Bagels for breakfast! Burgers for lunch! The eat-all-you-want diet

Is the latest US slimming fad too good to be true? Jonathan Thompson and Karen Hall report

It sounds like a dieter's dream: a weight-loss regime that allows you to eat absolutely anything you like, including chocolate, cakes and hamburgers. But as publishers prepare to unleash the latest US dieting fad on this country, medical experts and nutritionists are warning consumers that there is no such thing as a free lunch.

It sounds like a dieter's dream: a weight-loss regime that allows you to eat absolutely anything you like, including chocolate, cakes and hamburgers. But as publishers prepare to unleash the latest US dieting fad on this country, medical experts and nutritionists are warning consumers that there is no such thing as a free lunch.

The so-called 3-Hour Diet has caused waves in America since its publication earlier this year, shooting straight on to The New York Times best-seller list. Devised by Californian fitness guru Jorge Cruise, its central tenet is that all food is good food - as long as it is eaten in the right amount and, crucially, at the right times. Weight loss, it argues, is not so much about watching the calories as watching the clock.

Followers of the diet are encouraged to eat a small or medium-sized meal of their choice every three hours - and are promised that they will lose at least 2lbs a week. A standard day involves six meals - breakfast, lunch and dinner with two snacks sandwiched between, and a treat before bed.

In the book, Cruise writes: "You'll ... never crave foods that are off-limits - because no foods are off-limits." He goes on to reassure readers that they can continue devouring "chocolate, bread or fast food".

Cruise, who made his name as the author of the best-selling 8 Minutes in the Morning fitness books, claims that the three-hour diet works by continuously resetting the body's metabolism, making it store less - and burn more - fat. By eating at the correct times, he contends, you turn off your body's "starvation protection mechanism" (SPM), which protects calorie-rich fat supplies. This encourages the body to burn fat instead of muscle tissue.

"By going more than three hours between meals, the body turns on its natural starvation protection mechanism and starts to burn muscle," saysCruise. "By eating every three hours, your metabolism stays revved and your body burns fat instead of muscle."

Cruise, who can already count British TV presenter Anne Diamond among his acolytes, claims that he understands the problems of dieting after his own struggles with obesity as a teenager.

His publisher, HarperCollins, hopes that Cruise - now tanned, toned and invariably grinning - can become the next Dr Atkins.

However, while The 3-Hour Diet continues to sell in its thousands on the other side of the Atlantic, British nutritionists have greeted many of the book's claims with scepticism.

Rebecca Foster of the British Nutrition Foundation warned that having meals every three hours would not only increase risk of over-eating, but would also have negative effects on dental health.

"This whole diet is based on an individual's metabolism, and how it uses the energy from food, but we'd like to see the science behind this," Ms Foster said. "As far as we're aware, this is not how the body would react if it hadn't eaten for three hours."

The Medical Research Council's Centre for Human Nutrition Research had a similar opinion of the book, which is due to be published here on 1 August.

Nilani Sritharan, a spokeswoman for the centre, said: "MRC research has shown that it is clearly what you eat - rather than when you eat it - that is important. During studies in Gambia with undernourished children, we have found that the best way to re-nourish them is by providing three meals a day. Increasing meal frequency increased propensity for eating more, and therefore gaining weight."