The 4:3 diet? 5:2? Overnight? Why your fancy New Year weight-loss regime won't work

From the 4:3 (son of 5:2) to the Overnight diet, the rash of new, fad weight-loss regimes have one thing in common: they don’t work

Fat chance: most people who embark on a New Year diet and manage to lose weight will immediately put it back on again (Rex Features)

I once invented my own New Year diet. I might have made a million if I had gone for it full pelt, worked it into a book and sprinkled it with the all-important celebrity stardust. But I lacked the application – and the celebrity friends. Not to mention the gall.

I called it The Wet and Dry Diet, and it has one rule: you may not eat wet and dry foods at the same time. You may eat anything you like, in any quantity, so long as you obey this single rule. That’s it. It would be a short book. I guaranteed then, and I do so again today, that if you follow my diet faithfully for three months, you will lose weight. It means that you may not eat breakfast cereals (dry) with milk (wet). Nor may you accompany pasta (dry) with sauce (wet) though a dusting of grated Parmesan is acceptable. Meat (dry) may not be accompanied by gravy (wet), but may be eaten with vegetables and potatoes, unless these are mashed or puréed. Get the idea?

The point of this diet is to make eating difficult. This – and here’s the genius – is the point of all the diets that are currently flooding the airwaves, magazines and newspapers. There has been a tsunami of them this year – the 4:3 (son of 5:2), the DODO (day on, day off), the Juicing, the Overnight, the Sugar Free, the Monomeals (one food only at each meal) – variously endorsed by celebrities including Gwyneth Paltrow, Cameron Diaz and Victoria Beckham.

And these are just the new ones. Still around and popular are the Paleo (caveman diet), the Alkaline (avoid acid foods), the Ornish (low fat), the TLC (“Therapeutic Lifestyle Changes”, aka low fat). Millions of people are following these diets – or trying to – and buying the books and programmes that help them do so. It is a multi-billion pound industry, grown fat on our collective anxiety about our expanding waistlines.

Yet we know there is only one way to lose weight. Eat less and do more. The task that the diet gurus face is how to help us achieve this simple but extraordinarily challenging goal. The answer – common to all – is to make eating difficult, so that we consume fewer calories, partly because obtaining them is so damned complicated, involving minute inspection of food labels, careful weighing of ingredients, deep alterations to shopping lists, and unfamiliar food-preparation tasks.

You might just as well tell people to stand on their heads while eating. It would achieve the same end. But it wouldn’t sell many books.

Last year, an estimated four in 10 British slimmers tried the 5:2 intermittent fasting diet and it looks like its successor, the 4:3 or Every Other Day Diet – where dieters fast on alternate days and eat normally the rest of the time – will prove just as popular. Fasting is, by definition, the most radical way of cutting calories.

But the 5:2 was not radical enough for some. It allowed consumption of a limited number of calories on a fasting day (500 for women, 600 for men). Hence the 4:3, to step up the pressure, and now the DODO, or Day On/Day Off diet, which requires complete fasting during the Day On, avoiding tedious calorie-counting.

A more timid version is the Overnight diet, the invention of weight-loss expert Dr Caroline Apovian, which starts each week with a “one-day power up”, during which only smoothies may be consumed – a fast of a (limited) kind. This is followed by a “six-day fuel up”, based on low-fat dairy, lean protein, whole grains and as many fruits and vegetables as you like. You may recognise this. It has been standard NHS dietary advice for at least the past 20 years – and available for free.

For sheer gall, however, the Joe Juice Diet takes some beating. Joe Cross used to be 100lbs overweight, stoked up on steroids and suffering from an autoimmune disease. Now, the American is set to be one of many faces of the juice diet in the UK this year, after he swapped fast food for fresh fruit and vegetable juices. He consumed nothing else for 60 days, made a film about it called Fat, Sick and nearly Dead, and has now released a book, The Reboot with Joe Juice Diet. Joe’s juice diet is simple: after the initial fast, which may last anything from a few days to a few months, it encourages people to increase their consumption of vegetables and fruit. Sound familiar? It has only been conventional medical wisdom for at least the past three decades.

The sugar-free diet, in its most extreme version, cuts out all foods that contain added sugars, in addition to fruit and any vegetables that contain natural sugars, such as parsnips, carrots and peas. Tricky stuff identifying which veg do and don’t contain natural sugars.

Simpler to follow, but less radical, is a version of this diet that involves eating fruit (but not juices) and vegetables and living without all added sugars, honey and processed foods that contain sugars. That rules out everything from packaged soups to sauces.

But simpler is also more difficult. It means meals must be prepared from scratch, using natural ingredients. Which spells success for the diet. Instead of having a ready-cooked microwave dish, dieters must peel onions and chop sprouts. It’s labour-intensive and time-consuming – and they end up eating less.

The Monomeals diet involves eating one type of food per meal, normally a particular fruit or vegetable. It could be a bowl of grapes, bunch of bananas or a plate of broccoli. Variations of this diet have emerged over the years – the Cabbage Soup Diet was an early example. If you are eating mainly cabbage, or mainly any one type of food, you will get bored and will eat less. Simple. Job done.

There is a danger, with all these diets, of taking them to extremes. The consequences are unpredictable, but mostly not good. A surgeon once told me of his alarm, when opening up the abdomen of a patient, to discover all his internal organs stained a deep orange. He had been living on carrots.

Obesity experts learnt years ago that searching for the most effective diet was like looking for El Dorado – it was doomed to failure. It was not the diet that determined how much weight you lost, but the rigour with which you followed it. The new challenge was how to match individuals to the diets that best suited them. A new term was coined: nutrigenomics – the science of increasing adherence rates to promote weight loss. If success in dieting depends on the individual’s psychological determination to change, then it is up to dieters to select the diet that works best for them. That means finding the diet that most effectively eases the demands on willpower.

The need to do so is more urgent than ever. The National Obesity Forum warned earlier this month forecasts that half the population could be obese by 2050 if sufficient action is not taken may have understated the true scale of the crisis. Public Health England recently predicted that 60 per cent of men, 50 per cent of women and 25 per cent of children could be obese by that date. It is easy to say that something must be done, but harder to decide what, at least where dieting is concerned. Official advice is to avoid “fad diets” which promise rapid weight loss – because of the difficulty of keeping the pounds off when the diet ends.

The NHS Choices Live Well website advises: “It can be tempting to put your faith in one of the countless schemes that promise rapid, easy weight loss. Unfortunately, even if these fad diets do help you to lose weight you are unlikely to maintain a healthy weight in the months and years afterwards.”

The grim fact is that most people who start a New Year diet and begin shedding pounds will ultimately put them back on again, and frequently end up heavier than they started.

One in four people in Britain are said to be dieting to lose weight at any one time. They expend large amounts of effort and huge amounts of money buying special foods, joining diet clubs and counting calories. They will suffer from the constant hunger and the loss of one of life’s great pleasures – eating – and when they fail, as most ultimately will, they will feel guilt and self-hatred. Only a small minority will successfully lose weight and keep it off for more than five years, research suggests.

For the rest, whose weight bounces back up again, there is an additional caution. Repeated on a regular basis, yo-yo dieting may be damaging to health. Research has shown that repeated rapid weight gain and loss may increase the risk of heart disease, heart attacks and premature death. Some diets claim to alter metabolism so that calories are burnt faster or absorbed more slowly. But if there is any effect on metabolism – and this is disputed – the effect is minimal. The reason for the obesity explosion in Britain – where an estimated 27 million adults are obese or overweight – and across the Western world, is that an energy imbalance has built up as we consume more and do less.

The most successful diet of all time is the Atkins diet – but only if you are counting £s rather than lbs. More than 45 million copies of the Atkins diet books have been sold since the 1970s. It recommends unlimited consumption of butter, fatty meat and high-fat dairy products, while carbohydrate intake is restricted to 30 grams a day, equivalent to a small potato.

Research suggests that it is safe and effective at promoting weight loss in the short term – calorie for calorie, protein appears to be more satisfying and thus better at curbing appetite than fat or carbohydrate. But, in the long term this is a diet practically guaranteed to induce heart disease. People who stuck with it for more than a year suffered headaches, muscle cramps and diarrhoea caused by carbohydrate deficiency. The minimum requirement of carbohydrate for an adult is 150 grams a day, but on the Atkins diet it is cut to one-fifth of that.

Is dieting worth it? It depends why you are doing it. To get into that size 10 dress for a wedding? Certainly. To improve your health? It depends how overweight you are to start with.

For the severely obese, losing weight may be life-saving. But for the merely overweight, the benefits – if any – are less certain. There is no guarantee that shedding pounds will improve their health.

What we do know is that the obese – those with a body mass index score of 30 or over – are at greater risk of ill health from heart disease, diabetes, some types of cancer and joint problems. Obesity is estimated to cause at least 30,000 excess deaths a year in the UK.

But there is scant evidence to show that losing weight will cut the risk. Does a person who loses 20 pounds acquire the reduced risk of a person who started out 20 pounds lighter? We do not know.

The moral is do not waste time deciding which diet to follow. Low-carb or no-carb, high or low fat, protein rich or poor – it makes no difference. It is not the diet that determines how much weight you lose but the determination with which you follow it. Not just this week or next, but over months and years.

Better still, of course, to avoid putting the weight on in the first place. But if you have read this far, it is likely too late for that.