Can we rely on the best trial? A comparison of individual trials and systematic reviews Determinants of weight loss maintenance: a systematic review. Mixed treatment comparison analysis provides internally coherent treatment effect estimates based on overviews of reviews and can reveal inconsistency. How to write an evidence-based clinical review article. Green tea (Camellia sinensis) and cancer prevention: a systematic review of randomized trials and epidemiological studies Methods for evidence synthesis in the case of very few studies Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach Symposium integrating evidence-based medicine into clinical practice. Does the use of an electronic reminder device with or without counseling improve adherence to lipid-lowering treatment? The results of a randomized controlled trial Risk Factors for Erosive Esophagitis: A Multivariate Analysis Based on the ProGERD Study Initiative Sources of evidence for systematic reviews of interventions in diabetes. Effects of workplace-based dietary and/or physical activity interventions for weight management targeting healthcare professionals: a systematic review of randomised controlled trials A systematic review protocol examining the effect of vitamin D supplementation on endothelial function INVITED COMMENTARY: Rating the Quality of Trials in Systematic Reviews of Physical Therapy Interventions Treatment of surgical patients is evidence-based. The Effectiveness of Psychosocial Interventions as Adjuncts to Orthopaedic Surgery: A Systematic Review Protocol Key Steps in Conducting Systematic Reviews for Underpinning Clinical Practice Guidelines: Methodology of the European Association of Urology. Identifying, documenting, and examining heterogeneity in systematic reviews of complex interventions.
Background The ideal evidence to answer a question about the effectiveness of treatment is a systematic review . However , for many clinical questions a systematic review will not be available , or may not be up to date . One option could be to use the evidence from an individual trial to answer the question ? Methods We assessed how often ( a ) the estimated effect and ( b ) the p-value in the most precise single trial in a meta- analysis agreed with the whole meta- analysis . For a r and om sample of 200 completed Cochrane Review s ( January , 2005 ) we identified a primary outcome and extracted : the number of trials , the statistical weight of the most precise trial , the estimate and confidence interval for both the highest weighted trial and the meta- analysis overall . We calculated the p-value for the most precise trial and meta- analysis . Results Of 200 review s , only 132 provided a meta- analysis of 2 or more trials , with a further 35 effect estimates based on single trials . The average number of trials was 7.3 , with the most precise trial contributing , on average , 51 % of the statistical weight to the summary estimate from the whole meta- analysis . The estimates of effect from the most precise trial and the overall meta-analyses were highly correlated ( rank correlation of 0.90).There was an 81 % agreement in statistical conclusions . Results from the most precise trial were statistically significant in 60 of the 167 evaluable review s , with 55 of the corresponding systematic review s also being statistically significant . The five discrepant results were not strikingly different with respect to their estimates of effect , but showed considerable statistical heterogeneity between trials in these meta-analyses . However , among the 101 cases in which the most precise trial was not statistically significant , the corresponding meta-analyses yielded 31 statistically significant results . Conclusions Single most precise trials provided similar estimates of effects to those of the meta-analyses to which they contributed , and statistically significant results are generally in agreement . However , " negative " results were less reliable , as may be expected from single underpowered trials . For systematic review ers we suggest that : ( 1 ) key trial(s ) in a review deserve greater attention ( 2 ) systematic review ers should check agreement of the most precise trial and the meta analysis . For clinicians using trials we suggest that when a meta- analysis is not available , a focus on the most precise trial is reasonable provided it is adequately powered BACKGROUND Discerning the determinants of weight loss maintenance is important in the planning of future interventions and policies regarding overweight and obesity . We have therefore systematic ally synthesized recent literature on determinants of weight loss maintenance for individuals with overweight and obesity . METHODS With the use of the Preferred Reporting Items for Systematic Review s and Meta-Analyses statement , prospect i ve studies were identified from search es in PubMed and PsycINFO from 2006 to 2016 . We included articles investigating adults with overweight and obesity undergoing weight loss without surgery or medication .  Included articles were scored on their method ological quality , and a best- evidence synthesis was applied to summarize the results . RESULTS Our search result ed in 8,222 articles of which 67 articles were selected . In total , 124 determinants were identified of which 5 were demographic , 59 were behavioural , 51 were psychological/cognitive and 9 were social and physical environmental determinants . We found consistent evidence that demographic determinants were not predictive of weight loss maintenance . Behavioural and cognitive determinants that promote a reduction in energy intake , an increase in energy expenditure and monitoring of this balance are predictive determinants . CONCLUSION This review identifies key determinants in weight loss maintenance . However , more research regarding cognitive and environmental determinants of weight loss maintenance is needed to advance our knowledge on determinants of weight loss maintenance OBJECTIVES To propose methods for mixed treatment comparisons ( MTC ) based on pooled summaries of the type produced in overviews of review s. STUDY DESIGN AND SETTING Overviews of review s ( umbrella review s ) summarize the results of multiple systematic review s into a single document . They report the summary estimates from the original pairwise meta-analyses and discuss them in narrative form , with the intention of identifying the most effective treatment . We present methods for MTC synthesis , tailored for use with overviews of review s. These generate a single internally consistent summary of all the relative treatment effects and assessment s of whether the summary is consistent with the data . These methods are applied to a published overview of treatments for childhood nocturnal enuresis . We apply the methods to both fixed-effect ( FE ) and r and om-effects ( RE ) meta-analyses of the original trials . RESULTS The summary relative risks based on FE meta-analyses , as originally published , were highly inconsistent . Those based on RE meta-analyses were consistent and could , given st and ard assumptions on comparability of treatment effects in meta- analysis , form a basis for coherent decision making . CONCLUSION Along with the summaries from systematic review s , MTC methods should be used in overviews to provide a single coherent analysis of all treatment comparisons and to check for evidence consistency Traditional clinical review articles , also known as up date s , differ from systematic review s and meta-analyses . Up date s selectively review the medical literature while discussing a topic broadly . Non-quantitative systematic review s comprehensively examine the medical literature , seeking to identify and synthesize all relevant information to formulate the best approach to diagnosis or treatment . Meta-analyses ( quantitative systematic review s ) seek to answer a focused clinical question , using rigorous statistical analysis of pooled research studies . This article presents guidelines for writing an evidence -based clinical review article for American Family Physician . First , the topic should be of common interest and relevance to family practice . Include a table of the continuing medical education objectives of the review . State how the literature search was done and include several sources of evidence -based review s , such as the Cochrane Collaboration , BMJ 's Clinical Evidence , or the InfoRetriever Web site . Where possible , use evidence based on clinical outcomes relating to morbidity , mortality , or quality of life , and studies of primary care population s. In articles su bmi tted to American Family Physician , rate the level of evidence for key recommendations according to the following scale : level A ( r and omized controlled trial [ RCT ] , meta- analysis ) ; level B ( other evidence ) ; level C ( consensus/expert opinion ) . Finally , provide a table of key summary points Background Green tea is one of the most popular beverages worldwide . This review summarizes the beneficial effects of green tea on cancer prevention . Methods Electronic data bases , including PubMed ( 1966–2008 ) , the Cochrane Library ( Issue 1 , 2008 ) and Chinese Biomedical Data base ( 1978–2008 ) with supplement of relevant websites , were search ed . There was no language restriction . The search es ended at March 2008 . We included r and omized and non-r and omized clinical trials , epidemiological studies ( cohort and case-control ) and a meta- analysis . We excluded case series , case reports , in vitro and animal studies . Outcomes were measured with estimation of relative risk , hazard or odd ratios , with 95 % confidence interval . Results Forty-three epidemiological studies , four r and omized trials and one meta- analysis were identified . The overall quality of these studies was evaluated as good or moderate . While some evidence suggests that green tea has beneficial effects on gastrointestinal cancers , the findings are not consistent . Conclusion Green tea may have beneficial effects on cancer prevention . Further studies such as large and long term cohort studies and clinical trials are warranted In systematic review s , meta‐analyses are routinely applied to summarize the results of the relevant studies for a specific research question . If one can assume that in all studies the same true effect is estimated , the application of a meta‐ analysis with common effect ( commonly referred to as fixed‐effect meta‐ analysis ) is adequate . If between‐ study heterogeneity is expected to be present , the method of choice is a meta‐ analysis with r and om effects . The widely used DerSimonian and Laird method for meta‐analyses with r and om effects has been criticized due to its unfavorable statistical properties , especially in the case of very few studies . A working group of the Cochrane Collaboration recommended the use of the Knapp‐Hartung method for meta‐analyses with r and om effects . However , as heterogeneity can not be reliably estimated if only very few studies are available , the Knapp‐Hartung method , while correctly accounting for the corresponding uncertainty , has very low power . Our aim is to summarize possible methods to perform meaningful evidence syntheses in the situation with only very few ( ie , 2‐4 ) studies . Some general recommendations are provided on which method should be used when . Our recommendations are based on the existing literature on methods for meta‐ analysis with very few studies and consensus of the authors . The recommendations are illustrated by 2 examples coming from dossier assessment s of the Institute for Quality and Efficiency in Health Care Aims : With the increase in the number of systematic review s available , a logical next step to provide decision makers in healthcare with the evidence they require has been the conduct of review s of existing systematic review s. Syntheses of existing systematic review s are referred to by many different names , one of which is an umbrella review . An umbrella review allows the findings of review s relevant to a review question to be compared and contrasted . An umbrella review 's most characteristic feature is that this type of evidence synthesis only considers for inclusion the highest level of evidence , namely other systematic review s and meta-analyses . A methodology working group was formed by the Joanna Briggs Institute to develop method ological guidance for the conduct of an umbrella review , including diverse types of evidence , both quantitative and qualitative . The aim of this study is to describe the development and guidance for the conduct of an umbrella review . Methods : Discussion and testing of the elements of methods for the conduct of an umbrella review were held over a 6-month period by members of a methodology working group . The working group comprised six participants who corresponded via teleconference , e-mail and face-to-face meeting during this development period . In October 2013 , the methodology was presented in a workshop at the Joanna Briggs Institute Convention . Workshop participants , review authors and method ologists provided further testing , critique and feedback on the proposed methodology . Results : This study describes the methodology and methods developed for the conduct of an umbrella review that includes published systematic review s and meta-analyses as the analytical unit of the review . Details are provided regarding the essential elements of an umbrella review , including presentation of the review question in a Population , Intervention , Comparator , Outcome format , nuances of the inclusion criteria and search strategy . A critical appraisal tool with 10 questions to help assess risk of bias in systematic review s and meta-analyses was also developed and tested . Relevant details to extract from included review s and how to best present the findings of both quantitative and qualitative systematic review s in a reader friendly format are provided . Conclusions : Umbrella review s provide a ready means for decision makers in healthcare to gain a clear underst and ing of a broad topic area . The umbrella review methodology described here is the first to consider review s that report other than quantitative evidence derived from r and omized controlled trials . The methodology includes an easy to use and informative summary of evidence table to readily provide decision makers with the available , highest level of evidence relevant to the question posed Evidence -based medicine represents the combination of the best available clinical research evidence with clinical experience and expertise and the needs and expectations of patients . Evidence -based medicine as a concept has been available for years , but it has become increasingly important over the last decade . Some evidence has suggested that it began as early as the ancient Chinese medicine practice s , while other evidence has indicated its origins were in postrevolutionary France with the systematic patient observations of Pierre Louis1 . Gordon Guyatt led a group at McMaster University in the early 1990s that introduced many of the current concepts of evidence -based medicine . This led to a major increase in interest in the area . One paper had been published in the literature in 1992 , but by 1998 over a thous and manuscripts had been published in the field1 . Evidence -based medicine utilizes the best available research evidence . In the hierarchy of medical evidence , systematic review s including meta-analyses represent the highest form of evidence if inclusion is limited to Level-I or II studies ( Table I ) . Systematic review s of Level-III or IV observational studies can be performed , but they represent Level-III or IV evidence . Frequently , in orthopaedics , systematic review s or meta-analyses may not be available and clinicians may need to rely upon r and omized controlled trials , cohorts , case-control studies , case series , or , in some areas , expert opinion . Orthopaedists may not yet recognize this hierarchy . During the 2005 Annual Meeting of the American Orthopaedic Association ( AOA ) , the audience was asked the question : “ Findings from which type of study design are most likely to influence your clinical practice ? ” The responses indicated that a r and omized controlled study design was used by 49 % ; a systematic review and /or meta- analysis of Level-I studies , by 44 % ; expert opinion , by 5 % ; and case series , by 3 % . View this table : TABLE I Medical Evidence Hierarchy At a symposium Background : Lipid-lowering treatment with statins has proven to be effective in reducing cardiovascular events and mortality . In daily practice , however , adherence to medication is often low and this compromises the therapeutic effect . The aim of this study was to assess the effectiveness of an electronic reminder device ( ERD ) with or without counseling to improve refill adherence and persistence for statin treatment in non-adherent patients . Methods : A multicenter , community pharmacy-based , r and omized controlled trial was conducted in 24 pharmacies in the Netherl and s among patients with pre-baseline refill adherence rates between 50 and 80 % . Eligible patients aged 65 years or older were r and omly assigned to 1 of 3 groups : ( 1 ) counseling with an ERD ( n = 134 ) , ( 2 ) ERD with a written instruction ( n = 131 ) , and a ( 3 ) control group that received the usual treatment ( n = 134 ) . Main outcome measure : refill adherence to statin treatment for a 360-day period after inclusion ( PDC360 ) . Patients with a refill rate ≥80 % were considered adherent . The effect among subgroups was also assessed . Results : There were no relevant differences at baseline . In the counseling with ERD group 54 of 130 eligible patients received the counseling with ERD . In the ERD group , 117 of 123 eligible patients received the ERD . The proportions of adherent patients in the counseling with ERD-group ( 69.2 % ) and in the ERD group ( 72.4 % ) were not higher than in the control group ( 64.8 % ) . Among women using statins for secondary prevention , more patients were adherent in the ERD group ( 86.1 % ) than in the control group ( 52.6 % ) ( p < 0.005 ) . In men using statins for secondary prevention the ERD was found to have no effect . Conclusion : In this r and omized controlled trial , no statistically significant improvement of refill adherence was found if an ERD was used with or without counseling . However , in a subgroup of women using statins for secondary prevention  the ERD did improve adherence significantly OBJECTIVES : Gastroesophageal reflux disease can be divided into three categories : nonerosive GERD ( NERD ) , erosive GERD ( ERD ) , and Barrett´s esophagus . A shift among these categories rarely occurs . The aim of the present study was to eluci date potential patient-associated risk factors associated with ERD . METHODS : A total of 6,215 patients with troublesome heartburn were recruited to a large , prospect i ve , multicenter open cohort study comprising an initial treatment phase and a 5-yr follow-up phase . Each center planned to recruit an equal number of patients with NERD and ERD . All patients underwent an interview based on st and ardized question naires , a physical examination , and endoscopy with biopsies . Data were analyzed by multiple logistic regression analysis . RESULTS : Risk factor analysis was performed on 5,289 patients ( NERD : n = 2,834 ; ERD : n = 2,455 ) , which was the intent-to-treat population excluding patients with suspected/proven complicated reflux disease . Stepwise regression analysis identified the following independent predictors of ERD : male gender , overweight , regular use of alcohol , a history of GERD > 1 yr , and smoker or ex-smoker . A higher level of education and a positive Helicobacter pylori ( H. pylori ) status were associated with a lower risk of ERD . CONCLUSIONS : Some patient-associated factors increase the risk of erosive esophagitis as opposed to nonerosive reflux disease . However , no single factor or combination of factors is capable of predicting mucosal damage with clinical ly sufficient certainty . Thus , endoscopy is still required in all GERD patients if valid information on the state of the esophageal mucosa is needed AIMS To analyse the effect on systematic review s in diabetes interventions of including only trials that are indexed in medline , and to assess the impact of adding trials from other data bases and the grey literature . METHODS All systematic review s of diabetes interventions which included a meta- analysis of r and omized controlled trials , and were published since 1996 , were selected . The impact on the meta- analysis of including only those trials indexed in medline , and the effect of then adding trials from other sources , was assessed . Where possible this was measured quantitatively , by redoing the meta- analysis , otherwise a qualitative estimate was made . RESULTS Forty-four systematic review s met our inclusion criteria . There were 120 articles reporting trial data which were not indexed in medline . These came from 52 % of the review s. In 34 % of the review s , basing a meta- analysis on a search of only medline would miss trials that could affect the result . Sources of non- medline data which had the biggest effect on the meta-analyses were journal articles from central and embase ( mainly in Diabetes , Nutrition and Metabolism ) and unpublished data ( mainly from industry ) . The exceptions were journal articles on herbal medicine , mostly indexed in Chinese language data bases . CONCLUSIONS A search of only the medline data base is insufficient for systematic review s of diabetes , because in about 34 % of review s the missed trials could affect the results of the meta- analysis . It is recommended that central ( on the Cochrane Library ) also be search ed . Scanning meeting abstract s , and seeking unpublished data are also recommended if the intervention has only recently been introduced Background The prevalence of overweight and obesity is high amongst healthcare professionals and there is growing interest in delivering weight loss interventions in the workplace . We conducted a systematic review to ( i ) examine the effectiveness of workplace-based diet and /or physical activity interventions aim ed at healthcare professionals and to ( ii ) identify and describe key components of effective interventions . Seven electronic data bases were systematic ally search ed . Results Thirteen r and omised controlled trials met the inclusion criteria , of which seven had data available for meta- analysis . Where meta- analysis was possible , studies were grouped according to length of follow-up ( < 12 months and ≥12 months ) and behavioural target ( diet only , physical activity only or diet and physical activity ) , with outcome data pooled using a weighted r and om effects model . Nine studies reported statistically significant ( between-group ) differences . Four studies reported being informed by a behaviour change theory . Meta- analysis of all trials reporting weight data demonstrated healthcare professionals allocated to dietary and physical activity interventions lost significantly more body weight ( −3.95 Kg , [ 95 % CI −4.96 to- 2.95 Kg ] ) than controls up to 12 months follow up . Conclusions Workplace diet and /or physical activity interventions targeting healthcare professionals are limited in number and are heterogeneous . To improve the evidence base , we recommend additional evaluations of theory-based interventions and adequate reporting of intervention content Introduction Vitamin D has potential benefits for extraskeletal health . These could include an anti-inflammatory effect as well as a reduction in endothelial dysfunction . We aim to provide quality evidence for the hypothesis that supplementation with vitamin D will improve endothelial function ( EF ) , possibly through the abrogation of systemic inflammation . Methods and analysis We will conduct a systematic review of all r and omised controlled trials on  vitamin D supplementation and EF lasting 12 weeks or more . The search will cover the period 2000–2015 and include studies that describe direct measures of EF  , markers of endothelial cell ( EC ) activation  and if concurrently reported , indicators of systemic inflammation  . Study selection will follow the Preferred Reporting Items for Systematic Review s and Meta-Analyses ( PRISMA ) guidelines and study quality will be assessed by the Jadad score in addition to an evaluation of allocation concealment and data analysis . If sufficient data are available , a meta- analysis will be conducted . The effect sizes will be generated using Hedges ’ g score , for both fixed and r and om effect models . I2 statistics and Galbraith plots will be used to assess heterogeneity and identify their potential sources . Potential publication and small sample size bias will be assessed by visual inspections of funnel plots and also Egger 's test . Meta-regression analysis ( if feasible ) will be conducted with restricted maximum likelihood ( REML ) estimation method , controlling for potential confounders ( demographics , study methods , location , etc ) . A backward elimination process will be applied in the regression modelling procedure . Subgroup analysis , conditional on number of studies retrieved and their sample size , will be stratified on participant disease category , total dose administered , degree of 25(OH)D change and type of supplement used . Ethics and dissemination Formal ethical approval is not required as primary data will not be collected . The results will be disseminated through a peer- review ed publication , conference presentation and the popular press . Trial registration number International Prospect i ve Register for Systematic Review s ( PROSPERO ) number CRD42014013523 & NA ; Physical therapists seeking to use evidence to guide their practice may have limited time to read research reports . One way to reduce the time required to identify and read about the research that is relevant to a particular clinical question is to read a systematic review that summarizes multiple studies . This paper explains the process that is used to conduct systematic review s , which includes the establishment of a protocol , comprehensive search ing , appraisal of the quality of the included studies , data extraction and meta analysis , and consideration of the clinical and research implication s of the findings . We also consider how the reader of a systematic review can determine whether the review is likely to provide an unbiased ( believable ) estimate of the treatment effect . A systematic review of r and omized trials of a  cardiopulmonary physical therapy intervention is used as an example . The issue of appraisal of quality is then discussed further , with a demonstration of how one vali date d tool for quality appraisal ‐‐the PEDro scale‐‐can be used to evaluate a r and omized trial in cardiopulmonary physical therapy OBJECTIVES To assess the type of evidence that supported our management of surgical patients . DESIGN Retrospective audit . SETTING Teaching hospital , Republic of Irel and . PATIENTS All 222 patients admitted by two surgical teams during one month . Patients admitted for diagnostic procedures were included if they were treated as a result . MAIN OUTCOME MEASURES Diagnosis and treatment were established from the notes . Evidence for each intervention was then sought in MEDLINE 1986 - 1999 , Best Evidence 1991 - 1999 , and the Cochrane Data base of Systematic Review s Issue 3 , 1999 , and grade d into one of five categories : systematic review , meta- analysis , r and omised controlled trial , prospect i ve study , or retrospective study . RESULTS Treatment was supported by systematic review in 14 , by meta- analysis in 12 , by r and omised controlled trial in 75 , by prospect i ve studies in 55 , by retrospective studies in 58 , and by no evidence in 8 . CONCLUSIONS Everyday surgical practice in our unit is supported by good quality evidence from recent publications AIMS Pain and anxiety are commonly reported among those undergoing orthopaedic surgery . Improvement in anxiety and pain control might be achieved by supplementing st and ard care with psychological interventions . However , the effectiveness of adjunctive psychosocial interventions in anxiety and pain control have not been addressed sufficiently by previous systematic review s in orthopaedic surgeries . The present study aim ed to assess the effectiveness of adjunctive psychosocial techniques to improve perioperative clinical care in orthopaedic surgery , to identify the most effective intervention types and to evaluate potential moderators . METHODS We will perform a systematic review and meta- analysis to address the study aims . PubMed , PsycINFO , CINAHL and ProQuest Dissertations & Theses will be search ed between 1980 and 2015 . Prospect i ve controlled clinical trials completed in adults , contrasting st and ard care and st and ard care supplemented with psychosocial methods  , will be eligible for inclusion . Effectiveness will be assessed through the outcomes of postoperative pain intensity , analgesic requirement , perioperative anxiety , quality of life and postoperative recovery . The results of a r and om-effect meta- analysis will be reported . To aid implementation of best practice , moderating effects of the type and timing of psychosocial intervention , type of surgical intervention and type of anaesthesia will be evaluated through meta-regression . Sensitivity analyses and subgroup contrasts will follow as necessary . DISCUSSION Recommendations will be made to improve medical care in orthopaedic procedures . The quality of evidence will be rated using GRADE criteria . Copyright © 2016 John Wiley & Sons , CONTEXT The findings of systematic review s ( SRs ) and meta-analyses ( MAs ) are used for clinical decision making . The European Association of Urology has committed increasing re sources into the development of high quality clinical guidelines based on such SRs and MAs . OBJECTIVE In this paper , we have summarised the process of conducting SRs for underpinning clinical practice guidelines under the auspices of the European Association of Urology Guidelines Office . EVIDENCE ACQUISITION The process involves explicit methods and the findings should be reproducible . When conducting a SR , the essential first step is to formulate a clear and answerable research question . An extensive literature search lays the foundation for evidence synthesis . Data are extracted independently by two review ers and any disagreements are resolved by discussion or arbitration by a third review er . EVIDENCE SYNTHESIS In SRs , data for particular outcomes in individual r and omised controlled trials may be combined statistically in a meta- analysis to increase power when the studies are similar enough . Biases in studies included in a SR/MA can lead to either an over estimation or an under estimation of true intervention effect size , result ing in heterogeneity in outcome between studies . A number of different tools are available such as Cochrane Risk of Bias assessment tool for r and omised controlled trials . In circumstances where there is too much heterogeneity , or when a review has included nonr and omised comparative studies , it is more appropriate to conduct a narrative synthesis . The GRADE tool for assessing quality of evidence strives to be a structured and transparent system , which can be applied to all evidence , regardless of quality . A SR not only identifies , evaluates , and summarises the best available evidence , but also the gaps to be targeted by future studies . CONCLUSIONS SRs and MAs are integral in developing sound clinical practice guidelines and recommendations . PATIENT SUMMARY Clinical practice guidelines should be evidence based , and systematic review s and meta-analyses are essential in their production . We have discussed the key steps of conducting systematic review s and meta-analyses in this paper This article describes approaches for planning , dealing , and analyzing heterogeneity in a systematic review of complex interventions . Approaches aim to generate a priori hypotheses of the mechanism of action of a complex intervention to identify the key variables that might contribute to variation among studies and guide statistical analysis . In addition to characteristics related to the population , intervention , and outcomes , we describe study -related variables , such as the way the interventions have been implemented and the context and conduct of studies . These approaches will guide review ers planning a meta- analysis and provide a rationale for not meta-analyzing data if there is too much variability . Potential difficulties in applying meta-analytical techniques to examine statistical association among study results and sources of potential heterogeneity are described ; these include the selection of a fixed or r and om-effects model , the risk of multiple testing and confounding when studies include different aspects of a complex intervention or different sub sample s of the intended participant pool
Relative to a non-diet control , IF and ERD are effective for the improvement of circulating TC , LDL-C , and TG concentrations , but have no meaningful effects on HDL-C concentration .
The present results suggest that these dietary practice s are a means of enhancing the lipid profile in humans
OBJECTIVES To the best of our knowledge , no systematic review and meta- analysis has evaluated the cholesterol-lowering effects of intermittent fasting ( IF ) and energy-restricted diets ( ERD ) compared with control groups .
The aim of this review and meta- analysis was to summarize the effects of controlled clinical trials examining the influence of IF and ERD on lipid profiles .