High-fat, low-carb diets like Atkins may help people lose weight, but its side effects could lead to problems in the long term, a new review suggests.

Prof. Arne Astrup, an obesity researcher in Denmark, analyzed three studies on the longer-term effects of low-carb diets. The studies put volunteers on either a low-carb diet or a low-calorie, low-fat diet.

More than 45 million copies of the books have been sold.
More than 45 million copies of the books have been sold.

The Atkins diet advocates eating unlimited amounts of protein and fat from butter, meat and dairy products while drastically reducing carbohydrates like grains and fruits in the initial stage.

The diet's inventor, U.S. doctor Robert Atkins, proposed if people are starved of carbohydrates and fed protein, their bodies will start to burn stored fat.




People on low-carbohydrate diets tend to lose more weight for the first six months, but after 12 months, the weight loss is similar to those on low-fat diets, Astrup concluded.

"There is no clear evidence that Atkins-style diets are better than any others for helping people to stay slim, and despite the popularity and apparent success of the Atkins diet, evidence in support of its use lags behind," the researchers wrote in Saturday's issue of The Lancet.

"Although the diet appears as claimed to promote weight loss without hunger, at least in the short term, the long-term effects on health and disease prevention are unknown."

Unpleasant side effects

Those who stayed on the Atkins diet for a year typically complained of constipation and headache, which can be explained by the lack of fruits, vegetables and whole grains, Astrup said.

Bad breath, muscle cramps, diarrhea, general weakness and rashes were also reported more frequently by low-carb dieters, compared to those on a low-fat diet, Astrup and his colleagues at RVA University in Copenhagen reported.

The team suggested low-carb dieters may lose weight because they're bored – the diet is so monotonous that people eat less.

Or, the protein may make dieters feel fuller compared to fat or carbohydrates, the researchers said.

The side effects could be caused by dehydration, said William Yancy, a Duke University researcher who conducted one of the major studies that Astrup reviewed.