Low-Carbohydrate Diets Promote Weight Loss

The controversial low-carbohydrate, high-fat diet advocated by the late Dr. Robert Atkins is more effective than a low-fat, calorie-restricted diet for promoting weight loss, according to two separate reports in the New England Journal of Medicine (2003;348:2074–81 and 2003;348:2082–90). Moreover, people who followed the Atkins diet, which emphasizes foods such as steak, butter, eggs, and cream, showed improvements in certain heart-disease risk factors, including triglycerides, high density lipoprotein (HDL, "good") cholesterol, and insulin sensitivity.

Atkins' diet books have sold more copies than any other nutrition book in history. His low-carbohydrate approach goes against conventional medical opinion, which holds that the best way to lose weight and improve cardiac risk factors is to consume a low-fat, low-calorie diet. Atkins has pointed out that severely restricting one's carbohydrate intake leads to changes in the body's metabolism (ketosis) which cause calories to be lost in the urine in the form of ketones. Most doctors and scientists, however, are not convinced that ketosis can promote any worthwhile degree of weight loss, nor that loading up on dietary fat is safe.

In the new studies, middle-aged obese men and women were randomly assigned to consume a very low-carbohydrate diet (as advocated by Atkins), with no calorie restrictions, or a low-fat diet that limited the total amount of calories consumed per day. In one of the studies, during the first three months, those assigned to the Atkins diet lost an average of 6.8% of their body weight, compared with a 2.7% loss in the low-fat diet group. Similar results were seen after 6 months. After 12 months, however, participants in both groups had regained a portion of the weight they had lost, and while the total amount of weight loss was still greater in the Atkins group, the difference was no longer statistically significant. In the other study, which lasted only 6 months, the average amount of weight loss was significantly greater in the low-carbohydrate group than in the low-fat group (12.8 vs. 4.2 pounds).

Compared with the low-fat diet, the low-carbohydrate diet resulted in significant improvements in levels of triglycerides and HDL cholesterol, and in insulin sensitivity. Each of these improvements would be expected to reduce the risk of heart disease.

The results of these studies are weakened by the high dropout rate (40% in both studies) and by the fact that some participants adhered poorly to the dietary recommendations. In addition, the weight gain that occurred during the second six months in one of the studies raises questions about the long-term effectiveness of the Atkins diet. Nevertheless, both studies support Atkins' claim that motivated individuals can successfully lose weight by restricting their carbohydrate intake.

Despite the apparent benefits of a low-carbohydrate diet for people who have difficult losing weight, it is not without risk. An earlier study suggested that long-term carbohydrate restriction might increase the risk of osteoporosis. Furthermore, although it does improve certain cardiac risk factors, a low-carbohydrate diet limits the intake of a wide range of plant-derived chemicals, such as flavonoids, carotenoids, and antioxidants, that may help prevent heart disease, cancer, and other disorders. Those who have difficulty accepting the notion that loading up on bacon, butter, and steaks could be good for you can take comfort in the fact that the final word is not yet in.

Alan R. Gaby, MD, an expert in nutritional therapies, testified to the White House Commission on CAM upon request in December 2001. Dr. Gaby served as a member of the Ad-Hoc Advisory Panel of the National Institutes of Health Office of Alternative Medicine. He is the author of Preventing and Reversing Osteoporosis (Prima, 1994), and co-author of The Natural Pharmacy, 2nd Edition (Healthnotes, Prima, 1999), the A–Z Guide to Drug-Herb-Vitamin Interactions (Healthnotes, Prima, 1999), Clinical Essentials Volume 1 and 2 (Healthnotes, 2000), and The Patient’s Book of Natural Healing (Prima, 1999). A former professor at Bastyr University of Natural Health Sciences, in Kenmore, WA, where he served as the Endowed Professor of Nutrition, Dr. Gaby is the Chief Medical Editor for Healthnotes, Inc.

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