Ever since Robert Atkins, MD, popularized his high-protein, high-fat, low-carbohydrate diet in the 1970s, the mainstream medical community has predicted disastrous consequences, from increased risk of colon cancer (because of low fiber) to heart disease. In the past year, however, surprising results of the first serious research efforts on the diet have trickled in, suggesting it brings about weight loss without apparent harm. But before you dive headlong into a juicy steak and béarnaise sauce, know that the findings are—at best—both preliminary and ambiguous. "My largest worry," says Gary Foster, PhD, who headed one of the most talked about studies, "is that the public will misinterpret this data as license to eat a high-saturated-fat diet." Researchers are holding out for the more definitive conclusions of a much larger, five-year National Institutes of Health study that is just getting off the ground and will monitor effects on cholesterol and bone, along with weight loss. Here's what scientists know today about the safety and effectiveness of the Atkins diet-and what they don't.
Faster Weight Loss?
Does the Atkins diet work better than the conventional low-fat route?

Studies so far: The longest study to date lasted only a year and was small—only 37 people completed the full 12 months, 20 of them on Atkins and the other 17 on a traditional low-fat regimen. The researchers found that those on the Atkins diet shed more pounds during the first six months, but by the end of the year there was no significant difference in the amount the two groups lost (about 13 pounds per person). Additional studies also showed faster results by those on Atkins-like diets, although much of the weight dropped in the first week or two is water.

But...there's nothing miraculous about eliminating carbs, says Dena Bravata, MD, a research scientist at Stanford University who did an analysis of low-carb diet studies. She maintains, like most experts, that losing weight is merely a matter of consuming fewer calories than you burn—and these diets help restrict calories. But one new pilot study from Harvard has just thrown a wrench into this accepted wisdom: When people on a low-fat regimen ate exactly the same number of calories as those on an Atkins-type diet, the latter group lost more weight. An additional low-carb group who ate 300 more calories per day still lost more than the low-fat dieters. Their study was very small (21 people) and lasted only 12 weeks, and the researchers can't explain the findings. But it opens the door to the heretical notion that not all calories are created equal. Stay tuned for further research.
Bad for Cholesterol?
For decades doctors have preached that eating too much saturated fat can lead to heart disease and obesity, and studies have consistently backed this up. So the biggest fear of many health professionals is that a diet of steak, eggs, and butter might increase the buildup of plaque in the arteries, which causes heart attacks and strokes. The limited number of short-term studies (the longest, a year) have not shown the Atkins diet to affect cholesterol adversely. But...again, the long-term effects are impossible to forecast. The authors of these studies and other experts in the field are quick to point out that any weight loss will cause a person's "bad" cholesterol levels to fall. They also caution that anyone trying this diet should reduce fat intake—especially saturated fat—once the maintenance phase begins; otherwise it's easy to regain what you lost and put yourself at increased risk of heart disease.
Dangerous for Kidneys and Bones?
Diets high in animal protein result in an acid overload that could lead to a higher risk of kidney stones and osteoporosis. Results of the only study to examine kidney function were striking. When subjects switched to Atkins from their regular diet, they excreted over 60 percent more calcium and their urine was markedly more acidic, placing them at higher risk of kidney stones. Shalini Reddy, MD, at University of Chicago, launched the study because, she says, "we had patients on the Atkins diet saying that they were getting kidney stones." However, during the eight-week study, Reddy and her colleagues could measure only risk factors, not actual kidney stones, which can take quite a while to form. As for osteoporosis, there are no long-term studies associating it with a low-carb diet. The NIH project will begin to address this concern.
Final Verdict
The Atkins diet seems to produce fast weight loss—perhaps even more effectively than low-fat regimens. But it gradually loses steam. More important, staying on this diet for longer than six months may pose serious health risks. Until science has the answers, you might try jump-starting your efforts with Atkins, but then ease into a lower-fat diet that's moderate on carbs, high in fiber, fruits, and vegetables, and proven safe over the long term.


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