A study recently published in the Archives of Internal Medicine has demonstrated that a low-carb diet is more effective at lowering blood pressure than the weight–loss drug orlistat in concert with a low-fat diet. William S. Yancy, Jr., an associate professor of medicine at Duke University Medical Center and the lead author of the study, answers our questions.
Atkins: Dr. Yancy, where was the study conducted and how was it set up?
Yancy: I’m a staff physician at the Veterans Administration Medical Center in Durham, North Carolina, where my team conducted the research, which lasted for a year and included 146 overweight participants. The Department of Veteran Affairs funded the study. The participants were recruited from the VA’s outpatient clinics and had a range of health problems typically associated with obesity, including type 2 diabetes, high blood pressure, high cholesterol and arthritis. We wanted to do a head-to-head comparison of two popular weight-loss methods: a low-carbohydrate diet and the drug orlistat.
Atkins: What was the low-carb protocol?
Yancy: We started people on 20 grams of carbohydrate per day. When they were halfway to their goal (or had severe cravings), we advised them to add 5 grams to their daily intake each week in a stepwise manner and depending on how close they were to their goal.
Atkins: How was this study different from earlier studies?
Yancy: Other studies had already indicated that a low-carbohydrate diet and prescription-strength orlistat combined with a low-fat diet are effective weight-loss therapies. But the two common strategies had not been compared to each other, an important omission now that orlistat, marketed as Alli, is available over-the-counter. In addition, few studies provide data on these treatments, particularly the low-carbohydrate diet, for overweight patients with chronic health issues. Most participants in other weight-loss studies are healthy and don’t have these problems. In fact, they are often excluded if they do.
Atkins: How would you describe the results?
Yancy: Both protocols proved equally effective at helping participants lose significant amounts of weight. The average weight loss for both groups was nearly 10 percent of their body weight, about 21 to 25 pounds over 48 weeks. Not many studies are able to achieve that significant a weight loss, which I attribute to the group counseling that was offered during the study. In fact, people tolerated orlistat better than I had expected. Orlistat use is often limited by gastrointestinal side effects, but these can be avoided, or at least lessened, by following a low-fat diet closely. We counseled participants in both groups fairly extensively about their respective diets. The two weight-loss methods also proved equally effective at improving cholesterol and glucose levels.
Atkins: But the difference in blood pressure reduction between the two protocols was the big surprise?
Yancy: Yes. I expected the weight loss to be considerable with both therapies but we were surprised to see blood pressure improve so much more with the low-carbohydrate diet than with orlistat. Systolic blood pressure dropped 5.9mm Hg in the low-carbohydrate group compared to 1.5mm Hg for the orlistat group, and diastolic dropped 4.5mm Hg compared to 0.4 mm Hg, respectively. At this point, the mechanism for the blood pressure improvement is unclear. While weight loss typically induces improvements in blood pressure, it may be that the low-carbohydrate diet has an additional effect, which might be the subject of future studies. There was another exciting benefit—nearly half of the patients in the low-carbohydrate group had their blood pressure medication decreased or discontinued while only 21 percent of those in the orlistat group experienced a reduction in medication use.
Atkins: What are the implications of the study?
Yancy: The findings send an important message to hypertensive people trying to lose weight. If they have high blood pressure and a weight problem, then a low-carbohydrate diet might be a better option than a weight-loss medication. It’s important to know you can try a diet instead of medication and get the same results with fewer costs and potentially fewer side effects. But it’s counseling patients on how to best follow the options that appears to be making the biggest impact. It is clear now that several diet options can work, so people can be given a choice of different ways to lose weight. But more importantly, we need to find new ways to help people maintain their new lifestyle.
For the abstract on the study please visit PubMed