Ten million of us are on diets. Now we will discover if it's a fat lot of good

Celebrities endorse it. Millions of us struggle with it. And doctors warn against it. Now, as part of its drive against obesity, the Government is launching an official investigation into the claims of Dr Atkins and his rivals in the £10bn British diet market

The Government is preparing to launch the first official investigation into the Atkins diet as part of a major inquiry into Britain's epidemic of obesity.

The Government is preparing to launch the first official investigation into the Atkins diet as part of a major inquiry into Britain's epidemic of obesity.

The National Institute of Clinical Excellence (Nice) will next month convene a panel of up to 20 doctors, nutritionists and dieticians to evaluate "low-carb" diets such as the one pioneered by the American Dr Robert Atkins, and the multimillion-pound diet industry as a whole.

At any one time an estimated 10 million Britons are dieting, one in three following regimes that, like Atkins, cut out all carbohydrates such as bread and potatoes, a trend that has caused alarm in the medical profession. Atkins is known as a "bacon and eggs" diet, because it endorsesunlimited amounts of fat, meat and protein, despite the risks associated with an unbalanced diet.

The inquiry into the prevention and management of obesity in England and Wales is the largest yet undertaken by Nice, which will work alongside the Health Development Agency on the project. Thousands of people, including singer Robbie Williams and actress Jennifer Aniston, say they have benefited from the Atkins approach. Celebrity backing has made the diet famous worldwide.

But Atkins has run into hostility from the medical profession. Britain's top nutritionist, Dr Susan Jebb, has condemned the theory behind Atkins as "nonsense". People lose weight using the diet, she said, because they eat less not because, as it has been claimed, Atkins dieters burn fat more efficiently. Dr Jebb, head of nutrition at the Medical Research Council, is one of many to criticise the Atkins diet as an unknown risk because there is no evidence about its long-term effects.

One study claimed that a low-carb diet could reduce women's chances of becoming pregnant. There are also concerns that high-protein diets may be linked to kidney problems, while eating carbohydrates could help reduce cholesterol and lower the risk of heart disease as well as improving digestive function and cutting the risks of bowel cancer.

There was further criticism, and some black humour, when it emerged that the founder of the diet, Dr Atkins, who died after slipping on a New York pavement in 2003, weighed a clinically obese 18 stone at the time of his death. A spokeswoman for Atkins rejected the criticism: "The Atkins Nutritional Approach is a scientifically validated strategy for weight control and good health based upon controlling carbohydrates. Currently 33 studies support and more than 700 published, peer-reviewed studies support the concepts underlying it.There is no convincing clinical evidence to suggest that it has any adverse effects on health."

Ministers are shocked by the increasing scale of obesity, and by a recent hard-hitting report from the Commons Select Committee on Health. It criticised ministers for failing to address the problem. Obesity has grown by almost 400 per cent in 25 years, with three-quarters of adults now overweight or obese. Childhood obesity has trebled in 20 years.

The inquiry, which will publish its draft findings in a year, will influence doctors' choice of treatment for overweight patients. News of the study has provoked a storm of lobbying from diet companies, including Atkins, and patients' groups. Low-fat diets, slimming clubs and "meal replacements" will also be assessed. Atkins has sent documents to the Department of Health, pressing its case that its dietary approach is safe and effective, and it will be one of more than 150 "stakeholders" consulted as part of the inquiry.

Atkins Health and Medical Information Services was recently given favourable publicity in a parliamentary question from the crossbench peer the Countess of Mar, who pointed to evidence of the diet's benefits. Nice last month agreed the "final scope" for the inquiry. The formal evaluations of the evidence will begin next month.

Meanwhile the diet business is booming. Britons spent around £10bn on diet books, magazines, food supplements and pills last year. Sales of potatoes fell by 4.5 per cent.

Dr Atkins published his first diet book in America in 1972, but it is only in recent years that his diet has become a global brand. Britain is the second biggest market after the US, followed by Japan and pasta-loving Italy.

The privately owned Atkins company last year launched its own branded food range to accompany the diet books. It is shy about revealing its profits, but admits that sales now run into hundreds of millions of dollars a year. Turnover is thought to be around £60m.

But the Atkins diet may have had its day. It has recently been rivalled in popularity by the South Beach diet, devised by the Miami cardiologist Dr Arthur Agatston. The South Beach Diet book, which has sold more than seven million copies worldwide, offers a more complex picture than the Atkins diet by suggesting that some carbohydrates are better for the body than others.

Additional reporting by Tanya Angerer

WEIGHING UP THE PROS AND CONS OF FASHIONABLE DIETS

ATKINS

What is it? World's most famous "low-carb" diet. Users told to cut out carbohydrates such as potato and bread, eating unlimited fat and protein

What do they say? By restricting carbohydrates, Atkins claims that the body burns fat. Doctors say there is no evidence of this, or of its long-term effects

Celebrity followers: Robbie Williams, Billie Piper, Al Gore, Renée Zelwegger, Harvey Weinstein, Brad Pitt, Minnie Driver

EAT RIGHT 4 YOUR TYPE

What is it? A diet system recommending different foods for different blood types, based on the writings of American physician and author Dr Peter D'Adamo

What do they say? Nutritionists have condemned the theories as unscientific

Celebrity followers: Actresses Martine McCutcheon and Elizabeth Hurley, who said it sounded like nonsense, but that she successfully lost weight

SLIM FAST

What is it? A meal replacement diet consisting of two milk shakes or soups a day, followed by a normal meal in the evening. The drinks are fortified with essential vitamins and minerals

What do they say? Users complain they feel starved

Celebrity followers: Whoopi Goldberg was an advocate until she was dropped by makers Unilever for making anti-Bush remarks. Glamour model Jordan has also used it

SOUTH BEACH DIET

What is it? An approach devised by Dr Arthur Agatston which distinguishes between "good" and "bad" carbohydrates. It recently overtook Atkins at the head of The New York Times bestseller list

What do they say? South Beach promises weight loss of up to 13lb in two weeks, but critics claim this is water, not fat.

Celebrity followers: Bill and Hillary Clinton, actress Kim Cattrall

WEIGHTWATCHERS

What is it? A club approach based on a points system that doesn't ban any type of food, and on regular meetings with other dieters. One of the few programmes devised by a woman. Features group weigh-ins

What do they say? One of few dieting approaches favoured by the medical profession

Celebrity followers: Actress Claire Sweeney

THE ZONE DIET

What is it? Meals are made up strictly of 40 per cent carbohydrates, 30 per cent protein and 30 per cent fat.

What do they say? The diet says the body works with a performance "zone" and weight is lost gradually. Critics say that calculating what to eat is cumbersome

Celebrity followers: Singers Madonna and Janet Jackson, actress Jennifer Aniston - who switched to the Zone Diet from Atkins