Fad diets do more harm than good

A study of fashionable diets followed by stars including Geri Halliwell and Jennifer Aniston claims they are a con and could actually be harmful.

Lyndel Costain, a consultant dietician in the British Dietetic Association, believes fad diets such as the "low-carb plan" and the "blood-type programme" have no basis in science.

She will tell the BDA's annual conference in Nottingham today that many of the diets pose a health risk because they demand entire food groups be cut out - causing followers to miss out on vital nutrients.

The study, based on the dietary success rates of 5,000 of Ms Costain's patients over more than a decade, focuses on four diets: Dr Atkins' Revolution (known as the low-carbohydrate plan), the Eat Right For Your Type diet (based on blood types), the food-combining diet and the cabbage soup diet.

Ms Costain says: "Eating plans like the low-carb plan and the blood-type programme mislead people. The bloodtype diet, followed by Martine McCutcheon, is a load of hogwash."

The Dr Atkins diet claims it works by restricting the amount of carbohydraterich foods, which overstimulate the production of insulin. It claims insulin makes you store fat. But Ms Costain, who specialises in the treatment of obesity, says the real reason people on this diet lose weight is simple - they eat less.

"Insulin can only make you store fat if you are taking in excess calories and this diet works by restricting the overall calories consumed. The diet will work in the short-term because it is low in calories - not because of their theories about insulin."

She warns: "It demands you cut out carbohydrate-rich foods, which are a good source of calcium. The early stages of the diet causes ketosis, where the body uses fat differently for fuel. Ketosis makes the blood and urine acidic, which causes the body to lose more calcium and potassium, which is not good for bone health. It also gives people bad breath and can make them feel light-headed or a bit nauseous."

Of The Eat Right For Your Type diet Ms Costain says: "This diet works on the theory that people with different blood-types should eat different types of food. Many of their programmes cut out dairy products. Any diet that cuts out whole food groups will be nutritionally inadequate."

She is also dismissive of the food-combining-diet, saying: "My main criticism is that its advocates suggest there is something magical about the way food groups are combined which causes people to lose weight. That is simply not true - if people on this diet lose weight it is because they are taking in fewer calories."

As for the final diet under the microscope, Ms Costain says: "The cabbage soup diet - advocated by Jilly Cooper - is certainly not nutritionally adequate. You may lose weight very quickly but it teaches you nothing about how to eat healthily. And the diet is so foul most people are unable to follow it for any length of time."

She concludes: "People are led astray by the scientific explanations for these diets. The only reason any diet works is because the person on it is taking in fewer calories than they are burning.

"When people fall off these diets, as almost everyone does, they feel hopeless and believe they will never lose weight.

"The diets may work for stars - who have an army of personal trainers and chefs to help them. But they should carry a health warning for people in the real world. The only way to lose weight in the long term is to eat healthily and take exercise."