Low Carbohydrate versus High Carbohydrate Diet Compositions

A recent article in the May 22nd, 2003 edition of the New England Journal of Medicine highlights the continued debate between low carbohydrate and high carbohydrate diet supporters.  A total of 63 obese (BMI greater than 35) men and women participated in this study, which took place in the eastern United States of America.  They were randomly assigned to eat either a low carbohydrate, high protein and high-fat diet (ie. the Atkins diet) or high carbohydrate, low-fat diet for one full year.  The amount of weight loss and the changes in cholesterol, triglycerides and insulin resistance were then measured.

The results hit the national press the day before publication because of one main conclusion from this low-powered study: participants eating the Atkins-style diet lost more weight in the first six months than did those eating a high carbohydrate diet.  This juicy tidbit has already spread like wildfire among those who wish to condone their typical western eating habits: fast foods, pre-prepared packaged foods, high fat, low carbohydrate, etc.

But wait a minute.  Let’s analyze this study a bit more carefully!

The media broadcasts failed to point out that although weight loss appeared to be more rapid in the Atkins-style dieters, this was true for only the first six months; at twelve months of follow-up, the high carbohydrate eaters had caught up.  Another very important point to note is that the diet compositions were not really that terribly different!  The percentage of fat in the Atkins-style diet was roughly 41%, whereas the percentage of fat in the high carbohydrate diet was still much higher than the ideal, tallying a whopping 33%.  The crucial issue is that the diets in truth were really not all that different (compare the CHIP ideal percentage of fat, which is less than 20% of total calories consumed).  The authors of the study themselves concluded that the reason for the more rapid weight loss with the Atkins-style diet was that this group had actually consumed considerably less total calories per day than did the high carbohydrate group; thus, the supposedly impressive result was due to calorie restriction, and NOT the specific fat/protein/carbohydrate composition of the two diets.  Sadly, this is not what the general public will conclude from the media coverage of this study!

One final point, in case the take-home message is not yet clear: this study does NOT prove the superiority of a high protein, high fat, low carbohydrate diet over a high carbohydrate, low-fat diet.  In fact, it doesn’t prove anything other than: the more you restrict your calories, the faster you’ll lose more weight?!

Christine Simpson, MD ?Chip Director, Edmonton, AB