Weight loss and reduction of blood pressure and hypertension.

The article in the current issue of Hypertension by Aucott et al1 raises some interesting questions. Does weight loss in the long term (ie, 3 years) result in a decrease in blood pressure (BP) levels? Is there difference in the effect of weight loss on decreased systolic BP (SBP) versus diastolic BP (DBP)? They combined 8 clinical trials and 8 cohort studies and tried to evaluate the linear relationship between change in BP and weight change. Overall, there was only a 2.8-kg weight loss, which resulted in a 1.9-mm decrease in DBP and 2.9 mm for SBP, neither of which were significant. Most important, the association between decrease in SBP with weight loss dissipated substantially over time (that is, 3 years from the onset of the study). The conclusion is that in long term, weight loss had little effect on change in BP levels. Weight loss has been a recommended nonpharmacological therapy for reducing BP levels for many years. Before the introduction of effective antihypertensive drug therapy, reduction of salt in the diet, weight loss, and mild sedation were recommended therapies for patients with nonmalignant hypertension.2 Previous meta-analyses of clinical trials on the effects of weight reduction on BP concluded that weight loss is important in both the prevention and treatment of hypertension.3 Most of the studies in the meta-analysis had relatively small sample sizes and short duration, usually 1 year. Is there really no health benefit of weight loss with decreased BP in the long term? To test such a hypothesis, participants would have to lose a substantial amount of weight (ie, 10 kg), have good BP measures before and after weight loss, a comparison group without substantial weight loss but having similar diet except for the differences in caloric intake or energy expenditure (ie, physical activity), and ideally not be on any antihypertensive drug therapy. Unfortunately, such a study does not exist. Long-term nonpharmacological intervention trials have been unsuccessful in maintaining weight loss (ie, 10 kg) for longer than 3 to 4 years after. Many of these trials have also included other dietary changes, especially sodium reduction, increases in fruits and vegetables (ie, potassium, etc), and exercise. Thus it is difficult to disentangle the effects of changes in the quality versus the quantity of the diet or amount of exercise and weight loss.4 The most puzzling study has been the 8-year follow-up of the Swedish Obese Subjects study. Three hundred forty-six obese participants had gastric surgery to reduce obesity and were matched with 346 obese controls that did not have surgery. Over 8 years, there was no weight loss in the controls and a substantial 20.1-kg weight loss for the surgical participants. There was a very substantial decrease in the risk of diabetes, as has been noted in other bariatric surgical studies. Surprisingly, however, there was no reduction in either the incidence of hypertension or BP levels over time between the 2 groups (ie, surgery and no surgery).5 The Diabetes Prevention Program, a nonpharmacological weight loss exercise trial among prediabetics with BMIs averaging 33 kg/m, reported that over an approximate 2.8-year follow-up that weight loss in the diet arm was about 5.6 kg, 2.1 kg in the metformin arm, and 0.1 in the placebo group. This resulted in a very substantial reduction in the risk of diabetes. There was a small 3.3 mm significant decrease in SBP and 3.1 mm of DBP in the diet arm, suggesting at least in the short term weight loss was associated with at least some decrease in BP.6 Longer term follow-up from this study will be reported shortly. However, maintenance of the weight loss has been difficult as in other studies. The PREMIER trial was a follow up of the successful Dietary Approaches to Stop Hypertension (DASH) diet feeding trial that demonstrated substantial reductions in BP in the short term. At 18 months in the PREMIER trial, there was only a 2.3-kg difference in weight between the advice only and the active intervention groups and only about a 2-mm difference in SBP. The investigators, however, reported a linear association between the change in SBP and the change in weight, even with the small amount of weight loss. They also documented that weight loss was the most important determinant of the decrease in SBP.7,8 The largest of the trials, the Trials of Hypertension Prevention (TOHPS) II trial, at 36 months demonstrated only a 0.2-kg weight loss in the diet–weight loss arm versus a 1.8-kg increase in usual care (ie, an overall 2-kg difference in weight), similar to the results in the PREMIER trial above. The SBP decreased 0.8 mm in the diet–weight loss arm and increased 0.6 mm in the usual care, a 1.4-mm difference.9 In the Women On the Move through Activity and Nutrition (WOMAN) Study, there was a 17-lb weight loss at 18 months in the lifestyle change (LC; intervention group) versus 3 lbs in the health education (HE) group.10 At 6 months there was a significant 5-mm decrease in SBP between the 2 groups, but by 18 months this had dissipated and the difference in SBP was no longer significant, 2.2 mm in the LC versus a decrease The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association. From the Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pa. Correspondence to Lewis H. Kuller, MD, DrPH, Distinguished University Professor of Public Health, University of Pittsburgh, Bellefield Professional Building, Room 550, 130 North Bellefield Avenue, Pittsburgh, PA 15213. E-mail [email protected] (Hypertension. 2009;54:00-00.) © 2009 American Heart Association, Inc.