LONDON -- A look at all the research on the diet is revealing the good and bad effects of the popular high-fat, low-carb Atkins diet.

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A report in this week's issue of the journal Lancet says that low-carbohydrate diets have been around since the 1860s, but the Atkins books are the most successful to date, with more than 45 million copies sold.

The Atkins diet approach allows unlimited consumption of protein and fat but severely limits carbohydrates.

When Frank Long, 41, stuck to his Atkins-type diet for a year, he shed 95 pounds.

"Actually, I haven't felt better since I was in my 20s," he said.

The new study found that dieters on the Atkins approach lose just as much body fat as those on low-fat diets.

At six months, Atkins dieters lost as much body fat as those on low-calorie, low-fat diets. And in the short term they lost more weight and some had better cholesterol improvement. But after a year, the two types of dieters had about the same weight loss.

The review of 60 studies also found that Atkins dieters may also experience such annoying side effects as headaches, muscle weakness and constipation more than people following more conventional diets.

Danish obesity expert Dr. Arnt Astrup, who conducted the review, said the irritating discomforts associated with Atkins-type diets may be signs that low-carb diets aren't healthy in the long run.

Not everyone agrees with his findings. Several experts say the side effects aren't bad enough to force people from low-carb diets that shun bread, pasta and many fruits.

Seattle weight loss specialist Dr. Robert Kanter said the findings show the Atkins diet is safe for some, reported KIRO-TV in Seattle.

"For use over six months, there does not appear to be any adverse effect on the heart or on people's general health if they don't have osteoporosis, kidney stones or diabetic kidney disease," Kanter said.

But he said the new research reinforced that weight loss comes down to calories.

"It didn't matter what the carbohydrate content was. What was critical was how long they stayed on the diet and how much they restricted their calories," he said.

No one knows yet the very long-term health effects of the Atkins diet. Astrup said longer-term studies are needed to determine the diet's safety and effectiveness.