An overview on low-carbohydrate diets

Atkins Nutritionals, Inc.Sep 7 2010

Headlines make news, but don't read too much into current headlines about a recent study titled "Low-Carbohydrate Diets and All-Cause and Cause-Specific Mortality," published in the September 7, 2010, issue of Annals of Internal Medicine. Although the headlines may say the study suggests that long-term adherence to a low-carb diet based heavily on animal protein may reduce lifespan, Dr. Funga, who was the lead author of the study, says that her research "is not representative of popular low-carb eating plans." She goes on to note that her study "is observational and based on a limited pool of health professionals rather than a large-scale, clinical trial based on a varied population. Other issues in the design of the study, such as depending on food frequency questionnaires, impact its conclusions." So why all the fuss? Headlines make news but headlines can be misleading; and that's why Atkins wants to clarify study conclusions and correct any misperception.

• The "Low-Carb" Diet Is Not Representative of Atkins. The so-called "low-carb" diet referenced in Dr. Funga's research is not representative of Atkins. In the journal's editorial, Drs. Yancy, Maciejewski, and Schulman, of Duke University Medical Center commented on Dr. Funga's study. They wrote, "The participants in the highest decile of low-carbohydrate diet score (that is, those eating the least amount of carbohydrate) actually had a moderately high carbohydrate intake."
• The Protocol Is Not Atkins. Dr. Jeffrey Volek, associate professor at the University of Connecticut, notes that, "In respect to the Atkins Diet, it should be emphasized that using these data as an indictment of the diet as being unhealthy is inappropriate. From the data presented, the cohort with the lowest carbohydrate intake had a median carbohydrate intake (percentage of energy) of 35 percent for men and 37 percent for women. This is nowhere close to the level of carbohydrate restriction in any phase of the Atkins Diet."
• Low-Carb Diets Work. Major clinical research has demonstrated the health benefits of low-carb diets. Dr. Eric Westman, also of Duke University Medical Center, noted that, "The randomized controlled trials have repeatedly sided with, not against, low-carbohydrate diets. The latest study, published in Circulation 2010 by Dr. Shai and colleagues, showed that the low-carbohydrate diet (with animal sources of protein) led to reduction in carotid artery thickness over a two year period."
  • As the editorial authors stated, several clinical trials in the past 10 years have demonstrated that a low-carbohydrate, high-fat, high-protein diet is at least as effective as a calorie-restricted, high carbohydrate, low-fat diet for weight loss and improvement of heart health risk factors. A recently published study of two years duration found that a low-carbohydrate diet had better HDL ("good") cholesterol and triglyceride results than did a low-fat diet.
• Current Study Limitations. According to Dr. Westman, "This study is observational so it measures associations and cannot prove causation. Moreover, the association found was extremely weak." Dr. Volek added, "What strikes me about this study is the assumption by the authors that that a massive number of subjects overcomes the well known limitations associated with using food frequency questionnaires (FFQ).  Even if we assume some level of accuracy in assessing carbohydrate and overall nutrient intake by FFQ, the authors only examined food intake once: at the start of the 20-plus-year study. If a person changed his diet at any point during the two-decade study it would not be reflected in the analysis."
• Atkins also takes issue with how the study determined which low-carb diets were vegetable-protein based and which were animal-protein based. As noted by the journal's editorial authors, "It turns out that participants in the highest decile of the vegetable score consumed similar amounts of fat and protein from animal sources as did participants in the upper deciles of the animal source." Continued the editorial authors, "Despite lay press representation to the contrary, low-carbohydrate diets are fairly rich in vegetables, particularly after the early restrictive phase of these diets." This is evident in the Atkins approach which emphasizes the consumption of low-glycemic fruits and vegetables and vegetarian proteins such as tofu, in addition to animal proteins.

The Bottom Line

Dr. Funga's work may be thought provoking and newsworthy, but she acknowledges that nothing in her research takes away from recent clinical research and findings about the health benefits associated with low-carb diets. She acknowledges many of the weaknesses and limitations associated with long-term observational studies, and the difficulties conducting them. In the last ten years, peer-reviewed journals have published more than 60 studies investigating low-carb diets, many of them based on Atkins protocols. All demonstrate positive results in terms of weight loss, as well as improvements in lipid profiles, reduced inflammation and better blood sugar control. In contrast, a single study, with significant limitations, suggests caution about the sources of protein.