Low-carb diet best for lowering blood pressure

Fresh vegetables are chopped in the kitchen of Revolution Foods in Los Angeles August 19, 2009.

NEW YORK (Reuters Health) - People with high blood pressure who want to drop some pounds may want to choose a low-carb diet, a new study shows.

In the study, overweight or obese individuals who went on a low-carb diet lost about the same amount of weight as those who cut down on their fat intake and took the weight-loss aid orlistat (sold as Xenical or Alli). However, the low-carb diet produced more favorable effects on blood pressure.

Most studies of weight loss methods have enrolled overweight or obese volunteers who were healthy, aside from weighing too much. The current study, in contrast, enrolled "real patients" with common conditions like diabetes and heart disease, William S. Yancy Jr. of the VA Medical Center in Durham, North Carolina, told Reuters Health. People with these health issues are often excluded from weight loss studies, Yancy said.

He and his colleagues assigned 146 patients to either receive instruction on eating a low-carbohydrate diet, and to start out by eating fewer than 20 grams of carbohydrate daily, or to take 120 mg of orlistat three times a day and receive instructions on eating a lower calorie, lower-fat diet. All of the study participants received diet instructions at group meetings, which were every two weeks for the first six months of the study, and monthly thereafter.

After 48 weeks, the low-carb group had lost about 9.5 percent of their body weight, compared to 8.5 percent for the orlistat group, which wasn't a significant difference. There also were similar improvements in cholesterol levels between the two groups. But the low carb diet did offer an advantage in terms of blood pressure reduction.

The low-carb group showed about a 6 percent drop in their systolic blood pressure (the top number in a blood pressure reading) and a 4.5 point drop in their diastolic pressure (the lower number). In contrast, the orlistat group did not see a drop in blood pressure; the corresponding changes for the orlistat group were 1.5 (systolic) and 0.4 (diastolic).

The two "fairly powerful weight loss treatments were equally effective, and one of them was more effective for lowering high blood pressure," Yancy said.

Orlistat works by blocking the body's absorption of fat from food so people who use the drug need to cut down on their fat intake or risk unpleasant side effects like gas and even incontinence.

Patients using orlistat in the current study were more likely to report gas, bowel incontinence, and diarrhea than those in the low-carb group. However, only one person stopped taking the drug due to these side effects. "Orlistat can work quite well if it's used correctly," Yancy said.

The group meetings for diet advice were a key element of success, Yancy added, with those who came to 80 percent or more of these visits losing an average of 14 percent to 15 percent of their body weight.

"I don't think that too many insurance (policies) would cover this," he said, "but I think it's something that needs to happen."

SOURCE: Archives of Internal Medicine, January 25, 2010.