Tuesday, May 18, 2004

Low-Carb Diet Performs in Clinic
By Mike Upchurch

The carb-cutting craze received some strong scientific support in the form of a Duke Medical Center study this week. Duke doctors report that a low-carb, high-protein diet was better at shedding pounds and dangerous forms of cholesterol than a low-calorie, low-fat diet. But they caution that the long-term effects of drastically cutting carbohydrates are still unknown.

William Yancy, MD

"This diet can be quite powerful," said lead researcher Will Yancy, M.D., an assistant professor of medicine at Duke University Medical Center and a research associate at the Veterans Affairs Medical Center in Durham, NC. "We found that the low-carb diet was more effective for weight loss."

Yancy added, "The weight loss surprised me, to be honest with you. We also found cholesterol levels seemed to improve more on a low-carb diet compared with a low-fat diet."

Writing in the May 18 issue of the Annals of Internal Medicine, Dr. Yancy and his colleagues reported that dieters on the Atkins-style, low-carb plan lost an average of 26 pounds, compared with 14 pounds for those on the low-fat, low-calorie diet. Though the low-fat eaters reduced their overall cholesterol more than the carb cutters, the low-carb diet produced a much larger reduction in body fat and in triglycerides, a harmful fat related to cholesterol found in the bloodstream.

Patients who lowered their carbs saw their triglycerides cut in half and a 5-point boost in their HDL, or “good” cholesterol. Despite higher rates of adverse effects such as constipation and headaches, fewer carb watchers dropped out of the program than the low-fat dieters.

But Yancy still does not recommend the diet for those trying to lose weight for the first time, and he is wary of the long-term effects on the body.

“Over 6 months, the diet appears relatively safe, but we need to study the safety for longer durations," Yancy said. Extremely low-carb diets could increase LDL, or “bad” cholesterol, levels, as well as lower bone density and increase the risk of kidney stones, according to Yancy.

The 120 study participants were randomized to either the low-carbohydrate, high-protein diet or the low-fat, low-cholesterol, low-calorie diet. All were aged 18 to 65 years and in generally good health, but were clinically obese and had a total cholesterol level of more than 200 mg/dL. None had tried dieting or weight loss pills in the previous 6 months.

The low-carbohydrate group was permitted daily unlimited amounts of meat, including fish and shellfish, unlimited eggs, 4 ounces of hard cheese, 2 cups of salad vegetables such as salad or spinach, and 1 cup of low-carbohydrate vegetables such as broccoli, cauliflower or squash. They also received daily nutritional supplements including a multivitamin, essential oils and chromium picolinate, a trace mineral that helps metabolize fats and carbs. There were no restrictions on total calories, but carbohydrates were kept below 20 grams per day at the start of the diet.

The low-fat, low-cholesterol, low-calorie diet consisted of less than 30% of daily caloric intake from fat, less than 10% of calories from saturated fat, and less than 300 mg of cholesterol daily. Those on this diet were also advised to cut back on calories. The recommended daily calorie level was 500 to 1000 calories less than what the dieter needed to maintain his or her current weight.

Though the study was funded by the Robert C. Atkins Foundation, no one on Dr. Yancy’s team has any financial stake in the Atkins nutritional empire. The researchers retained full control of the study data and analyses at all times.

Dr. Yancy was joined by Maren Olsen, PhD; John Guyton, MD; Ronna Bakst, RD; and Eric Westman, MD, who was co-principal investigator.