The high-protein, low-carbohydrate Atkins diet that has become the fashionable way to lose weight was criticised as "pseudo-science" by health experts on Tuesday.
The eating habits encouraged by the diet, which favours consumption of eggs, bacon, meat and cheese and frowns on bread, pasta, fruit and vegetables, might help people shed the pounds in the short-term but poses long-term problems.
It is popular because it allows consumption of fatty foods and is a favourite of stars including Geri Halliwell, Catherine Zeta-Jones and Renée Zellweger.
But Susan Jebb, head of nutrition at the UK government-funded medical research council, said: "There is nothing to persuade me it is a good way to improve your health. It is not even an experiment.
"Nobody is evaluating what is happening out there to millions of people who are following it."
There was evidence that carbohydrates and fibre, from foods including pasta, multigrain bread, beans and pulses, helped to guard against heart disease and cancer. There were also concerns that a high-protein diet might damage the kidneys in some people as well as cutting calcium intake, thus leaving people vulnerable to bone damage such as osteoporosis.
The diet represented such a change from the "healthy eating" approach recommended by government agencies at present that "serious long-term trials" would be needed to evaluate its impact, Jebb said.
Dr Robert Atkins developed the diet and published his bestselling recommendations in the 1970s.
It has made a comeback after years out of fashion. Atkins believed carbohydrates overstimulated production of insulin, provoking hunger, more eating and therefore leading to weight gain.
But Dr Jebb said the diet represented "pseudo-science" and a psychological crutch for people. She blamed the food industry for undermining government attempts to encourage balanced diets.