We all know the nutritional rules, don’t we? Crash dieting is just a code for losing muscle and water. As soon as we stop, we’ll simply regain the weight — and, likely, plus some. Yo-yo dieting will merely mess up your metabolism.

In spite of this, we’ve kept doing the crazy diets. The bottom line was that we were thin. So what if we fasted for 48 hours, drinking only water, diet cola and black coffee, then munched a 400-calorie meal, then fasted again for 48 hours more? We lost 1st in four days — even if it was dangerously extreme. My own life has borne witness to the Scarsdale diet: I had a green salad and no cake for dinner on my 16th birthday. I lived through “Smashgate”, a regime of Smash mashed potato, for days, until I realised that it was about 10 times as calorific as I’d thought. At university, it was all about calorie counting — anything from 700 to 1,200 calories a day. In my first job, I worked through a haze of starvation on the simple but deadly “stone in four days” plan. I picked Thursdays for the first night of a fast, so I could offset dinner hunger pangs by late-night shopping at Topshop.

Sooner or later, most of us say goodbye to this miserable way of life. When sensible women want to lose weight, we rethink emotional eating patterns, up the exercise and get sustainably healthy, losing 1lb per week tops, right?

Maybe not. We could all be about to head back to the weird world of crash dieting. For new research from Tufts University in Massachusetts says that crash diets can actually work better than slow weight loss. Susan Roberts, professor of nutrition and psychiatry at Tufts, says the latest research from her lab shows that “sensible, healthy crash diets actually do as well for long-term success as slow diets and, for some people, can actually work better”.

She distinguishes between good and bad crash diets, however. The one she advocates goes further than the usual 1,500 calories a day typically advised for women to lose 1lb per week, but is not extreme, never dipping below 1,200 calories for women (or 1,800 for men). “We studied two groups, in which we cut either 10% or 30% of calories, and tried to keep them at it for a year,” she explains. “In the end, they were in a similar place — the 30-percenters definitely did not do worse, despite having a more stringent programme.”

What is more, she adds, people who get tempted easily may be better candidates for fast, strict diets than gentle weight loss: “A small calorie cut can work for the sensible crowd, but seems to almost backfire for people who get tempted by food. Disinhibited eaters [a psychological term referring to people who give up on diets easily when presented with food opportunities] actually did really badly on the 10% diet.”

Certainly, if you’re addicted to overeating, it can be easier dramatically to cut out all your favourites, rather than learn moderation, which is perhaps why meal-replacement diets have been found to be one of the most successful ways to lose weight (see Simon Glazin, above). “Despite the hype about slow diets being better, there has actually been very little research into whether losing weight fast or slowly works better in the long run,” argues Roberts. “The trouble with slow diets is people tend to feel they are getting nowhere and give up. Fast keeps you excited and feeling like you’re making progress.” Other experts take a very different view and insist any kind of diet is bunkum. “Diets depend on failure,” says the psychotherapist Susie Orbach, who has explored women’s attitudes to eating in such books as Bodies. “They need to fail, otherwise there would be no repeat customers.”

Others, such as Dr Peter Rowan, an eating-disorder consultant from the Cygnet hospital in London, warn that dieting and eating disorders go hand in hand. “The large majority of patients with anorexia and bulimia have the illnesses triggered by weight loss. Even a sensible weight-loss diet can trigger an eating disorder in someone who is vulnerable, but there is evidence to suggest that the more severe the weight loss, the more likely the diet is to trigger an eating disorder.”

Roberts dismisses extreme crash diets that promise huge losses, as well as fasting, as “snake oil”, but says that to lose as much as 20lb in eight weeks on 1,200 calories a day, plus 30 minutes’ daily exercise, is safe, provided the diet is balanced, with plenty of low-GI, high-protein foods to keep you full. And the weight loss will last, she says, if you “change what you eat permanently” to generally healthy habits.

Dr Shahrad Taheri, director of the weight-management clinic at the Heart of England NHS Foundation Trust, agrees that 1,200 nutritious, low-GI calories per day is the lowest a woman should go, but warns: “Most people’s weight problems occur over a number of years and reflect a lifestyle of selecting calorie-dense foods combined with reduced physical activity — this needs time to change.”

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