A new regimen is being hailed by doctors as a healthier alternative to the controversial but highly popular Atkins Diet.

Called the GI (low glycemic index) diet, it is designed to distinguish between “good” and “bad” carbohydrates. It rates foods from 0 to 100, with glucose as 100, based on their effect on blood sugar levels.

It concentrates on the so-called “good” carbohydrates which keep a person feeling full for longer, reducing the urge to snack.

Dieters can stick to a fairly conventional balance of protein and carbohydrates, rather than skewing the diet toward high-protein foods such as meat, eggs and cheese.

Although many have lost weight on the diet, scientists have voiced fears over potential links to diabetes, bowel cancer and breast cancer. In a study published in The Lancet, two sets of rats were fed nearly identical diets, composed of 69% carbohydrates.

For one group, this was made up of “good” carbohydrates with a low glycemic index, the other “bad,” high-GI carbohydrates.

After 18 weeks, the high-GI group had 71% more body fat than the low-GI group, with much of the fat concentrated around the middle of the rats' bodies.

Fat around the middle of the body in humans produces the “apple” shape, which is a known risk factor for heart disease. Levels of blood fats were nearly three times higher in the high-GI group, another heart disease trigger in humans. Tests also showed changes in the high-GI group associated with an increased risk of diabetes.

In a second study, using mice rather than rats, the results were even more marked, with the high-GI group carrying 93% more body fat than the low-GI group.

Dr. David Ludwig, of the Children's Hospital, Boston, who led the research, said, “The Atkins diet tries to get rid of all carbohydrates, which is excessively restrictive. You don't have to go to this extreme if you pay attention to the glycemic index and choose low-GI carbs.”

High-GI carbohydrates such as white bread, refined breakfast cereals and concentrated sugars are digested rapidly, causing a surge of blood glucose and insulin.

Low-GI carbohydrates such as wholegrains, fruit, vegetables, noodles, lentils and many nuts release their sugar more slowly.

Previous studies have suggested a low-GI diet is beneficial, but it has not been clear whether other factors, such as fiber, contribute.

Ludwig said, “This is the first study that can definitively identify glycemic index as the active dietary factor. It can have dramatic effects on the major chronic diseases plaguing developed nations obesity, diabetes and heart disease.” Dr. Sarah Brewer, medical adviser to Atkins, said, 'People will lose weight more easily and more quickly following a low-carb diet.

“The conventional mix of carbs and protein is not correct for many people, which is why we have such an obesity problem now.”