Saturday, July 19, 2008

Is the Tide Turning?

See that logo? The New England Journal of Medicine is one of the premier scientific journals in the world. It is in the top tier of the top tier of medical journals.

Contrary to popular opinion, it is possible to get mediocre research published. You can present a preliminary poster of your findings at a scientific meeting and it will appear in a volume summarizing all the posters from that meeting. You can submit your manuscript to a journal that will simply print it for you without any pesky review by your scientific peers.

But if you want credibility for your work, you send it to a respected journal where two or more qualified scientists will analyze it, tear it apart and ask you many questions about how you can back up your claims. The more respected the journal, the more likely that your submission will not pass muster and will be returned to you for submission elsewhere. In the scientific world, it's not just "publish or perish." The quality of the journals in which you publish is also extremely important.

For that reason, it is very significant that on July 17, 2008, the New England Journal of Medicine published an article entitled Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet. The study enrolled 322 Israelis (men and women, average age 52, diabetic and non-diabetic) who worked at a nuclear research facility and were moderately obese. They were divided into three groups.

The Low-Fat group adhered to the guidelines of the American Heart Association (AHA). They ate 30% fat, and were permitted very little saturated fat and cholesterol. Men were limited to 1800 calories per day and women were limited to 1500 calories per day.

The Mediterranean Diet group ate 35% fat, mostly in the form of olive oil. They ate lots of vegetables and were instructed to get their protein from chicken and fish. Men were limited to 1800 calories per day and women were limited to 1500 calories per day.

The Low-Carbohydrate group ate 20 grams of carbohydrates per day for two months, followed by a gradual increase to a maximum of 120 grams of carbs per day. Participants were told to choose vegetarian sources of fat and protein. Daily calories were not limited.

The results were not unequivocally in favor of the Low-Carb group. They had the poorest long-term adherence rate to their diet (78%). Their fasting plasma glucose levels did not improve. Their blood pressure, LDL cholesterol, insulin and leptin levels and high molecular weight adiponectin all improved, but there was no significant difference in the degree of improvement among the three diet groups.

Compared with the other two groups, the Low-Carb group did see a significant drop in their weight, in their glycosylated hemoglobin, and in their ratio of total cholesterol to HDL cholesterol. In several other markers, the Low-Carb and the Mediterranean diet groups were not different from each other, but showed significant improvement over the group following the AHA-recommended Low-Fat diet.

One of the criticisms made against the low-carb diet is that it might not be safe or effective in the long term when compared with the standard American Heart Association low-fat diet. This study specifically addressed that question. It is notable that in the Discussion, the authors of this article state, "In this 2-year dietary-intervention study, we found that the Mediterranean and low-carbohydrate diets are effective alternatives to the low-fat diet for weight loss and appear to be just as safe as the low-fat diet." The wobble you just felt was the tide turning.

This study has received wide publicity in print and on television. It is possible that, at long last, the medical community and the media are beginning to question the dogma that the only healthy diet is a low-fat diet.

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