Low-Carb Diets

Low-carb diets: Research is inconclusive

Our research uncovered both advocates and detractors for low-carbohydrate (low-carb) diets such as the Atkins diet and, to a lesser degree, the South Beach and Zone diets. The best research can be found on the website of the Obesity Society, where editors summarize nearly every major scientific study of low-carb diets (including Atkins) from the 1970s onward. In a format that's slightly easier to digest, the Journal of the American Medical Association has a 2007 comparative study of Atkins, Dean Ornish, the Zone and LEARN diets, and another 2005 comparative study of Weight Watchers, Atkins, Dean Ornish and the Zone diets, while the New England Journal of Medicine has an in-depth one-year study of Atkins and the recently published "Weight Loss with a Low Carbohydrate, Mediterranean, or Low-Fat Diet."

Ultimately, the scientific community is split on low-carb weight-loss programs. Vehement detractors include the American Heart Association, which expresses concerns that a diet high in protein and fat and low in nutrient-rich fruits and vegetables can contribute to osteoporosis, heart disease, kidney stones, liver problems and diabetes. Dr. Dean Ornish, who has his own diet plan, also continues to insist that low fat is crucial to lowering overall cholesterol, though the New England Journal of Medicine study would indicate otherwise. Atkins proponents, however, assert that their diet is healthy, and studies do show that low-carb diets can help lower cholesterol. In the latest 2007 American Medical Association study, Atkins dieters lost the most weight, and secondary outcomes, like lipid profiles, triglycerides and blood pressure, were comparable to or more favorable with Atkins than the other diet groups, including Ornish's diet plan. This was bolstered by a 2008 New England Journal of Medicine study where a low-carb diet plan was found to be more effective for weight loss and reducing risk factors for cardiovascular disease than the low-fat plan.

Whether or not Atkins is the answer, there's evidence that the tide is turning in favor of reducing overall consumption of carbohydrates. The USDA 2005 food pyramid guidelines include a more favorable view of healthy fats, like those found in olive oil and fish. The pyramid also encourages reducing refined carbohydrates, such as white bread and pasta, in favor of whole grains -- the net effect to the body is fewer carbohydrates. It will be interesting to see what the 2010 USDA pyramid looks like in light of the New England Journal of Medicine and Nutrition Journal studies that show low-carb and Mediterranean plans to be not only a viable alternative, but potentially more effective for weight loss and reducing cardiovascular-disease risk factors than a low-fat diet. According to researchers who conducted clinical trials at the American Heart Association, substituting protein (half from plant-based sources) or monounsaturated fats for even 10 percent of dietary carbs can reduce the chances for heart disease.

Mediterranean diets are getting a closer look of late. In the New England Journal of Medicine's study, women following a Mediterranean diet lost more weight than on a low-carb or low-fat plan. (Men lost more on a low-carb plan.) And all participants following the Mediterranean plan lowered their cardiovascular disease risk factors. Mediterranean diets are low in refined carbohydrates, rich in unsaturated fats, seafood and vegetables. Olive oil and sometimes red wine are integral parts of the diet. Harvard Medical School's "Eat, Drink, Be Healthy" outlines the tenets of a Mediterranean plan though there are plenty of variations out there, such as The Sonoma Diet (*est.$25 for the book) and more esoteric Spanish Ketogenic Mediterranean Diet (SKMD). Nutrition Journal reported on a small, 31-person, 12-week study of the SKMD, which yielded promising results; eating an unlimited-calorie diet rich in olive oil, salad, fish and red wine, subjects lost weight and lowered their blood pressure, cholesterol and glucose. The authors recommend longer study in the future as well as comparison between the SKMD and other low-carb weight-loss programs.

Diets based on regulating blood glucose and eating foods with a lower glycemic index are also gaining credibility. The New Glucose Revolution (*est. $17 for the book) was among the top three plans reviewed by the American Dietetic Association's study comparing dietary quality of several popular plans. It's also among the top-rated plans on Healthy Weight Forum. The science behind low-glycemic diets has to do with the impact of certain foods on your blood-glucose levels. Unrefined carbohydrates for example, cause blood sugar to spike temporarily, producing a high followed by a low, and ultimately a craving for more. Foods that don't cause that spike in blood sugar, like leafy greens, lean protein and healthful fats, will keep you satisfied longer, reducing overall food consumption.

Two diets that have faded from the limelight are the South Beach and Zone. In their place, Volumetrics, The Abs Diet and Burn the Fat, Feed the Muscle have emerged as popular diet contenders. Volumetrics, the top pick by a leading consumer testing organization, is based on the book The Volumetrics Eating Plan (*est. $16 for the book). The Volumetrics plan focuses on foods that are filling but low in "energy density," allowing people to eat large quantities while still losing weight. Burn the Fat, Feed the Muscle (*est. $40 for downloadable e-book) and The Abs Diet (*est. $16 for the book) focus on exercise and strength training as central components of weight loss. Both are targeted toward men, but Burn the Fat, Feed the Muscle offers more advice on healthy living, meal plans and training tips according to the editors at FreeDieting.com.