Ever since Hippocrates told overweight people to walk around naked and sleep on hard beds, the quest for slimness has been powered by self-denial.
Today's mad diets include the Russian Air Force Diet, the Cabbage Soup Diet and the Caveman Diet. But one fad stands head and skinny shoulders above the rest.
Its devotees include undernourished actresses such as Jennifer Aniston and our own (now extremely) Minnie Driver, who claim that they can eat unlimited quantities of bacon and eggs for breakfast, guzzle steaks and cream for lunch and tuck into fried chicken at night - and still the pounds fall away. The catch? They can't eat any bread - or buns or cakes or rice or pasta or potatoes, or indeed anything containing carbohydrates. Carbs, as the fashion afficionado would say, are the new fat.
For the past decade or so, fats have been banished from the plates of anyone wishing to lose weight. The general dietary consensus is that you fill up instead with carbohydrates, fruit and vegetables. So how (or, perhaps more importantly, why) has the incredible shrinking Aniston shed 30-odd pounds by following a diet called the Zone? Well, here's the science: if you cut the carbs from your diet, your blood-sugar level drops. Your pancreas then produces less insulin, and less insulin means that your body starts burning fat.
The fact that at a conference last week 9,000 US doctors and dieticians branded low-carb diets "a nightmare" seems no deterrent. Currently topping the New York Times paperback bestseller list for advice books is protein king Dr Atkins (no relation) and his New Diet Revolution. Atkins's immense sales are followed by a host of other low-carb evangelists whose books have titles such as The Carb Addict's Diet, Protein Power and Get Skinny on Fabulous Foods.
But as the trend shimmies its way across the Atlantic, British health professionals are getting edgy. "Cutting entire food groups from your diet is dangerous," warns Dr John Hunter, consultant gastroenterologist at Addenbrooke's hospital in Cambridge. "A healthy diet, even if you're trying to lose weight, is one in which you get 50% of your calories from carbohydrate, 35% from fat and 15% from protein.
"Carbohydrates are the body's preferred energy source. Without them, the body will get its energy from fat, but this increases your risk of things like heart disease, gallstones and arterial disease and could raise your cholesterol level."
And while in the short term cutting out carbohydrate may not do you much harm, "In the longer term, it will increase the metabolic load on the liver and kidney, and could permanently damage them."
Dr Gail Goldberg, a senior nutrition scientist at the British Nutrition Foundation, is equally appalled. "This is against all the advice we give about reducing fat to lower cholesterol levels, and increasing your carbohydrate intake." Carbohydrates aren't found only in foods like bread and rice, says Goldberg. "Fruit and vegetables are carbohydrates too - and are vital sources of fibre and vitamins." Along with kidney failure, then, you could develop vitamin deficiencies, bad breath, constipation, dehydration, weakness and nausea.
Goldberg believes that the diets have worked mainly because they are restrictive: while you'd guiltily scoff a second slice of cake, you're unlikely to reach for another steak. You therefore eat less and lose weight. So behind this latest fad lurks that old message that none of us likes to hear: cutting calories and exercising more is the only way to lose weight. "Energy is energy," says Goldberg. "It makes no difference whether the excess calories come in the form of fat, protein or carbohydrate."
Surely the fact that actresses like Aniston and her Friends co-star Courteney Cox are disappearing in front of our eyes should be a cause for concern, not emulation. One of the few sensible voices seems to be that of Aniston's ex-personal trainer, who said: "She lost body fat, seemingly all of it, by drastically reducing carbohydrates... now she is positively emaciated."
It's probably no coincidence that this fad originates in the US, where 54% of the population are classed as overweight. Drastic diets don't encourage healthy, sustainable eating patterns. You lose weight rapidly. You start eating forbidden things again. You put the weight back on. You diet again. And after a while your metabolism is permanently disrupted.
Above all, it is our brains that need the energy supplied by carbohydrates. This could explain why Dr Rachael Heller, co-author of The Carb Addict's Diet, feels compelled to blame her erstwhile obesity on the "carbohydrate craving gene", located, she says, "on chromosome number 11, close to the alcoholism gene and the cocaine-addiction gene".
That'd be just down from the cashing-in gene, then?
