Atkins diet's long-term effects are unclear
HARVARD MEDICAL SCHOOL ADVISER
October 6, 2003
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My doctor advised me against trying the Atkins diet. Her explanation made sense, but then I read three magazine articles saying that the diet works and isn't dangerous. What's the story?
The Atkins diet is a high-fat, low-carbohydrate eating plan. Rather than count calories, it counts carbohydrates ("carbs"). The theory is that carbohydrates (sugars and starches) raise insulin levels and cause other metabolic changes that lead to weight gain.
The Atkins diet defies mainstream nutrition advice in two key ways. First, it allows dieters to eat high-fat foods - including those high in saturated fat (steak, cheese, bacon). High intake of saturated fat is linked to heart disease and other health problems.
Second, it eliminates nearly all carbohydrates. Dieters cut out not only sweets and snacks, but also many fruits, vegetables and grains.
This goes against scientific evidence showing the health benefits of these foods.
Despite these faults, studies suggest that the Atkins diet may be effective at achieving short-term weight loss.
Here is a summary of some the studies. In a study funded by the Atkins Foundation, Duke University Medical Center researchers compared the Atkins diet to the low-fat, low-calorie diet. After six months, the Atkins dieters had lost more weight and, remarkably, had better cholesterol readings than those on a conventional diet.
In another six-month study, not supported by the Atkins Foundation, a University of Cincinnati team found that Atkins dieters lost more weight and more body fat than the low-fat, low-calorie dieters, corroborating at least part of the Duke study. But, unlike that study, the cholesterol readings of the two groups were about the same.
Researchers at the Philadelphia Veterans Affairs Medical Center compared the effects of a low-carbohydrate diet with those of a low-calorie diet. In their study, which included only very overweight individuals - people on the low-carbohydrate diet lost more weight over six months than did those on a low-calorie, low-fat diet.
Finally, another small, one-year study looked at the effect of the Atkins diet on weight loss and heart disease risk factors in obese people. After six months, Atkins dieters had lost a little more weight than the conventional dieters had.
However, after one year, the two groups had lost about the same number of pounds.
The low-carbohydrate dieters had greater improvement in certain heart disease risk factors - HDL ("good") cholesterol levels went up, and triglycerides went down.
If these studies are right, and the Atkins diet can help many people achieve short-term weight loss, how does it work?
One theory is that, calorie-for-calorie, fat is better than carbohydrates at controlling appetite. A 2001 Harvard study supports this idea. After 18 months, individuals on a moderate-fat diet (which emphasized "healthy fats," not saturated fats) had lost an average of about nine pounds.
Low-fat dieters actually gained, on average, about six pounds because they couldn't stick with the program.
Because none of these trials lasted very long, they can't tell us about the long-term effects of this diet. Also, the studies involved small numbers of people, so it is hard to know whether the results were due to the diet, or occurred by chance.
Only larger, longer studies can determine the potential risks and benefits of a low-carb, high-fat diet. But the recent results are food for thought.
Also, data from the Nurses' Health Study indicate high-protein diets may decrease the risk of heart disease.
If you are overweight, losing weight and keeping it off is healthy. You do not improve your health by losing and regaining weight repeatedly ("yo-yo dieting"). We think the latest studies provide evidence that the Atkins diet can help people lose weight in the short-term - but not over the long haul.
What about people who keep weight off by staying on the Atkins diet indefinitely? For them, we still don't know whether the bad aspects of the Atkins diet - the high intake of saturated fats and the low intake of fruits and vegetables - might cancel out or even reverse the benefits of lasting weight loss.
The Harvard Medical School Adviser is researched and written by the faculty and staff of the Harvard Medical School. You can E-mail questions to the Harvard Medical School Adviser at Harvard_Adviser~hms.harvard.edu.
"Atkins diet's long-term effects are unclear"
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