One of the largest studies to date has found that overweight women lost a little more weight on the popular Atkins diet than on three other well-known diet plans. However, the effect was small, and it is not clear that the Atkins diet works the way it claims.
The 1998 Atkins diet, which calls for replacing “carbs” (carbohydrates, starch and sugar) with fat and protein, has been among the most popular “miracle” diets.
Christopher Gardner and colleagues at Stanford University in California, US, put 311 overweight women between 20 and 50 years old on either Atkins, or one of three other popular diets:
- Zone, which cuts carbs less severely than Atkins
- LEARN, a low-fat, high-carb diet based on US national guidelines
- Ornish, an extreme low-fat plan
After a year, all the women had lost some weight. The Atkins group lost more on average than the groups on all other diets – 4.7 kilograms (10.3 pounds) versus 1.6 kg (3.5 lbs) for Zone, 2.6 kg (5.7 lbs) for LEARN and 2.2 kg (4.8 lbs) for Ornish. However, only the difference between the Atkins and Zone groups was statistically significant.
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Underlying mechanisms
There are fears that the increased fat consumed with the Atkins diet could lead to cardiovascular problems. In this study, however, the Atkins group had the best “good” cholesterol, blood triglycerides (fat), and blood pressure. “Apparently the predicted adverse effect of more saturated fat in the diet is counterbalanced by losing even just slightly more weight,” Gardner told New Scientist.
It is less clear, though, how the weight is actually lost. “Was the slight benefit on Atkins due to the low carbs, or the high protein, or the eight glasses of water a day which may have replaced sweetened beverages?” asks Gardner. “We don’t know.”
Atkins claims that changing the ratio of carbohydrate and fat in the diet changes a person’s fat-storage metabolism. But, says Gardner, the diet may just make it easier to eat fewer calories from any source, possibly because most modern caloric excess comes from carbohydrates.
Less is more
Arne Astrup at the University of Copenhagen also suspects the advantage of Atkins may simply be fewer calories, not a changed metabolism. This is because eating more protein fills you up more per calorie, so you eat less. But he says more tightly controlled studies are needed to resolve the question.
Other studies comparing diets, he notes, have found no significant difference between them and even opposite results for the same diet in some cases. Astrup thinks this is probably because people rarely stick to these diets.
“After one year no-one was sticking very closely to any of the plans,” agrees Gardner, who says his aim was test the actual, real-world use of diet books. He adds that while some books can help achieve short-term weight loss, the real test of weight loss is keeping it off.
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