Cognitive behavioural therapy for adults with overweight or obesity

Objectives

This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

To assess the effects of cognitive behavioural therapy for weight management in adults with overweight or obesity.

Background

Description of the condition

Overweight and obesity are defined as abnormal or excessive accumulation of body fat, which may harm health (WHO 2019a; WHO 2019b). For adults, a body mass index (BMI) ≥ 25 kg/m² is considered overweight, and BMI ≥ 30 kg/m² is obese (WHO 2021a). The prevalence of overweight and obesity in adults is increasing, with the average BMI of adults rising from 22 kg/m² in 1975 to 24 kg/m² in 2014 (NCD‐RisC 2017). In 2016, 1.9 billion adults worldwide were overweight. Of those classified as overweight, 650 million were obese, meaning that globally, 39% of adults were overweight, and 13% were obese (WHO 2021b). By 2030, it is estimated that over one billion adults will be living with obesity (NCD‐RisC 2017; WOF 2022).

Overweight or obesity is associated with increased all‐cause mortality (GBMC 2016; Petrelli 2021). It may also increase the risk of a range of chronic diseases, including cardiovascular disease (e.g. hypertension, myocardial infarction, and stroke (Opio 2020)), certain types of cancer (e.g. breast, colon, gallbladder, kidney, liver, and ovarian (Bhaskaran 2014; He 2021)), metabolic diseases (e.g. type 2 diabetes mellitus and fatty liver disease (Bell 2014; Lotta 2015)), musculoskeletal disease (e.g. osteoarthritis (Blüher 2019)), neurocognitive disorders (e.g. Alzheimer disease and other dementias (Flores‐Cordero 2022; Qu 2020)), psychological disorders (e.g. anxiety, behavioural problems, and depression (Pereira‐Miranda 2017)), and respiratory disease (e.g. asthma and sleep apnoea (Peters 2018)). A modelling study revealed that individuals with obesity have a significantly lower active life expectancy (Jia 2022). Obesity may also contribute to reduced quality of life, job loss, lower productivity, and social disadvantages (Blüher 2019). When considering diversity, factors such as sex, race, religion, and disability often come to mind; however, weight and body size are also important aspects. Yet, many people overlook weight and body size when addressing diversity. Weight discrimination experienced by individuals with obesity is common, and its negative consequences are highly relevant societal issues (Spahlholz 2016). In summary, being overweight or obese impairs both physical and psychological well‐being. Therefore, it is essential to carefully select evidence‐based treatment strategies for adults who are overweight or obese.

Overweight and obesity have a wide range of drivers and determinants. Genetics, biology, healthcare access, psychology, mental health, sociocultural factors, equity, ultra‐processed foods, economics, commercial factors, and environmental factors contribute to overweight and obesity (Gunstad 2020; WOF 2022). These factors interact with each other in complex ways. For example, weight gain is usually associated with a restricted physical activity capacity. The psychological effects of weight bias and obesity stigmatisation increase, and high‐caloric palatable foods are more frequently used as a coping strategy, thus leading to a vicious cycle of further weight gain (Blüher 2019). In some affected people, psychological factors, including stress and weight bias, lead to behavioural addiction to eating, which may also contribute to the same vicious weight gain cycle. As a psychological co‐factor in obesity development, an eating addiction is more typical than a food addiction (Blüher 2019; Hebebrand 2014).

Description of the intervention

Cognitive behavioural therapy (CBT) describes a family of psychological interventions that combines principles of both behavioural and cognitive therapy. The historical precursors to CBTs were behaviour theories that ignored or downplayed the role of cognition in influencing behaviour, now sometimes referred to as behavioural therapies. Traditional CBTs focus on changing behaviours and altering thoughts and beliefs (Wenzel 2021). Over the past decades, a set of new behavioural and cognitive methods have emerged, based on contextual concepts that focus more on function, rather than form (e.g. purposes and consequences of thought process instead of a change of thought content), and focus more on acceptance and mindfulness, rather than a dominant focus on cognitive and behavioural modification and symptom reduction (McCracken 2022; Wenzel 2021). CBTs also vary in the way they focus on thoughts and behaviours within the therapeutic intervention, and the treatment processes they target. CBTs have been demonstrated to be effective for a range of conditions, such as anxiety disorders (James 2020), asthma (Kew 2016), depression (Ijaz 2018; Orgeta 2022), eating disorders (Hay 2009), and insomnia (Edinger 2021; Liu 2022).

International guidelines (e.g. guidelines of the National Institute for Health and Care Excellence, Scottish Intercollegiate Guidelines Network, and American Association of Clinical Endocrinologists and American College of Endocrinology) recommend a course of comprehensive lifestyle interventions as the first line treatment for weight loss in adults with overweight or obesity (Mackenzie 2020; Semlitsch 2019). Lifestyle interventions are composed of three core components: a reduced‐calorie meal plan, increased physical activity, and behavioural therapies that enhance adherence to prescriptions for a reduced‐calorie diet and increased physical activity (Semlitsch 2019). Since many so‐called behavioural interventions include both cognitive and behavioural techniques to facilitate adherence to diet and activity goals, the term cognitive behavioural therapy is sometimes used interchangeably with behavioural therapy (Fabricatore 2006; Van Dorsten 2011; Wenzel 2021).

CBTs for weight management focus on cognitive and behavioural conceptualisations of weight gain and loss (i.e. the importance of thoughts, and their impact on behaviours in the process that maintains the target problem). Cognitive approaches are used to increase awareness of negative thought processes that influence body weight. Two commonly used techniques are problem‐solving alternatives to negative self‐talk, and cognitive restructuring to challenge the validity of negative self‐attributions (Fabricatore 2006; Van Dorsten 2011). Commonly used techniques to build behavioural skills include: establishing objective treatment goals, self‐monitoring of overeating triggers, making changes to the environment to support positive changes, using stimulus control techniques to cue the occurrence of desired behaviours, and relapse‐prevention planning (Van Dorsten 2011). CBTs, used in conjunction with motivational interviewing strategies, might also improve change readiness (Barrett 2018). CBTs have often been combined with other approaches, including mindfulness methods, acceptance‐based procedures, recentering, cognitive defusion, values, and psychological flexibility processes (Lawlor 2020).

Adverse effects of the intervention

The adverse effects of CBTs are not widely discussed or reported (Jacob 2018; LeBlanc 2018). The US Preventive Services Task Force (US‐PSTF) conducted a systematic review to investigate the adverse effects of behavioural weight‐loss interventions (LeBlanc 2018). They found that harms from interventions were sparsely reported, and the potential harms included increased risk for fractures, serious injuries resulting from increased physical activity, and an increased risk for eating disorders, weight stigma, and weight fluctuation (LeBlanc 2018; USPSTF 2018). The US‐PSTF concluded that the included studies demonstrated no serious harm, and most studies found no difference in the rate of adverse events between intervention and control groups (USPSTF 2018).

How the intervention might work

Because overweight and obesity are related to psychological factors, psychological interventions are key elements to engage adults with overweight or obesity in lifestyle modification, and motivate them to achieve weight loss with the help of multidisciplinary teams (Castelnuovo 2017). CBTs for weight management usually use a combination of behavioural techniques to modify behaviour, and cognitive therapy techniques to find and change dysfunctional beliefs, thinking patterns, and other underlying cognitive vulnerabilities that constitute a barrier to behaviour change. CBTs have often been combined with other approaches (e.g. mindfulness, acceptance, and commitment therapy) to encourage people with overweight or obesity to accept aversive internal experiences (e.g. food addiction and behavioural fatigue) rather than remove them. Increased present‐moment, non‐judgemental awareness and psychological flexibility might help people identify internal and external cues to overeat, and change behavioural responses to be more congruent with their values. Fostering a compassionate attitude towards oneself could also help prevent losing confidence following lapses (Lawlor 2020).

Why it is important to do this review

Jacob and colleagues conducted a meta‐analysis to investigate the effects of CBT‐based weight loss interventions on weight loss, cognitive restraint, emotional/binge‐eating, and depressive/anxiety symptoms in adults with overweight or obesity (Jacob 2018). However, this study combined active treatments (including at least one component related to nutrition, physical activity, or behaviour change techniques, or a combination), and inactive treatments (waiting list or usual care) into a single comparator.

Numerous randomised controlled trials (RCTs) focusing on CBT for weight management in adults with overweight or obesity have emerged in recent years, owing to the increasing popularity of CBT. To date, no published Cochrane Review or protocol has compared CBT for weight management with other treatments for adults with overweight or obesity. Consequently, a comprehensive Cochrane Review on the utilisation of CBT for weight management in adults with overweight or obesity is essential for guiding decision‐making processes for affected individuals, clinicians, and other stakeholders.

Objectives

To assess the effects of cognitive behavioural therapy for weight management in adults with overweight or obesity.

Methods

Criteria for considering studies for this review

Types of studies

We will include randomised controlled trials (RCTs) that meet our inclusion criteria. We will exclude cross‐over trials, as they are generally unsuitable for assessing longer‐term outcomes in chronic diseases, and tend to focus on interventions with transient effects on stable, chronic conditions during the study period (Higgins 2022c). We will also exclude quasi‐randomised studies, to reduce sources of potential heterogeneity.

We will include studies reported as full text, those published as abstract only, and unpublished data when it is possible to establish their eligibility for inclusion, when data are limited. There will be no language restrictions.

Types of participants

Participants will be adults, classified as overweight or obese, regardless of co‐morbidity (e.g. diabetes, hypertension, or dyslipidaemia). If we identify studies in which only a subset of participants is relevant to this review, we will include such studies if data are available separately for the relevant subset, or if the majority of participants (> 80%) meet the inclusion criteria.

Diagnostic criteria for overweight and obese adults

Participants will be adults (18 years of age and older) with a body mass index (BMI) between 25 kg/m² and 29.9 kg/m², classified as overweight, and those with a BMI of 30 kg/m² or greater, classified as obese.

Types of interventions

We plan to investigate the following comparisons of intervention versus control/comparator.

Intervention

Cognitive behavioural therapy (CBT) has been used as a broad label that can include a variety of interventions. It usually uses a combination of behavioural techniques (e.g. stimulus control, self‐monitoring, and goal setting) to modify behaviour, and cognitive therapy techniques (e.g. alternative problem‐solving and cognitive restructuring) to find and change dysfunctional beliefs, thinking patterns, and other underlying cognitive vulnerabilities that constitute a barrier to behaviour change. CBT is sometimes integrated with other treatments (e.g. motivational interviewing), or combined with so‐called, third‐wave components, such as mindfulness, acceptance, and commitment therapy.

For the aims of this review, any CBT‐based intervention that focusses on cognitive and behavioural conceptualisations of weight management (i.e. the importance of thoughts and their impact on behaviours in the process that maintains the target problem) will be eligible for inclusion. The intervention should go beyond the techniques defined as purely behavioural, such as self‐monitoring, stimulus control, and goal setting. We will ascertain the role of different subtypes of CBT interventions by analysing them separately in a subgroup analysis.

Comparator

We planned to include studies that compared CBT to non‐CBT interventions.

• No treatment or waiting list control

• Usual care

• Behavioural techniques only

To establish fair comparisons, concomitant interventions will have to be identical in both the intervention and comparator groups. If a study includes multiple arms, we will include any arm that meets the inclusion criteria for this review.

Minimum duration of intervention

There is no minimum duration of the intervention.

Minimum duration of follow‐up

Minimum duration of follow‐up will be six months from baseline.

We will define extended follow‐up periods (open‐label extension studies) as a follow‐up of participants once the original trial, as specified in the trial protocol, has been terminated.

Summary of specific exclusion criteria

• Trials designed to treat eating disorders

• Trials with a follow‐up duration of less than six months from baseline

Types of outcome measures

We will not exclude a study if it fails to report one or several of our primary or secondary outcome measures. We will only exclude studies if none of the outcomes relevant to this review were measured, provided there is supporting evidence for this (e.g. contact with trial authors, access to the original protocol, etc.).

The choice of outcome measures is based on the core outcome set (COS) determined for behavioural weight management interventions for adults with overweight and obesity (Mackenzie 2020). This COS was developed by conducting a systematic review and a two‐stage Delphi study, during which it was determined which outcome measures in behavioural weight management interventions research should be requested during research studies.

Primary outcomes

• Changes in body weight, BMI, or both

• Quality of life

• Adverse events

Secondary outcomes

• Participant satisfaction

• Diabetes status

• Depressive symptoms

• Self‐confidence and self‐esteem

Method of outcome measurement

• Changes in body weight (kg), BMI (kg/m²), or both, measured but not self‐reported

• Quality of life: measured by instruments judged to possess adequate validity, e.g. EQ‐5D (EuroQol ‐ 5 dimension, a descriptive instrument used to assess health‐related quality of life), or SF‐36 scores (36 Item Short Form Health Survey, another widely used instrument used to evaluate health‐related quality of life)

• Adverse events: any treatment‐related harms that occurred during or after the intervention, such as fractures and serious injuries, resulting from increased physical activity (USPSTF 2018)

• Participant satisfaction: measured and defined in included trials, e.g. measured by questionnaires, such as the Outcomes and Experiences Questionnaire, adapted to suit weight management services (Gibbons 2015), and NHS Friends and Family Test (NHS 2019)

• Diabetes status: mean change in HbA1c levels of participants with type 2 diabetes mellitus (Mackenzie 2020)

• Changes in depressive symptoms: assessed continuously by validated self‐report questionnaires, such as the Beck Depression Inventory (Beck 1988), and the Patient Health Questionnaire‐9 (Kroenke 2003)

• Changes in self‐confidence and self‐esteem scores: assessed continuously by validated self‐report questionnaires, such as the Warwick‐Edinburgh Mental Wellbeing Scale (Tennant 2007)

Timing of outcome measurement

• Changes in measured body weight (kg), BMI, (or both), quality of life score, depression, self‐confidence and self‐esteem score: measured at baseline, and any time point on or after six‐month follow‐up. We will include the longest reported follow‐up period in the main analysis if multiple time points are reported for these outcomes.

• Adverse events: measured at any time after participants were randomised to the intervention and comparator groups

• Participant satisfaction: measured at any time point on or after six‐month follow‐up. We will include the longest reported follow‐up period in the main analysis if multiple time points are reported for these outcomes.

Minimally important difference

​​​​​​If possible, we will compare the pooled estimates with the minimally important difference (MID) values for continuous outcomes to aid interpretation. We will use published MIDs when available. When multiple MID estimates are available for an outcome, we will use the smallest validated MID.

Search methods for identification of studies

Electronic searches

We will search the following sources from the inception of each database to the date of search, and will place no restrictions on the language of publication:

• Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library Ovid (the latest issue);

• MEDLINE Ovid; MEDLINE ALL (1946 to daily update);

• APA PsycINFO Ovid (1806 to present);

• ClinicalTrials.gov (www.clinicaltrials.gov);

• World Health Organization International Clinical Trials Registry Platform (ICTRP; www.who.int/trialsearch/).

We will not include Embase in our search, as RCTs indexed in Embase are now prospectively added to CENTRAL via a highly sensitive screening process (Cochrane 2020). For detailed search strategies, see Appendix 1.

Searching other resources

We will attempt to identify other potentially eligible studies or ancillary publications by searching the reference lists of included studies, and systematic reviews and meta‐analyses identified through our database searches. We will also contact the authors of the included studies to obtain additional information on the retrieved studies, and establish whether we may have missed further studies.

Data collection and analysis

Selection of studies

We will consider using Cochrane's Screen4Me workflow to help assess the search results. Screen4Me comprises three components: known assessments – a service that matches records in the search results to records that have already been screened in Cochrane Crowd, and been labelled as an RCT or not an RCT; the RCT classifier – a machine learning model that distinguishes RCTs from non‐RCTs; and if appropriate, Cochrane Crowd – Cochrane’s citizen science platform, where the Crowd help to identify and describe health evidence. Detailed information regarding evaluations of the Screen4Me components can be found in: Marshall 2018; McDonald 2017; Noel‐Storr 2018; Thomas 2017. Two review authors (TY, MM) will independently screen the abstract, title, or both, of all records remaining after the Screen4Me workflow, to determine which studies we should assess further.

We will obtain the full text of all potentially relevant records. We will resolve disagreements through consensus, or by recourse to a third review author (CZ). If we cannot resolve a disagreement, we will categorise the study as 'awaiting classification', and will contact the study authors for clarification. We will present a PRISMA flow diagram to show the process of study selection (Page 2021). We will list all articles excluded after a full‐text assessment in a characteristics of excluded studies table, and will provide the reasons for exclusion (Page 2021). We will use the latest version of Covidence software for study selection (Covidence).

To screen non‐English language papers for eligibility, we will start with Google Translate or Baidu Translate. If needed, we will seek translators in our university networks or Cochrane Engage to assist with assessing the eligibility of studies, and if eligible, to assist with data extraction by native speakers.

Data extraction and management

For studies that fulfil our inclusion criteria, two review authors (TY, MM) will independently extract key information on participants, interventions, and comparators. We will extract the following data from reports.

• Methods

  • Study design

• Participants

  • Inclusion and exclusion criteria

  • Participant details, baseline characteristics (e.g. age, gender distribution, ethnicity, baseline body weight status, co‐morbidity (e.g. diabetes, hypertension, or dyslipidaemia))

  • The number of participants by study and by study arm

• Interventions and comparisons, according to the Template for intervention description and replication (TIDieR) checklist (Hoffmann 2014; Hoffmann 2017)

  • Name of the intervention

  • Why: rationale, theory or goal of the elements essential to the intervention

  • What: physical or informational materials used in the intervention; procedures, activities, or processes used in the intervention

  • Who provided: expertise, background and specific training given

  • How: describe modes of delivery

  • Where: describe the location where the intervention occurred, including infrastructure and features

  • When/how much: the number of times the intervention was delivered over a period of time

  • Tailoring: describe if personalisation or adaptations were planned

  • Modifications: during the course of the study

  • How well: measurements of adherence or fidelity

• Outcomes:

  • Definitions of relevant outcomes, method and timing of outcome measurement, and any relevant subgroups to the review

• Study dates (start date to end date; if dates are not available, report as such)

• Study settings and country, language of publication, and study identifier

• Study funding sources

• Declarations of interest by primary investigators

These data will be reported in the characteristics of included studies tables, in summary tables, and in the main text (see Table 1).

1. Summary of the characteristics of included studies.

Study ID	Study period	Country/setting	Characteristics of participants	Sample size (randomised)	Intervention	Comparison	Follow‐up
Author/Year

We will contact all authors of the included studies to enquire whether they would be willing to answer questions regarding their studies. We will document these communications. We will seek relevant missing information on the study from the primary study author(s), if required.

Dealing with duplicates and companion publications

In the event of duplicate publications, companion documents, or multiple reports of a primary study, we will maximise the information yield by collating all available data, and we will use the most complete data set aggregated across all known publications. We will list duplicate publications, companion documents, multiple reports of a primary study, and trial documents of included trials (such as trial registry information) as secondary references under the study ID of the included study. We will also list duplicate publications, companion documents, multiple reports of a study, and trial documents of excluded trials (such as trial registry information) as secondary references under the study ID of the excluded study.

Data from clinical trials registers

If data from included studies are available as study results in clinical trials registers, such as ClinicalTrials.gov, or similar sources, we will make full use of this information and extract the data. If there is also a full publication of the study, we will collate and critically appraise all available data. If the published and unpublished data do not match, we will ask the study authors for clarification. If we receive no response, we will present the discrepancies in the full‐review report. If an included study is labelled as completed in a clinical trial register, but no additional information (study results or publication, or both) is available, we will add this study to the characteristics of studies awaiting classification table.

Assessment of risk of bias in included studies

Two review authors (TY, MM) will independently assess the risk of bias in each study for the results of the main outcomes (those included in the summary of findings table, see below) using a recently developed revision of the Cochrane RoB 2 tool (Higgins 2022a). We will resolve disagreements by consensus or by consulting a third review author (CZ). If adequate information is not available from the publications, trial protocols, clinical study reports, or other sources, we will contact the study authors for more details, and to request missing data on risk of bias items. We will assess the risk of bias according to the following domains, focusing on the effect of assignment to the intervention at baseline.

• the randomisation process

• deviations from intended interventions

• missing outcome data

• measurement of the outcome

• selection of the reported results

Answers to signalling questions and supporting information will collectively lead to a domain‐level judgement of either low risk, some concerns, or high risk of bias. These domain‐level judgements will inform an overall risk of bias judgement for a single result in the form of (a) low risk, if all domains are judged as being low risk, (b) some concerns, if one or more domains are judged as being of some concerns, and (c) high risk, if one or more domains are judged as being high risk, or if four domains are judged of being of some concerns. We will provide a quote from the study report, together with a justification for our judgement in the risk of bias table. We will summarise the risk of bias judgements across different studies for each of the domains listed. We will aim to source trial registries, protocols, and analysis plans to assess selective reporting. Where information on the risk of bias relates to unpublished data or correspondence with a trialist, we will note this in the risk of bias table.

When considering treatment effects, we will take into account the risk of bias for the studies that contribute to that outcome. We will construct summary assessments of the risk of bias for each important outcome (across domains), within and across studies (Higgins 2022a).

We will use the RoB 2 Excel tool to manage the data supporting the answers to the signalling questions and risk of bias judgements (available at www.riskofbias.info/). All data will be publicly available as supplementary material in a public repository.

For cluster‐randomised clinical trials, we will consider an additional domain that specifically applies to the design of the cluster‐randomised clinical trial, RoB 2 Domain 1b, Bias arising from the timing of identification and recruitment of individual participants within clusters in relation to timing of randomisation. We will follow the suggested algorithm for reaching risk of bias judgements for bias arising from the timing of identification and recruitment of participants in a cluster‐randomised trial (Eldridge 2021). At the time of review preparation, we will use the most recent recommendations for assessing risk of bias in cluster‐randomised trials.

Measures of treatment effect

We will try to express dichotomous data as a risk ratio (RR), or Peto odds ratio (OR) when the outcome is a rare event (approximately less than 1% (Deeks 2022)), with 95% confidence intervals (CIs). For continuous outcomes measured on the same scale (e.g. weight loss in kg) we will estimate the intervention effect using the mean difference (MD) with 95% CIs. When data are pooled in studies that used different instruments to measure the same outcome, we plan to calculate standardised mean differences (SMDs) with 95% CIs, entering data presented as a scale with a consistent direction of effect, and multiplying the SMD by a standard deviation that is representative of the pooled studies, for example, the standard deviation (SD) from a well known scale used by several of the studies included in the analysis on which the result was based. We will express time‐to‐event data as a hazard ratio (HR) with 95% CIs.

Unit of analysis issues

We will take into account the level at which randomisation occurred, such as cluster‐randomised trials and multiple observations for the same outcome. If more than one comparison from the same study is eligible for inclusion in the same meta‐analysis, we will either combine groups to create a single pair‐wise comparison, or we will appropriately reduce the sample size so that the same participants do not contribute data to the meta‐analysis more than once (splitting the shared group into two or more groups). Although the latter approach offers some solutions for adjusting the precision of the comparison, it does not account for correlation arising from the inclusion of the same set of participants in multiple comparisons (Higgins 2022b).

We will attempt to re‐analyse cluster‐RCTs that did not appropriately adjust for potential clustering of participants within clusters in their analyses. The variance of intervention effects will be inflated by a design effect. Calculation of a design effect involves the estimation of an intracluster correlation coefficient (ICC), as specified in Chapter 23 of the Cochrane Handbook of Systematic Reviews for Interventions (Higgins 2022b). We will obtain estimates of ICCs by contacting study authors, or by imputing ICC values, using either estimates from other included studies that report ICCs, or external estimates from empirical research. We plan to examine the impact of clustering by performing sensitivity analyses.

Dealing with missing data

If possible, we will obtain missing data from the authors of the included studies. We will carefully evaluate important numerical data, such as screened, randomly assigned participants, as well as intention‐to‐treat, as‐treated, and per‐protocol populations, in our risk of bias assessments. For this, we will investigate attrition rates (e.g. dropouts, losses to follow‐up, and withdrawals), and we will critically appraise issues concerning missing data and the use of imputation methods (e.g. last observation carried forward). For our primary analyses, we will conduct available case analyses, considering these issues when assessing the risk of bias and the certainty of the evidence.

For studies in which the standard deviation (SD) of the outcome is not available at follow‐up, or we cannot recreate it, we will standardise by the mean of the pooled baseline SD from studies that reported this information.

Assessment of heterogeneity

In the event of substantial clinical or methodological heterogeneity, we will not report study results as the pooled effect estimate in a meta‐analysis.

We will take into account a visual examination of the variability in point estimates and the overlap in confidence intervals. We will use the I² statistic to estimate the degree of heterogeneity present among the trials in each analysis. If we identify substantial unexplained heterogeneity, we will report it and explore possible causes by prespecified subgroup analysis. We will use the rough guide to interpretation as outlined in Chapter 10 of the Cochrane Handbook, as follows (Higgins 2022b).

• 0% to 40%: might not be important

• 30% to 60%: may represent moderate heterogeneity

• 50% to 90%: may represent substantial heterogeneity

• 75% to 100%: considerable heterogeneity

We will avoid the use of absolute cutoff values, but interpret I² in relation to (a) the size and direction of effects, and (b) the strength of evidence for heterogeneity (e.g. P value from the Chi² test, or CI for I²).

Assessment of reporting biases

If we include 10 studies or more per comparison and outcome, we will use funnel plots to assess small‐study effects. Several explanations may account for funnel plot asymmetry, including true heterogeneity of effect with respect to study size, poor methodological design (and hence bias of small studies), and selective non‐reporting (Kirkham 2010). Therefore, we will interpret the results carefully (Sterne 2011).

Data synthesis

We plan to undertake a meta‐analysis, using the latest version of Review Manager, only if we judge the participants, interventions, comparisons, and outcomes to be sufficiently similar to ensure a result that is clinically meaningful (RevMan Web 2023). Unless good evidence shows homogeneous effects across studies of different methodological quality, we will primarily summarise data using a random‐effects model (Wood 2008). We will interpret random‐effects meta‐analyses with due consideration for the whole distribution of effects, and will present a confidence interval. We will perform statistical analyses according to the statistical guidelines presented in the Cochrane Handbook (Deeks 2022). When meta‐analysis is not possible, we will conduct alternative forms of synthesis, including the summary of effect estimates, the combination of P values, and vote counting, based on the direction of effects, as described in Chapter 12 of the Cochrane Handbook (McKenzie 2022).

Subgroup analysis and investigation of heterogeneity

We expect the following characteristics to introduce clinical heterogeneity, and we plan to carry out subgroup analyses for these, including an investigation of interactions (Altman 2003).

• Different types of CBT

  • We will analyse different kinds of CBT as different subgroups, such as manualised CBT programmes, CBT integrated with other treatments (for example, motivational interviewing), or combined with third‐wave components (mindfulness, acceptance, and commitment therapy).

• Modality of treatment

  • We will analyse CBT administered in individual or group sessions separately.

• Method of delivery

  • We will analyse CBT delivered face‐to‐face, or with other methods of delivery (online, telephone) separately.

• Duration of intervention

  • We will analyse different durations of intervention, e.g. < 3 months versus ≥ 3 months, < 6 months versus ≥ 6 months.

• Intensity of intervention

  • We will analyse different intensities of intervention, e.g. weekly versus biweekly/monthly sessions.

We will extract data at the longest follow‐up from each study. If we find a lack of consistency across studies, we will carry out a subgroup analysis for primary outcomes.

We will use the formal test for subgroup interactions in RevMan Web, acknowledging its limitations due to its observational nature and low power to detect differences with fewer than 10 studies per category (Higgins 2022b; RevMan Web 2023).

Sensitivity analysis

We plan to perform sensitivity analyses to explore the influence of the following factors (when applicable) on effect sizes

• Restricting the analysis to studies at an overall low risk of bias

• Cluster‐randomised studies

• Studies without imputed data

Summary of findings and assessment of the certainty of the evidence

We will present the overall certainty of the evidence for each outcome specified below, according to the GRADE approach, which takes into account issues related to internal validity (overall risk of bias, inconsistency, imprecision, publication bias), and external validity (directness of results). Two review authors (TY, MM) will independently rate the certainty of the evidence for each outcome. We will resolve any differences in assessment by discussion or by consultation with a third review author (ZG).

We will present a summary of the evidence in a summary of findings table. This will provide key information about the best estimate of the magnitude of effect, in relative terms and as absolute differences, for each relevant comparison of alternative management strategies; the numbers of participants and studies addressing each important outcome; and a rating of overall confidence in effect estimates for each outcome. We will create the summary of findings tables using the methods described in the Cochrane Handbook, along with RevMan Web and GRADEpro software (GRADEpro GDT; RevMan Web 2023; Schünemann 2022).

If meta‐analysis is not possible, we will present the results in a narrative format in the summary of findings table. We will justify all decisions to downgrade the certainty of the evidence by using informative footnotes, and we will use GRADE guidelines for informative statements (Santesso 2016; Santesso 2020).

We will create summary of findings tables for the following comparisons and outcomes.

• Comparators:

  • No treatment or waiting‐list control

  • Usual care

  • Behavioural techniques only

• Outcomes:

  • Changes in body weight, BMI, or both

  • Quality of life score

  • Adverse events

  • Participant satisfaction

  • Diabetes status

  • Changes in depressive symptoms

  • Self‐confidence and self‐esteem

Notes

We have based parts of the Methods, as well as Appendix 1 of this Cochrane protocol, on a standard template established by the CMED group.

Appendices

Appendix 1. Search strategies

Cochrane Central Register of Controlled Trials (CENTRAL Ovid SP)

Part I: Intervention 1. exp Behavior Therapy/ 2. exp Counseling/ 3. exp problem solving/ 4. Family therapy/ 5. cognitive behavio*.mp. 6. (CBT or CB or CBGT* or bCBT or b‐CBT or MBCT*).mp. 7. ((multi systemic or multisystemic) adj2 therap*).mp. 8. family therap*.mp. 9. (dysfunctional adj2 (thought* or assumption* or rule* or appraisal* or belief* or attitude* or scheme*)).mp. 10 ((cogniti* or behavio*) adj3 (counsel* or intervention or therap* or psychotherap* or training or treatment or technique* or restructur* or defusion)).ti,ab,kf. 11 (rational emoti* or (problem* adj2 (focus* or sol*)) or psychoeducat* or role play* or schema* or self‐control* or self control*).ti,ab,kf. 12 (((psychotherap* or therap*) adj3 (commitment or acceptance)) or ((self* or stress*) adj3 (control or analysis or direct* or esteem or help or instruct* or manage*))).ti,ab,kf. 13 ((attribution* or reattribution*) adj3 (therap* or psychotherap*)).ti,ab,kf. 14 (mindfulness* or third wave or experiential or (behavio* adj3 (activation or modification)) or (thought* adj3 suppress*) or rumination).ti,ab,kf. 15. or/1‐14 Part II: Obesity/Overweight 16. exp Obesity/ 17. Overweight/ 18. Weight Loss/ 19. overweight.tw. 20. obes*.tw. 21. weight loss.tw. 22. ((reduc* or lose) adj5 weight).tw. 23. (body mass index adj5 (25 or 30)).tw. 24. or/16‐23 Part III: Part I AND II 25. 15 and 24

MEDLINE Ovid SP

Part I: Intervention 1. exp Behavior Therapy/ 2. exp Counseling/ 3. exp problem solving/ 4. Family therapy/ 5. cognitive behavio*.mp. 6. (CBT or CB or CBGT* or bCBT or b‐CBT or MBCT*).mp. 7. ((multi systemic or multisystemic) adj2 therap*).mp. 8. family therap*mp. 9. (dysfunctional adj2 (thought* or assumption* or rule* or appraisal* or belief* or attitude* or scheme*)).mp. 10 ((cogniti* or behavio*) adj3 (counsel* or intervention or therap* or psychotherap* or training or treatment or technique* or restructur* or defusion)).ti,ab,kf. 11 (rational emoti* or (problem* adj2 (focus* or sol*)) or psychoeducat* or role play* or schema* or self‐control* or self control*).ti,ab,kf. 12 (((psychotherap* or therap*) adj3 (commitment or acceptance)) or ((self* or stress*) adj3 (control or analysis or direct* or esteem or help or instruct* or manage*))).ti,ab,kf. 13 ((attribution* or reattribution*) adj3 (therap* or psychotherap*)).ti,ab,kf. 14 (mindfulness* or third wave or experiential or (behavio* adj3 (activation or modification)) or (thought* adj3 suppress*) or rumination).ti,ab,kf. 15. or/1‐14 Part II: Obesity/Overweight 16. exp Obesity/ 17. Overweight/ 18. Weight Loss/ 19. overweight.tw. 20. obes*.tw. 21. weight loss.tw. 22. ((reduc* or lose) adj5 weight).tw. 23. (body mass index adj5 (25 or 30)).tw. 24. or/16‐23 Part III: Part I AND II 25. 15 and 24 Part IV: Study filter [Cochrane Highly Sensitive Search Strategy for identifying randomized trials in MEDLINE: sensitivity‐ and precision‐maximizing version (2008 revision); Ovid format(Lefebvre 2022)] 26. randomized controlled trial.pt. 27. controlled clinical trial.pt. 28. randomized.ab. placebo.ab. 29. clinical trials as topic.sh. 30. randomly.ab. 31. trial.ti. 32. or/ 29‐34 33. exp animals/ not humans.sh. 34. 32 not 33 Part V: Study filter [Systematic Reviews Pre 2019 - MEDLINE] 35. (systematic review.ti. OR meta‐analysis.pt. OR meta‐analysis.ti. OR systematic literature review.ti. OR this systematic review.tw,kf,hw. OR pooling project.tw,kf,hw. OR (systematic review.ti,ab. AND review.pt.) OR meta synthesis.ti. OR meta‐analy*.ti. OR integrative review.tw,kf,hw. OR integrative research review.tw,kf,hw. OR rapid review.tw,kf,hw. OR umbrella review.tw,kf,hw. OR consensus development conference.pt. OR practice guideline.pt. OR drug class reviews.ti. OR (1469‐493X OR 1361‐6137).is. OR (1539‐8560 OR 1056‐8751).is. OR (2046‐4924 OR 1366‐5278).is. OR 1530‐440X.is. OR 2202‐4433.is.) 36. (clinical guideline.tw,kf,hw. AND management.tw,kf,hw.) OR ((evidence based.ti. OR exp evidence‐based medicine/ OR best practice*.ti. OR evidence synthesis.ti,ab.) AND (review.pt. OR exp diseases non mesh/ OR exp "behavior and behavior mechanisms"/ OR exp therapeutics/ OR evaluation studies.pt. OR validation studies.pt. OR guideline.pt. OR pmcbook.af.)) 37. (systematic.tw,kf,hw. OR systematically.tw,kf,hw. OR critical.ti,ab. OR (study selection.tw,kf,hw.) OR (predetermined.tw,kf,hw. OR inclusion.tw,kf,hw. AND criteri*.tw,kf,hw.) OR exclusion criteri*.tw,kf,hw. OR main outcome measures.tw,kf,hw. OR standard of care.tw,kf,hw. OR standards of care.tw,kf,hw.) 38. (survey.ti,ab. OR surveys.ti,ab. OR overview*.tw,kf,hw. OR review.ti,ab. OR reviews.ti,ab. OR search*.tw,kf,hw. OR handsearch.tw,kf,hw. OR analysis.ti. OR critique.ti,ab. OR appraisal.tw,kf,hw. OR (reduction.tw,kf,hw. AND (exp risk/ OR risk.tw,kf,hw.) AND ((exp "death"/ OR "death".af.) OR (exp "recurrence"/ OR "recurrence".af.)))) 39. (literature.ti,ab. OR articles.ti,ab. OR publications.ti,ab. OR publication.ti,ab. OR bibliography.ti,ab. OR bibliographies.ti,ab. OR published.ti,ab. OR pooled data.tw,kf,hw. OR unpublished.tw,kf,hw. OR citation.tw,kf,hw. OR citations.tw,kf,hw. OR database.ti,ab. OR internet.ti,ab. OR textbooks.ti,ab. OR references.tw,kf,hw. OR scales.tw,kf,hw. OR papers.tw,kf,hw. OR datasets.tw,kf,hw. OR trials.ti,ab. OR meta‐analy*.tw,kf,hw. OR (clinical.ti,ab. AND studies.ti,ab.) OR exp treatment outcome/ OR treatment outcome.tw,kf,hw. OR pmcbook.af.) 40. (letter.pt. OR newspaper article.pt.) 41. 35 or 36 42. 37 and 38 and 39 43. 41 or 42 44. 43 not 40 Part VI: Part IV AND Part V 45. 34 or 44 Part VII: Part III AND Part VI 46. 25 and 45

PsycINFO Ovid SP

Part I: Intervention 1. exp behavior modification/ or exp cognitive behavior therapy/ or exp cognitive techniques/ or schema therapy/ or behavior change/ 2. counseling/ 3. mindfulness‐based interventions/ or mindfulness/ 4. problem solving/ 5. cognitive behavio*.mp. 6. (CBT or CB or CBGT* or bCBT or b‐CBT or MBCT*).mp. 7. ((multi systemic or multisystemic) adj2 therap*).mp. 8. family therap*.mp. 9. (dysfunctional adj2 (thought* or assumption* or rule* or appraisal* or belief* or attitude* or scheme*)).mp. 10 ((cogniti* or behavio*) adj3 (counsel* or intervention or therap* or psychotherap* or training or treatment or technique* or restructur* or defusion)).ti,ab,kf. 11 (rational emoti* or (problem* adj2 (focus* or sol*)) or psychoeducat* or role play* or schema* or self‐control* or self control*).ti,ab,kf. 12 (((psychotherap* or therap*) adj3 (commitment or acceptance)) or ((self* or stress*) adj3 (control or analysis or direct* or esteem or help or instruct* or manage*))).ti,ab,kf. 13 ((attribution* or reattribution*) adj3 (therap* or psychotherap*)).ti,ab,kf. 14 (mindfulness* or third wave or experiential or (behavio* adj3 (activation or modification)) or (thought* adj3 suppress*) or rumination).ti,ab,kf. 15. or/1‐14 Part II: Obesity/Overweight 16. Obesity/ 17. Overweight/ 18. Weight Control/ 19. (adipos* or obes*).tw. 20. (overweight* or over weight*).tw. 21. (weight adj1 (reduc* or control* or manage* or maint* or loss)).tw. 22. or/16‐21 Part III: Part I AND II 25. 15 and 22 Part IV: Study filter ["PsycInfo Search Strategies" filter ‐ Best optimization of sensitivity & specificity version (Eady 2008)] 26. double‐blind.tw. or random: assigned.tw. or control.tw. Part V: Part III AND Part IV 38. 25 and 26

WHO ICTRP Search Portal (standard search)

obes* AND psycho* OR obes* AND cognitiv* OR obes* AND behavi* OR obes* AND counsel* OR obes* AND emotion* OR obes* AND mindfulness* OR obes* AND acceptance OR overweight* AND emotion* OR overweight* AND psycho* OR overweight* AND cognitiv* OR overweight* AND behavi* OR overweight* AND counsel* OR overweight* AND emotion* OR overweight* AND mindfulness* OR overweight* AND acceptance

ClinicalTrials.gov (advanced search)

Conditions: obesity OR obese OR adiposity OR adipose OR overweight OR "over weight" OR "weight reduction" OR "weight loss" OR "weight control" Interventions: psychotherapy OR "psycho therapy" OR psychotherapeutic OR psychotherapeutical OR psychological OR cognitive OR behavioral OR behavioural OR behavior OR behaviour OR counseling OR counselling OR acceptance OR commitment OR compassion OR emotion OR focussed OR focused OR "problem solving" OR psychodynamic OR schema OR stress OR validation OR mindfulness OR "third wave" OR "Family therapy" Age Group: Adult (18 to 65), Older Adult (65+)

Contributions of authors

All review authors read and approved the final review draft.

Cai Zhaolun (CZ): protocol draft, search strategy development, review of drafts, and future review updates
Tang Yiguo (TY): protocol draft and search strategy development
Mu Mingchun (MM): protocol draft, review of drafts, and future review updates
Zhao Guozhen (ZG): protocol draft and review of drafts
Luo Wenjun (LW): protocol draft and review of drafts
Li Bo (LB): protocol draft and review of drafts
Zhang Bo (ZB): protocol draft, review of drafts and future review updates

Sources of support

Internal sources

• Sichuan Univerisy, China

  Library Resources

External sources

• NA, Other

Declarations of interest

CZ: none known
TY: none known
MM: none known
ZG: none known
LW: none known
LB: none known
ZB: none known

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