A low-carbohydrate diet proved better at lowering blood pressure than orlistat and was as effective a method at helping patients lose weight, a head-to-head trial has reported in this week’s Archives of Internal Medicine.

Previous research had already separately shown that a low-carbohydrate diet, and a low-fat diet combined with orlistat, are both effective weight-loss therapies. It had also tended to exclude deliberately people with other chronic health issues – such as hypertension.

The authors of this paper, from Veterans Affairs Medical Center and Duke University Medical Center, North Carolina, US, have conducted the first direct comparison of the two weight-loss strategies. he researchers recruited 146 overweight people who had a range of health problems often seen in association with obesity – diabetes, hypertension and arthritis. Participants were assigned to a low-carbohydrate diet or to orlistat plus a low-fat diet; they were all also offered 48 weeks’ group counselling.

Orlistat was well tolerated. The authors say: “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 counselled people on orlistat in our study fairly extensively about the low-fat diet.”

On average, participants in both groups lost almost 10% of their body weight over the year’s follow-up. The authors attribute this unusual success to the counselling.

Both groups saw similar improvements in blood cholesterol and blood glucose levels.

However, there were significant differences between the groups in terms of blood pressure reduction: 47% of people in the low-carbohydrate diet group were able to reduce or stop their antihypertensive medication, against 21% of people in the orlistat plus low-fat diet group. Systolic blood pressure fell considerably more in the low-carbohydrate diet group than in the orlistat plus low-fat diet group.

The researchers say they are unsure why they saw the differences they did in blood pressure reduction: “[We] 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.


“While weight loss typically induces improvements in blood pressure, it may be that the low-carbohydrate diet has an additional effect.” That physiological effect may be the subject of future studies.

They conclude that many diet options are effective at weight loss, but including counselling seems to have 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.”