People trying to lose weight by following the so-called "Atkin's diet", which restricts carbohydrate but not fat or protein intake could cut their chance of getting heart disease, suggests a new US study.

Overweight subjects on the high-fat, high-protein diet - which allows butter, mayonnaise and steak - increased the proportion of "good" cholesterol and cut the level of fatty triglycerides in their blood compared with those on conventional low fat, high carbohydrate diets.

Importantly, the protein and fat-laden diet did no harm, with no increases in levels of "bad" cholesterol. In fact, subjects on the Atkin's diet also lost more weight, although this did not remain statistically significant after a year.

"Obesity is a national public health problem, and we need to evaluate alternative weight loss approaches aggressively. Widely recommending low carbohydrate approaches may be premature, but our initial findings suggest that such diets may not have the adverse effects that were anticipated," says Gary Foster, the lead researcher and clinical director of the Weight and Eating Disorders Program at the University of Pennsylvania.

The results were "unexpected", Foster told New Scientist. This is the first controlled trial of the Atkin's diet, and the "common sense notion that it would be associated with increases in bad cholesterol" was expected to prevail.

Although Foster cautions against recommending the diet, he says further work may endorse it as a useful option for weight loss.

More filling

The Atkin's diet, devised by US doctor Robert Atkins, raised levels of HDL cholesterol, known as good cholesterol, by an average of 11 per cent compared with only 1.6 per cent in conventional dieters after one year.

Fatty triglycerides were slashed by 17 per cent after one year on the Atkin's diet compared with no significant change in people on the high carbohydrate diet.

Weight loss was also statistically greater in Atkin's dieters after three and six months compared with conventional dieters, in the study of 63 obese men and women.

The team do not know how the Atkin's diet worked to produce these effects. "There is some evidence that food high in protein may be more filling," says Foster. This may make it easier for people to eat fewer calories. "Even when you tell people they can eat everything they want, they just don¹t want to."

He adds the other reason might be that the Atkin's diet adds more structure to eating than a conventional diet as there are definite foods which can and cannot be eaten.

The diet prescribes limits for only carbohydrate intake - this includes fruit, vegetables, bread and pasta. Under a high-carbohydrate diet an average man eating about 2000 calories a day may have a daily carbohydrate intake of 300 grams, says Foster. Under the Atkin's diet this would be restricted to as little as 20 grams per day for the first two weeks, increasing slowly on a set scale depending on the amount of weight lost.

The team is now starting a five-year study to assess the risks and benefits of the diet in detail.

Journal reference: New England Journal of Medicine: (vol 348, p 2082)


Shaoni Bhattacharya