Low-Carb Diet Research and News

Duke Health Briefs: Low-Carb Diet Effective In Research Study

DURHAM, N.C. – The high-protein, low-carbohydrate diet popularized by Dr. Robert Atkins has been the subject of heated debate in medical circles for three decades. Now, preliminary research findings at Duke University Medical Center show that a low-carbohydrate diet can indeed lead to significant and sustained weight loss.

There has recently been a resurgence of diets promoting low carbohydrate intake, but the scientific evidence supporting the safety and effectiveness of these diets is limited. This is the first published scientific study of the popular low-carbohydrate Atkins diet in two decades, and research is continuing.

The study appears in the July 2002 issue of the American Journal of Medicine and was funded by an unrestricted grant from the Atkins Center for Complementary Medicine.

“Study participants were put on a very low carbohydrate diet of 25 grams per day for six months,” said Eric Westman, M.D., associate professor of medicine at Duke and principal investigator of the study. “They could eat an unlimited amount of meat and eggs, as well as two cups of salad and one cup of low-carbohydrate vegetables such as broccoli and cauliflower a day.”
Researchers found that 80 percent of the 50 enrolled patients adhered to the diet program for the duration of the study and lost an average of 10 percent of their original body weight. The average amount of weight lost per person was approximately 20 pounds.

“While we’re impressed with the weight loss of this diet, we still are not sure about the safety of it,” Westman said. “More studies need to be done in order to be confident about the long-term safety of this type of diet.”

For example, all participants developed ketonuria, the presence of measurable ketones in urine. The level seen in this study translates to roughly that of a non-dieting person if they didn’t eat for a couple of days, said Westman. “This is a finding that we need to learn more about. The level of ketones present was not terribly high, but we don’t know if this is safe or harmful to one’s health over a long period of time.”

The study further showed that patients’ cholesterol levels improved by the end of six months -- a finding that was unexpected, according to Westman.

“We were somewhat surprised to find that patients’ blood lipid profiles improved, even though there was much more fat in the diet,” he said. “We had thought the fat in the diet would increase the cholesterol.”

Cholesterol is a fat-like substance that circulates in the blood stream and can accumulate to the point of blocking blood vessels and arteries. Having a high level of blood cholesterol is a major risk factor for heart disease, according to the National Heart Lung and Blood Institute, part of the National Institutes of Health.
Although exercise was recommended, it was not a requirement for the study. Half of the subjects didn't exercise at all and still lost weight, according to the researchers.

Because of the intensity of this type of diet program, Westman cautions that “if someone has a medical problem or is taking medications, they should only do this diet under the supervision of a health care provider."

Abstract:

Am J Med 2002 Jul;113(1):30-6 Related Articles, Books, LinkOut

Effect of 6-month adherence to a very low carbohydrate diet program.

Westman EC, Yancy WS, Edman JS, Tomlin KF, Perkins CE.

Division of General Internal Medicine, Duke University, 2200 West Main Street, Durham, NC 27705, USA. ewestman~duke.edu

To determine the effect of a 6-month very low carbohydrate diet program on body weight and other metabolic parameters. Fifty-one overweight or obese healthy volunteers who wanted to lose weight were placed on a very low carbohydrate diet (<25 g/d), with no limit on caloric intake. They also received nutritional supplementation and recommendations about exercise, and attended group meetings at a research clinic. The outcomes were body weight, body mass index, percentage of body fat (estimated by skinfold thickness), serum chemistry and lipid values, 24-hour urine measurements, and subjective adverse effects. Forty-one (80%) of the 51 subjects attended visits through 6 months. In these subjects, the mean (+/- SD) body weight decreased 10.3% +/- 5.9% (P <0.001) from baseline to 6 months (body weight reduction of 9.0 +/- 5.3 kg and body mass index reduction of 3.2 +/- 1.9 kg/m(2)). The mean percentage of body weight that was fat decreased 2.9% +/- 3.2% from baseline to 6 months (P <0.001). The mean serum bicarbonate level decreased 2 +/- 2.4 mmol/L (P <0.001) and blood urea nitrogen level increased 2 +/- 4 mg/dL (P <0.001). Serum total cholesterol level decreased 11 +/- 26 mg/dL (P = 0.006), low-density lipoprotein cholesterol level decreased 10 +/- 25 mg/dL (P = 0.01), triglyceride level decreased 56 +/- 45 mg/dL (P <0.001), high-density lipoprotein (HDL) cholesterol level increased 10 +/- 8 mg/dL (P <0.001), and the cholesterol/HDL cholesterol ratio decreased 0.9 +/- 0.6 units (P <0.001). There were no serious adverse effects , but the possibility of adverse effects in the 10 subjects who did not adhere to the program cannot be eliminated. A very low carbohydrate diet program led to sustained weight loss during a 6-month period . Further controlled research is warranted