Weight reduction by dieting decreases blood pressure more than weight reduction with drugs

There have not yet been any trials which demonstrate that patients with essential hypertension who lose weight suffer more rarely from the secondary diseases typical of high blood pressure. However, weight reduction does reduce blood pressure. If weight is reduced by diet alone, the reduction in blood pressure is greater than if drugs are used to support the weight loss. Conclusions about the effectiveness of the diets are nevertheless uncertain, as in most trials there were deficiencies in the methods used. This was the conclusion reached by the final report of the Institute for Quality and Efficiency in Health Care (IQWiG), published by the researchers from Cologne on 6 November 2006.

This report is part of an extensive commission given by the Federal Joint Committee (G-BA) to the IQWiG on 22 February 2005. The Institute was commissioned to evaluate both drug and non-drug treatments for patients with long-term raised blood pressure without an organic cause (essential hypertension). In their new report, the Institute's researchers restricted their investigation to the influence of weight reduction on essential hypertension. The effects of diets and operations were studied, and also the activity of two drugs to support weight loss which had received regulatory approval in Germany at the start of the project. Drugs which specifically reduce blood pressure will be dealt with in a separate report.

17 trials included in the evaluation

The endpoints in the investigation were selected with the patient's point of view in mind. The IQWiG wanted to establish whether patients with high blood pressure could reduce their risk of suffering a stroke or heart attack (for example) by losing weight and whether their disease-related quality of life improves. A reduction in blood pressure is admittedly an indication that the risks have been reduced. However, not all methods to reduce blood pressure decrease the risk of (for example) heart damage in the same manner. The duration and degree of the reduction in blood pressure and other parameters of blood pressure control were therefore considered as surrogate parameters.

The IQWiG researchers only included the trials in the evaluation in which the intervention was intended to lead to weight reduction. The duration of the trials had to be at least 24 weeks.

The authors identified 17 trials related to the questions in the commission. These included seven trials using drugs to reduce weight. The other trials dealt with various non-drug approaches, such as diets. There were no relevant trials on operations to reduce the size of the stomach, such as the "gastric band" or "gastric balloon". Many of the identified trials had methodological defects, which greatly restricted the reliability of their conclusions. This applied particularly to the trials on diets.

Sibutramine not shown to reduce blood pressure

The IQWiG evaluation concluded that none of the trials considered in the report enabled any conclusion about patient-relevant endpoints. Therefore nothing could be said about the long-term benefit of weight reduction in essential hypertension. For example, there was no information about reduction in the risk of secondary diseases.

With a treatment period of up to one year, diets were capable of reducing both weight and blood pressure (systolic by ca. 3 to 10 mm Hg, diastolic by ca. 1 to 6 mm Hg).

The active substances orlistat (trade name: Xenical) and sibutramine (trade name: Reductil) could reduce hypertensive patients' weight. In all trials, the reduction in weight was statistically significant in comparison to placebo. However, a reduction in blood pressure was only demonstrated for orlistat (systolic ca. 0 to 4 mm Hg, diastolic ca. 1 to 3 mm Hg). This was not demonstrated for sibutramine. Sibutramine can increase blood pressure at higher doses. Higher doses do not have regulatory approval in Germany. Adverse side effects occurred with both orlistat and sibutramine.

The active substance rimonobant (trade name: Accomplia) was not evaluated by IQWiG, as it had not yet been approved in Germany when the commission was assigned.

The report makes no statements of any sort about the possible consequences of losing weight, for example, on the prevention of metabolic diseases or in other patient groups. There is also the question of the efficacy of losing weight in combination with other measures. This was not investigated in the report and is the object of an independent project.

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