A high protein, low carbohydrate diet is most effective at reducing hunger and promoting weight loss, at least in the short term, new research suggests.

But these diets - like the celebrity Atkins diet, zone diet and blood group diet - are not suitable for the long term, it is claimed.

The findings were made by scientists at Aberdeen's Rowett Research Institute. Cameron Stout, a former Big Brother winner, was one of the guinea pigs who helped provide the evidence.

The findings have just been published in the American Journal of Clinical Nutrition.

Stout was one of a team of healthy, obese men who were given two different diets during their stay in the Rowett's Human Nutrition Unit. Both diets had a high protein content (30% of total energy value) but they differed in the amount of carbohydrate.

One was low in carbohydrate (4%) and the other contained a moderate amount of carbohydrate (35% total energy value).

"Our volunteers found both diets to be equally palatable, but they felt less hungry on the high-protein low-carbohydrate diet compared with the diet which contained high-protein but moderate amounts of carbohydrate," said Dr Alex Johnstone, the Rowett's weight-loss expert who led the study.

"Weight loss during the two four-week study periods was greater on the high-protein low-carbohydrate diet, averaging 6.3kg per person, compared with 4.3kg on the moderate carbohydrate diet."

An important part of the study was to unravel the physiological mechanisms behind this type of diet. It is known that, when people eat low carbohydrate diets, within a relatively short time their body has to switch from using glucose as a fuel to using something different called ketone bodies. These are appetite-suppressing and they may have an effect on the appetite centres in the brain. It's also well-known that protein itself is very good at making people feel full-up.

"In this study, we showed that on the high-protein low carbohydrate diet the volunteers became ketogenic within one to two days of starting so it may be that high-protein, low-carbohydrate diets are particularly effective because of the combined effect of the protein and the ketone bodies," said Dr Johnstone.

"We showed that the volunteers on the ketogenic diet reduced their energy intake without increasing their hunger and this was a very important factor in their ability to stick to the diet."

However, Dr Johnstone warned: "A paper published last year from the same study showed that low-carbohydrate diets may have consequences for the health of the gut by dramatically reducing the numbers of particular types of bacteria. We will be looking in more detail at the complex way in which we respond to changes in our diet before we can say whether low carbohydrate ketogenic diets are a suitable tool for everyone who wants to lose weight.

"I wouldn't recommend it as a diet for healthy eating or weight maintenance. It is very much a tool to get the weight off."

Cameron Stout, who lost just over 12 kg during his nine-week stay at the Rowett, expressed surprise at not feeling hungry during the study and said he had adjusted to eating smaller portions.

"I had a great experience with at the Rowett," he said. "The food was excellent and the staff looked after us very well. Because I have such an irregular lifestyle I don't find it easy to stick rigidly to all that I learned while I was at the institute, but I try to make an effort most of the time."

Healthy choices

Typical menu for the high protein, low carbohydrate diet.

Breakfast choices

  • scrambled eggs,
  • grapefruit,
  • omelette,
  • yoghurt,
  • grilled tomatoes.

Lunch choices

  • chicken breast salad,
  • prawn and salmon salad,
  • cheese and chicken Caesar,
  • pork salad.

Dinner choices

  • chicken curry,
  • pork grill,
  • chicken creole,
  • chilli beef,
  • ham stew.

No alcohol would be permitted but tea, coffee and diet drinks would be allowed.