Most effective diets ‘are high-protein and low-carb like the Atkins’ – but should not be used for more than six months

THE most effective diets are high-protein, low-carbohydrate ones like the Atkins and the Caveman, a survey has found.

A study found people following the low-carb diets lost between 2lb 8oz and 9lb more over six months than those on low fat alternatives.

However, they should not exceed this time period as long-term effects are unknown.

Despite its endorsement from a range of A-list celebrities - including Gwyneth Paltrow and Jennifer Aniston - there are fears a high-protein diet can be dangerous.

Dr Heather Fields, of the Mayo Clinic in Arizona, said: "The best conclusion to draw is adhering to a short-term low-carb diet appears to be safe and may be associated with weight reduction.

"However that weight loss is small and of questionable clinical significance in comparison to low-fat diets.

"We encourage patients to eat real food and avoid highly processed foods, especially processed meats, such as bacon, sausage, deli meats, hot dogs, and ham when following any particular diet."

Her study analysed over a decade of research from January 2005 to April 2016 looking for possible adverse effects and overall safety.

Diets that heavily restrict carbohydrates often lead to greater consumption of meats - some of which have been implicated in raising the risk of cancer and premature deaths from other causes.

Meat-based diets have been found to increase the chance of heart failure in those aged over 50.

The Atkins diet advises followers to cut out carbohydrates for two weeks. It was followed by an estimated three million people in Britain at the height of its popularity when it took off in the late 1990s.

But previous research has found it increases the risk of constipation - a key factor in causing bowel cancer.

Dr Fields added limitations in the previous research made it difficult to draw broad conclusions.

For example, studies did not address the type of weight lost - whether muscle, water or fat. They also primarily relied on dietary recall which is highly susceptible to error.

Dr Tiffany Lowe-Payne, a family doctor in North Carolina, said: "Factors like the patient's genetics and personal history should be considered along with the diet programs they've tried before and, most importantly, their ability to stick to them."

She acknowledged carbohydrates are a mainstay of most people's diets and, after six months, weight loss is virtually the same as for people on a low-fat diet.

She added low-carb diets deliver early benefits for patients trying to lower their blood sugar levels or manage insulin resistance.

Dr Lowe-Payne said: "When you think of what dieters want - and what they need to stay motivated - it's the satisfaction of results.

"They want to see significant weight loss and fast. For many a low-carb lifestyle provides the answer they are looking for."

The study was published in The Journal of the American Osteopathic Association.