Doubts over good carb diet claims

Nutritionists have cast doubt on a Lancet study showing cutting out "bad" carbohydrates leads to weight-loss.
They were commenting on US research in the Lancet which showed the diet, which promotes foods with a low glycaemic index (GI) score - could be beneficial.

Foods with low GI scores keep blood sugars stable, eliminating the peaks and troughs which can lead to snacking.

But experts from the British Dietetic Association said cutting calories was still the key to weight-loss.


Eating fewer calories than you need is what will lead to weight loss
Ursula Arens, British Dietetic Association

The US team, which carried its research out on rats, is now planning an 18 month study on humans.
They said the diet, dubbed the "Atkins alternative" led to weight loss, reduced body fat, and reduced risk factors for diabetes and heart disease in the animals.

People on the traditional Atkins diet are advised to minimise their consumption of all kinds of carbohydrates.

But the low GI diet allows people to eat foods such as vegetables, fruits and wholegrain breads which are low in sugar, or which release sugar slowly.

High GI foods, such as white bread, potatoes and refined breakfast cereals, are rapidly digested, creating a surge in blood sugars.

There have been indications that low GI diets can be beneficial, but it has not been clear if this was due to other aspects of diet, such as fibre or overall calorie intake.

Controlled portions

The US researchers fed two groups of rats which were given diets made up of 69% carbohydrates.

However, one group of 11 rats was given high GI carbohydrates and 10 were given low GI carbohydrates.

The rats' meals were strictly controlled to ensure both groups maintained the same average body weight.

Researchers examined the animals after 18 weeks.

They found the high GI group had 71% more body fat and 8% less lean body mass than the low GI group.

In addition, the high GI group had fat concentrated in the middle of their bodies. In humans, this produces the "apple" shape that is a known risk factor for heart disease.

They also had higher levels of triglyceride blood fats, another heart disease risk factor in humans.

The rats also showed the sort of changes linked in humans to a high-risk of diabetes.

In a further experiment, 24 mice were randomly assigned a low or high GI diet.

After nine weeks, the high GI group had 93% more body fat than mice on the low GI diet.

Ice cream

Dr David Ludwig, who led the team at the Children's Hospital in Boston, said: "The study findings should give impetus to large-scale trials of low GI diets in humans.

"What the study shows is that glycaemic index is an independent factor that can have dramatic effects on the major chronic diseases plaguing developed nations - obesity, diabetes and heart disease.

"This is the first study with hard endpoints that can definitively identify glycaemic index as the active dietary factor."

He added: "The Atkins diet tries to get rid of all carbohydrates, which we think is excessively restrictive.

"You don't have to go to this extreme if you pay attention to the glycaemic index and choose low GI carbs."

However, a spokesperson for the Atkins Foundation, said it was "a myth" that the diet tried to eradicate carbohydrates.

"Atkins is about restricting refined carbohydrates such as sugar and white flour, while encouraging the consumption of high quality carbs."

Ursula Arens, a nutritionist and spokeswoman for the British Dietetic Association, told BBC News Online she was unconvinced the findings in rats could be converted to humans.

She added that looking at GI scores should not be the only consideration in a diet.

"If you stuck to foods which had a low GI score, you would be able to eat lots of ice cream - which are low GI foods, but not bananas or rice - which are high.

"And there are many, many people in China and Japan who eat lots of rice every day and are not overweight."

Ms Arens added: "Glycaemic index may play a small part, but there's no getting past the basic fact that eating fewer calories than you need is what will lead to weight loss."

Her views were backed by Dr Toni Steer , a nutritionist with the Medical Research Council who said, although the study was interesting, the issue of how GI foods affected health was "more complex in humans than in rats".

http://news.bbc.co.uk/1/hi/health/3604384.stm