BACKGROUND: All major guidelines for antihypertensive therapy recommend weight loss. Dietary interventions that aim to reduce body weight might therefore be a useful intervention to reduce blood pressure and adverse cardiovascular events associated with hypertension.
OBJECTIVES: Primary objectives To assess the long-term effects of weight-reducing diets in people with hypertension on all-cause mortality, cardiovascular morbidity, and adverse events (including total serious adverse events, withdrawal due to adverse events, and total non-serious adverse events). Secondary objectives To assess the long-term effects of weight-reducing diets in people with hypertension on change from baseline in systolic blood pressure, change from baseline in diastolic blood pressure, and body weight reduction.
SEARCH METHODS: For this updated review, the Cochrane Hypertension Information Specialist searched the following databases for randomised controlled trials up to April 2020: the Cochrane Hypertension Specialised Register, CENTRAL (2020, Issue 3), Ovid MEDLINE, Ovid Embase, and ClinicalTrials.gov. We also contacted authors of relevant papers about further published and unpublished work. The searches had no language restrictions.
SELECTION CRITERIA: We included randomised controlled trials (RCTs) of at least 24 weeks' duration that compared weight-reducing dietary interventions to no dietary intervention in adults with primary hypertension.
DATA COLLECTION AND ANALYSIS: Two review authors independently assessed risks of bias and extracted data. Where appropriate and in the absence of significant heterogeneity between studies (P > 0.1), we pooled studies using a fixed-effect meta-analysis. In case of moderate or larger heterogeneity as measured by Higgins I2, we used a random-effects model.
MAIN RESULTS: This second review update did not reveal any new trials, so the number of included trials remains the same: eight RCTs involving a total of 2100 participants with high blood pressure and a mean age of 45 to 66 years. Mean treatment duration was 6 to 36 months. We judged the risks of bias as unclear or high for all but two trials. No study included mortality as a predefined outcome. One RCT evaluated the effects of dietary weight loss on a combined endpoint consisting of the necessity of reinstating antihypertensive therapy and severe cardiovascular complications. In this RCT, weight-reducing diet lowered the endpoint compared to no diet: hazard ratio 0.70 (95% confidence interval (CI) 0.57 to 0.87). None of the trials evaluated adverse events as designated in our protocol. The certainty of the evidence was low for a blood pressure reduction in participants assigned to weight-loss diets as compared to controls: systolic blood pressure: mean difference (MD) -4.5 mm Hg (95% CI -7.2 to -1.8 mm Hg) (3 studies, 731 participants), and diastolic blood pressure: MD -3.2 mm Hg (95% CI -4.8 to -1.5 mm Hg) (3 studies, 731 participants). We judged the certainty of the evidence to be high for weight reduction in dietary weight loss groups as compared to controls: MD -4.0 kg (95% CI -4.8 to -3.2) (5 trials, 880 participants). Two trials used withdrawal of antihypertensive medication as their primary outcome. Even though we did not consider this a relevant outcome for our review, the results of these RCTs strengthen the finding of a reduction of blood pressure by dietary weight-loss interventions.
AUTHORS' CONCLUSIONS: In this second update, the conclusions remain unchanged, as we found no new trials. In people with primary hypertension, weight-loss diets reduced body weight and blood pressure, but the magnitude of the effects are uncertain due to the small number of participants and studies included in the analyses. Whether weight loss reduces mortality and morbidity is unknown. No useful information on adverse effects was reported in the relevant trials.
OBJECTIVE: We conducted this systematic review to support the U.S. Preventive Services Task Force (USPSTF) in updating its 2012 recommendation on screening for and treatment of adult obesity. Our review addressed three key questions: 1) Do primary care–relevant behavioral and/or pharmacotherapy weight loss and weight loss maintenance interventions lead to improved health outcomes among adults who are overweight or have obesity and are a candidate for weight loss interventions? 2) Do primary care–relevant behavioral and/or pharmacotherapy weight loss and weight loss maintenance interventions lead to weight loss, weight loss maintenance, or a reduction in the incidence or prevalence of obesity-related conditions among adults who are overweight or have obesity and are a candidate for weight loss interventions? 3) What are the adverse effects of primary care–relevant behavioral and/or pharmacotherapy weight loss and weight loss maintenance interventions in adults who are overweight or have obesity and are a candidate for weight loss interventions?
DATA SOURCES: We performed a search of MEDLINE, PubMed Publisher-Supplied, PsycINFO, and the Cochrane Central Registry of Controlled Trials for studies published through June 6, 2017. Studies included in the 2011 USPSTF review were re-evaluated for potential inclusion. We supplemented searches by examining reference lists from related articles and expert recommendations and searched federal and international trial registries for ongoing trials. We conducted ongoing surveillance through March 23, 2018 to identify any major studies published in the interim.
STUDY SELECTION: Two researchers reviewed 15,483 titles and abstracts and 572 full-text articles against prespecified inclusion criteria. Eligible studies were those that focused on weight loss in adults who are overweight or have obesity, or maintenance of previous weight loss. Trials among populations selected based on the presence of a chronic disease in which weight loss or maintenance is part of disease management (e.g., known cardiovascular disease, type 2 diabetes) were excluded. Studies included for health and intermediate outcomes (including weight loss) were randomized or clinically controlled trials that report data at least 12 months following the start of the intervention. In addition, for studies of potential harms of interventions we included large cohort, case-control, or event monitoring studies in addition to trials with fewer than 12 months of followup. Included interventions were those conducted in or recruited from primary care or a health care system or were judged to be feasible for implementation or referral from primary care and included behavior-based interventions as well as five U.S. Food and Drug Administration–approved medications for long-term chronic weight management (liraglutide, lorcaserin, naltrexone and bupropion, orlistat, and phentermine-topiramate). Studies of surgical and nonsurgical weight loss devices and procedures were excluded. We conducted dual, independent critical appraisal of all provisionally included studies and abstracted all important study details and results from all studies rated fair or good quality. Data were abstracted by one reviewer and confirmed by another.
DATA ANALYSIS: We synthesized data for behavior- and medication-based weight loss and weight loss maintenance interventions separately. Health outcomes and harms were sparsely reported and the specific outcomes measured differed across trials, precluding meta-analysis, so we summarized those data in tables and narratively. For weight loss outcomes related to behavior-based weight loss interventions, we ran random-effects meta-analyses using the DerSimonian and Laird method to calculate the pooled differences in mean changes (for continuous data) and pooled risk ratio (for binary data). We examined statistical heterogeneity among the pooled studies using standard χ2 tests and estimated the proportion of total variability in point estimates using the I2 statistic. Meta-regression was used to explore potential effect modification by various study, population, and intervention characteristics. We generated funnel plots and conducted tests for small-study effects for all pooled analyses. Meta-analysis of the medication trials was not performed due to the small number of included trials and inconsistency in outcome reporting; therefore, results from these trials were summarized narratively and in illustrative forest plots. Using established methods, we assessed the strength of evidence for each question.
RESULTS: We included 124 studies that were reported in 238 publications. We carried forward 41 studies from our previous review and 83 new studies were added. Of the 124 included studies, 89 trials focused on behavior-based weight loss (80 trials) or weight loss maintenance (nine trials) interventions. Thirty-five studies addressed medications for weight loss (32 studies) or weight loss maintenance (three trials). The majority of trials took place in the United States. Over half (73 trials) represented a general, unselected population of adults who were eligible for participation based on being overweight or having obesity; the remaining trials specifically enrolled participants who were also at elevated clinical or subclinical risk of cardiovascular disease or cancer. The mean baseline body mass index ranged from 25 to 42 kg/m2 and mean age ranged from 22 to 66 years. Eleven trials focused on specific racial/ethnic groups (African American, Asians and South Asians, American Indian, or those of Hispanic ethnicity). In the remaining trials, race/ethnicity and socioeconomic status were not well reported and when described, the majority of participants were white, with medium to high socioeconomic status. The behavior-based interventions were highly variable across the included trials in terms of the modes of delivery, number of sessions and contacts, and interventionists. Across the 120 intervention arms, the primary mode of intervention delivery was: group based (41 arms), individual-based (37 arms), technology-based (22 arms), “mixed” (18 arms), or print only (two arms). Twenty-three interventions included interaction with a primary care provider. The 41 medication-based studies addressed: liraglutide (four trials), lorcaserin (four trials), naltrexone and bupropion (three trials), orlistat (19 trials, two observational studies), and phentermine-topiramate (three trials).HEALTH OUTCOMES: Health outcomes were minimally reported in the behavior-based weight loss and maintenance trials (k=20; n=9910). In four weight loss trials (n=4442) reporting mortality, there were no significant differences between groups over 2 to 16 years. Two weight loss trials (n=2666) reported on cardiovascular events, with neither finding differences between groups over 3 and 10 years, respectively. Health-related quality of life (QOL) was evaluated in 17 weight loss and maintenance trials (n=7120), with almost all showing no differences between groups. Trials of medication-based weight loss interventions examined few health outcomes beyond QOL (k=10; n=13,145). Although most studies showed evidence of a greater improvement in obesity-specific QOL among those on medication compared with placebo, the differences were small and of unclear clinical significance. In addition, interpretation of these finding was limited given high study dropout rates (≥35% in half the included trials). Two medication-based trials (n=6210) examined cardiovascular events, finding few events in any group. None of the medication-based maintenance trials reported the effects of the interventions on health outcomes. WEIGHT OUTCOMES: Pooled results of 67 behavior-based weight loss trials indicated greater weight loss from interventions compared to control conditions at 12 to 18 months (mean difference in weight change [MD], −2.39 kg [−5.3 lb] [95% CI, −2.86 to −1.93]; k=67; n=22,065; I2=90.0%). Mean absolute changes in weight ranged from −0.5 kg (−1.1 lb) to −9.3 kg (−20.5 lb) among intervention participants and from 1.4 kg (3.0 lb) to −5.6 (−12.3 lb) among control participants. Weight change at followup beyond 12 to 18 months was not as well reported but effects were consistent with short-term weight loss, although generally attenuated, over time. A meta-analysis of 38 trials found that intervention participants had a 1.94 times greater probability of losing 5 percent of their initial weight compared with control groups over 12 to 18 months (risk ratio [RR], 1.94 [95% CI, 1.70 to 2.22]; k=38; n=12,231; I2=67.2%), which translated into a number needed to treat of 8. Among the majority of trials of behavior-based weight loss maintenance interventions, both intervention and control participants regained weight over 12 to 18 months of maintenance; however, the intervention participants experienced less weight regain (pooled MD, −1.59 kg [−3.5 lb] [95% CI, −2.38 to −0.79]; k=8; n=1408; I2=26.8%). Among 32 medication-based weight loss trials, those randomized to medications experienced greater weight loss compared to those on placebo at 12 to 18 months (mean/least squares mean [LSM] MD ranged from −1.0 kg [−2.2 lb] to −5.8 kg [−12.8 lb]; no meta-analysis conducted). Absolute changes in weight ranged from mean/LSM of −3.3 kg (−7.3 lb) to −10.5 kg (−23.4 lb) among medication participants compared to −0.9 kg (−2.0 lb) to −7.6 kg (−16.8 lb) among placebo participants over 12 to 18 months. Medication participants had a 1.2 to 3.9 times greater probability of losing 5 percent of their initial weight compared with placebo participants over 12 to 18 months. Three medication-based trials indicate greater weight maintenance in medication than placebo participants over 12 to 36 months (MD ranged from −0.6 to −3.5; no meta-analysis conducted). INTERMEDIATE OUTCOMES: Thirteen trials (n=4095) examined incident diabetes among those in behavior-based interventions compared to control conditions. Absolute cumulative incidence of diabetes at up to 3 years of followup ranged from 0 to 15 percent in the intervention group and 0 to 29 percent in controls. The DPP and Finnish DPS trials found statistically significant lower incidences of developing diabetes at 3 to 9 years; no other trial found differences between groups. However, these trials generally had smaller sample sizes and shorter followup. The pooled relative risk of developing incident diabetes was 0.67 (95% CI, 0.51 to 0.89; k=9; n=3140; I2=49.2%). Four trials of weight loss medications (three weight loss and one maintenance trial) examined incident diabetes. Absolute cumulative incidence of diabetes at up to 4 years of followup ranged from 0 to 6 percent in medication arms and 1 to 11 percent in placebo arms; between-group differences were statistically different in most medication trials. Prevalence of hypertension, metabolic syndrome, use of CVD medications, and estimated 10-year risk of CVD were sparsely reported. There was limited evidence from larger trials that those in behavior-based weight loss arms had reduced prevalence of hypertension and use of CVD medications compared to control conditions; data were limited and mixed for metabolic syndrome and 10-year CVD risk. Four medication trials reported on use of lipid-lowering and antihypertensive medications, prevalence of metabolic syndrome, and 10-year CVD risk score with mixed results. ADVERSE EVENTS: There were no serious harms related to the behavior-based interventions and most trials noted no differences between groups in the rates of adverse events, including cardiovascular events. In the three behavior-based trials large enough to examine musculoskeletal issues between groups, results were mixed. Although serious adverse events were relatively uncommon in medication trials and generally similar between groups, adverse event rates were high in both groups by 12 months, with 80 to 96 percent experiencing an adverse event in the medication arms compared with 63 to 94 percent in the placebo arms. The higher rates of adverse events in the medication arms resulted in higher dropout rates than in the placebo arms.
CONCLUSION: We found that behavior-based weight-loss interventions with or without weight loss medications resulted in more weight loss than usual care conditions. The degree of weight loss we observed with the behavior-based weight loss interventions in the current review is slightly smaller but consistent in magnitude with our 2011 review on this topic. As in the previous review, we noted that weight loss interventions resulted in a decreased risk of developing diabetes, particularly among those with prediabetes, although the prevalence of other intermediate health outcomes was less well reported. Limited evidence exists regarding health outcomes associated with weight loss interventions. Weight loss medications, but not behavior-based interventions, were associated with higher rates of harms compared with control arms. Heterogeneity within each individual intervention arm confounded with differences in the populations, settings, and trial quality, making it difficult to disentangle which variables may be driving larger effects. Long-term weight and health outcomes data, as well as data on important subgroups (e.g. those who are older, nonwhite, or overweight) were lacking and should be a high priority for future study.
BACKGROUND: The prevalence of overweight and obesity is increasing globally, an increase which has major implications for both population health and costs to health services. This is an update of a Cochrane Review.
OBJECTIVES: To assess the effects of strategies to change the behaviour of health professionals or the organisation of care compared to standard care, to promote weight reduction in children and adults with overweight or obesity.
SEARCH METHODS: We searched the following databases for primary studies up to September 2016: CENTRAL, MEDLINE, Embase, CINAHL, DARE and PsycINFO. We searched the reference lists of included studies and two trial registries.
SELECTION CRITERIA: We considered randomised trials that compared routine provision of care with interventions aimed either at changing the behaviour of healthcare professionals or the organisation of care to promote weight reduction in children and adults with overweight or obesity.
DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane when conducting this review. We report the results for the professional interventions and the organisational interventions in seven 'Summary of findings' tables.
MAIN RESULTS: We identified 12 studies for inclusion in this review, seven of which evaluated interventions targeting healthcare professional and five targeting the organisation of care. Eight studies recruited adults with overweight or obesity and four recruited children with obesity. Eight studies had an overall high risk of bias, and four had a low risk of bias. In total, 139 practices provided care to 89,754 people, with a median follow-up of 12 months. Professional interventions Educational interventions aimed at general practitioners (GPs), may slightly reduce the weight of participants (mean difference (MD) -1.24 kg, 95% confidence interval (CI) -2.84 to 0.37; 3 studies, N = 1017 adults; low-certainty evidence).Tailoring interventions to improve GPs' compliance with obesity guidelines probably leads to little or no difference in weight loss (MD 0.05 (kg), 95% CI -0.32 to 0.41; 1 study, N = 49,807 adults; moderate-certainty evidence).It is uncertain if providing doctors with reminders results in a greater weight reduction than standard care (men: MD -11.20 kg, 95% CI -20.66 kg to -1.74 kg, and women: MD -1.30 kg, 95% CI [-7.34, 4.74] kg; 1 study, N = 90 adults; very low-certainty evidence).Providing clinicians with a clinical decision support (CDS) tool to assist with obesity management at the point of care leads to little or no difference in the body mass index (BMI) z-score of children (MD -0.08, 95% CI -0.15 to -0.01 in 378 children; moderate-certainty evidence), CDS tools may lead to little or no difference in weight loss in adults: MD -0.095 kg (-0.21 lbs), P = 0.47; 1 study, N = 35,665; low-certainty evidence. Organisational interventions Adults with overweight or obesity may lose more weight if the care was provided by a dietitian (by -5.60 kg, 95% CI -4.83 kg to -6.37 kg) or by a doctor-dietitian team (by -6.70 kg, 95% CI -7.52 kg to -5.88 kg; 1 study, N = 270 adults; low-certainty evidence). Shared care leads to little or no difference in the BMI z-score of children with obesity (adjusted MD -0.05, 95% CI -0.14 to 0.03; 1 study, N = 105 children; low-certainty evidence).Organisational restructuring of the delivery of primary care (i.e. introducing the chronic care model) may result in a slightly lower increase in the BMI of children who received care at intervention clinics (BMI change: adjusted MD -0.21, 95% CI -0.50 to 0.07; 1 study, unadjusted MD -0.18, 95% CI -0.20 to -0.16; N=473 participants; moderate-certainty evidence).Mail and phone interventions probably lead to little or no difference in weight loss in adults (mean weight change (kg) using mail: -0.36, 95% CI -1.18 to 0.46; phone: -0.44, 95% CI -1.26 to 0.38; 1 study, N = 1801 adults; moderate-certainty evidence). Care delivered by a nurse at a primary care clinic may lead to little or no difference in the BMI z-score in children (MD -0.02, 95% CI -0.16 to 0.12; 1 study, N = 52 children; very low-certainty evidence).Two studies reported data on cost effectiveness: one study favoured mail and standard care over telephone consultations, and the other study achieved weight loss at a modest cost in both intervention groups (doctor and doctor-dietitian). One study of shared care reported similar adverse effects in both groups.
AUTHORS' CONCLUSIONS: We found little convincing evidence for a clinically-important effect on participants' weight or BMI of any of the evaluated interventions. While pooled results from three studies indicate that educational interventions targeting healthcare professionals may lead to a slight weight reduction in adults, the certainty of these results is low. Two trials evaluating CDS tools (unpooled results) for improved weight management suggest little or no effect on weight or BMI change in adults or children with overweight or obesity. Evidence for all the other interventions evaluated came mostly from single studies. The certainty of the included evidence varied from moderate to very low for the main outcomes (weight and BMI). All of the evaluated interventions would need further investigation to ascertain their strengths and limitations as effective strategies to change the behaviour of healthcare professionals or the organisation of care. As only two studies reported on cost, we know little about cost effectiveness across the evaluated interventions.
BACKGROUND: Overweight and obesity have negative health effects. Primary care clinicians are best placed to intervene in weight management. Previous reviews of weight loss interventions have included studies from specialist settings. The aim of this review was to estimate the effect of behavioural interventions delivered in primary care on body weight in overweight and obese adults.
METHODS: The review included randomized controlled trials (RCTs) of behavioural interventions in obese or overweight adult participants in a primary care setting, with weight loss as the primary outcome, and a minimum of 12 months of follow-up. A systematic search strategy was implemented in Medline, Embase, Web of Science and the Cochrane Central Registry of Controlled Trials. Risk of bias was assessed using the Cochrane Risk of Bias tool and behavioural science components of interventions were evaluated. Data relating to weight loss in kilograms were extracted, and the results combined using meta-analysis.
RESULTS: Fifteen RCTs, with 4539 participants randomized, were selected for inclusion. The studies were heterogeneous with respect to inclusion criteria and type of intervention. Few studies reported interventions informed by behavioural science theory. Pooled results from meta-analysis indicated a mean weight loss of -1.36 kg (-2.10 to -0.63, P < 0.0001) at 12 months, and -1.23 kg (-2.28 to -0.18, P = 0.002) at 24 months.
CONCLUSION: Behavioural weight loss interventions in primary care yield very small reductions in body weight, which are unlikely to be clinically significant. More effective management strategies are needed for the treatment of overweight and obesity.
BACKGROUND: Obesity is a major public health issue. This review updates the evidence on the effectiveness of behavioural and pharmacologic treatments for overweight and obesity in adults.
METHODS: We updated the search conducted in a previous review. Randomized trials of primary-care-relevant behavioural (diet, exercise and lifestyle) and pharmacologic (orlistat and metformin) with or without behavioural treatments in overweight and obese adults were included if 12-month, postbaseline data were provided for weight outcomes. Studies reporting harms were included regardless of design. Data were extracted and pooled wherever possible for 5 weight outcomes, 6 secondary health outcomes and 4 adverse events categories.
RESULTS: We identified 68 studies, most consisted of short-term (≤ 12 mo) treatments using diet (n = 8), exercise (n = 4), diet and exercise (n = 10), lifestyle (n = 19), orlistat (n = 25) or metformin (n = 4). Compared with the control groups, intervention participants had a greater weight loss of -3.02 kg (95% confidence interval [CI] -3.52 to -2.52), a greater reduction in waist circumference of -2.78 cm (95% CI -3.34 to -2.22) and a greater reduction in body mass index of -1.11 kg/m(2) (95% CI -1.39 to -0.84). The relative risk for loss of ≥ 5% body weight was 1.77 (95% CI 1.58-1.99, [number needed to treat 5, 95% CI 4-7]), and the relative risk for loss of ≥ 10% body weight was 1.91 (95% CI 1.69-2.16, [number needed to treat 9, 95% CI 7-12]). Incidence of type 2 diabetes was lower among pre-diabetic intervention participants (relative risk 0.62 [95% CI 0.50-0.77], number needed to treat 17 [95% CI 13-29]). With prevalence rates for type 2 diabetes on the rise, weight loss coupled with a reduction in the incidence of type 2 diabetes could potentially have a significant benefit on population health and a possible reduction in need for drug treatments for glycemic control.
INTERPRETATION: There is moderate quality evidence that behavioural and pharmacologic plus behvioural, treatments for overweight and obesity in adults lead to clinically important reductions in weight and incidence of type 2 diabetes in pre-diabetic populations.
REGISTRATION: PROSPERO no. CRD42012002753.
The objective of this article was twofold (1) to determine the existence and effectiveness of interventions to improve health professionals' management of obesity or the organization of care for overweight and obese people; and (2) to update a previous systematic review on this topic with new or additional studies. The study design was a systematic review of intervention studies, undertaken according to standard methods developed by the Cochrane Effective Practice and Organization of Care (EPOC) Group. Participants were trained health care professionals and overweight and obese patients. The measurements were objective measures of health professionals' practice and behaviours, and patient outcomes including satisfaction, behaviour, psychological factors, disease status, risk factors and measures of body weight, fat, or body mass index (BMI). Twelve studies were included in the original review. A further six were included in this update. Six of the 18 studies were randomized controlled trials of health professional-oriented interventions (such as the use of reminders and training) and one was a controlled before-and-after study to improve collaboration between a hospital clinic and general practitioners (GPs). Ten randomized controlled trials and two controlled clinical trials of interventions comparing either the deliverer of weight-loss interventions or the setting of the delivery of the intervention, were identified. The heterogeneity and generally limited quality of identified studies make it difficult to provide recommendations for improving health professionals' obesity management. To conclude, at present, there are few solid leads about improving obesity management, although reminder systems, brief training interventions, shared care, inpatient care and dietitian-led treatments may all be worth further investigation. Therefore, decisions for the improvement of provision of services must be based on the existing evidence on interventions with patients and good clinical judgement. Further research is needed to identify cost-effective strategies for improving the management of obesity. A full version of this review (including detailed descriptions of the included studies and their methodological quality, and results and excluded studies tables) is available in the Cochrane Library. The Cochrane Library is a database of systematic review and other evidence on the effects of health care, continuously updated as new information emerges. It is available on CD ROM from Update Software. For further information see: http://www.update-software.com/cochrane.
All major guidelines for antihypertensive therapy recommend weight loss. Dietary interventions that aim to reduce body weight might therefore be a useful intervention to reduce blood pressure and adverse cardiovascular events associated with hypertension.
OBJECTIVES:
Primary objectives To assess the long-term effects of weight-reducing diets in people with hypertension on all-cause mortality, cardiovascular morbidity, and adverse events (including total serious adverse events, withdrawal due to adverse events, and total non-serious adverse events). Secondary objectives To assess the long-term effects of weight-reducing diets in people with hypertension on change from baseline in systolic blood pressure, change from baseline in diastolic blood pressure, and body weight reduction.
SEARCH METHODS:
For this updated review, the Cochrane Hypertension Information Specialist searched the following databases for randomised controlled trials up to April 2020: the Cochrane Hypertension Specialised Register, CENTRAL (2020, Issue 3), Ovid MEDLINE, Ovid Embase, and ClinicalTrials.gov. We also contacted authors of relevant papers about further published and unpublished work. The searches had no language restrictions.
SELECTION CRITERIA:
We included randomised controlled trials (RCTs) of at least 24 weeks' duration that compared weight-reducing dietary interventions to no dietary intervention in adults with primary hypertension.
DATA COLLECTION AND ANALYSIS:
Two review authors independently assessed risks of bias and extracted data. Where appropriate and in the absence of significant heterogeneity between studies (P > 0.1), we pooled studies using a fixed-effect meta-analysis. In case of moderate or larger heterogeneity as measured by Higgins I2, we used a random-effects model.
MAIN RESULTS:
This second review update did not reveal any new trials, so the number of included trials remains the same: eight RCTs involving a total of 2100 participants with high blood pressure and a mean age of 45 to 66 years. Mean treatment duration was 6 to 36 months. We judged the risks of bias as unclear or high for all but two trials. No study included mortality as a predefined outcome. One RCT evaluated the effects of dietary weight loss on a combined endpoint consisting of the necessity of reinstating antihypertensive therapy and severe cardiovascular complications. In this RCT, weight-reducing diet lowered the endpoint compared to no diet: hazard ratio 0.70 (95% confidence interval (CI) 0.57 to 0.87). None of the trials evaluated adverse events as designated in our protocol. The certainty of the evidence was low for a blood pressure reduction in participants assigned to weight-loss diets as compared to controls: systolic blood pressure: mean difference (MD) -4.5 mm Hg (95% CI -7.2 to -1.8 mm Hg) (3 studies, 731 participants), and diastolic blood pressure: MD -3.2 mm Hg (95% CI -4.8 to -1.5 mm Hg) (3 studies, 731 participants). We judged the certainty of the evidence to be high for weight reduction in dietary weight loss groups as compared to controls: MD -4.0 kg (95% CI -4.8 to -3.2) (5 trials, 880 participants). Two trials used withdrawal of antihypertensive medication as their primary outcome. Even though we did not consider this a relevant outcome for our review, the results of these RCTs strengthen the finding of a reduction of blood pressure by dietary weight-loss interventions.
AUTHORS' CONCLUSIONS:
In this second update, the conclusions remain unchanged, as we found no new trials. In people with primary hypertension, weight-loss diets reduced body weight and blood pressure, but the magnitude of the effects are uncertain due to the small number of participants and studies included in the analyses. Whether weight loss reduces mortality and morbidity is unknown. No useful information on adverse effects was reported in the relevant trials.
