a Thursday, before the over-indulgence of the coming one.
Fair enough. I don't eat much anyway. I rarely eat breakfast, have something simple for lunch and then I eat dinner with my children. Then I snack, and maybe have a glass or two of wine ... but I figured I could cut those out with ease. The idea of two days eating very little sounded like a breeze – until I actually went on the diet.
I started on a Monday. All was fine at the beginning. I spent an hour or so re-reading the Fast Diet book at the breakfast table. It all looked good. I salivated at the recipes. I couldn't wait to make a tuna, bean and garlic salad.
Unfortunately, I then did nothing but fixate on food.
The Fast Diet menu planner suggests dividing your fast-day calorific intake over two, rather than three, meals: breakfast (one boiled egg and half a grapefruit) and a light dinner in the evening. I ate my egg without the customary buttered soldiers happily enough – but, unfortunately, the act of having breakfast seemed to kick-start my metabolism. I found I didn't just want one egg. I wanted two.
And who knew there were 155 calories in a boiled egg?
By lunchtime, I was uncharacteristically starving.
Cravings came upon me. I wanted cheese, ham, chocolate, an apple, two apples, maybe some cherries, yoghurt and ice cream, an iced bun ... worse, by dinner, I had started to feel faint. I was so hungry, in a rather obsessive way, that I couldn't think of anything to do but eat my tiny tuna salad and then go to bed, exhausted.
I assumed this was because I'd just started the diet. But instead of striding onwards on fasting days, getting some kind of energy from my denial and a sense of hope that the weight would come off, I became lethargic, negative and fixated on food.
This made everything worse. I started fantasising about all the food I would eat on non-fasting days. I felt pathetic. I found the minuscule amount of food almost insulting. It was like existing on air.
"It takes a while to get used to," says Dr Mosley of his diet. "Most people who drop out do so in the first two weeks, but you need to give it time. It's important to play around with the 5:2 idea and find a pattern that suits you. If you don't usually eat breakfast, stick with that."
So I stuck with that for another four weeks, but it didn't get any better. On fast days, instead of experiencing a primal rush, my energy levels dropped – and dipped lower as the weeks went by. Any weight-loss benefit was counteracted by the fact that on my non-fast days, I ate twice as much as I would normally.
I became bad-tempered. As, like many women, I have a history of erratic eating, my children didn't seem remotely surprised that I veered from an egg and cucumber for dinner one day to fried bacon sandwiches the next.
However, my being scratchy and exhausted upset them, to the point that they started trying to feed me.
"I am sad to hear that," Dr Mosley tells me. "The body does adjust. Remember, it's a general guideline: one diet doesn't fit all, but the general premise of cutting calorie intake to the quarter of what you are used to, on two days a week, does work. It does, however, depend on what your calorie intake was in the first place."
I'm not the only person to feel this way about the 5:2. I talked to a close friend who admitted she was finding it as hard as I did.
"I can't bear it," she said, as we toyed with some lettuce on one of our agreed fast days. "All I want to do is wolf down an avocado and cheese on some sourdough."
This seems to be a major drawback – that the denying of food leads to an insurmountable, joyless obsession with it.
It occurred to me that we have ended up doing precisely what we were supposed to avoid – making dieting difficult.
"No one diet fits every person," Dr Mosley reminds me. And, he admits, you can cut yourself some slack: "If you're lacking in energy, eat more than 500 calories. Spend your two days eating just protein and veg, or cut out carbs."
Mosley also suggests remembering that, on the days you are not subsisting on a boiled egg and a stick of celery, you can eat anything you want – from pizzas to chocolate waffles. Even better, as the entire planet seems to have embraced it, it is possible to be sociable and diet at the same time.
So, I am not giving up. I am taking Mosley's advice, cutting just the carbs and upping the calories and ... doing it my way.
And hoping it works this time.