PR O T O C O L Open Access

Weight maintenance interventions for

people with type 2 diabetes mellitus: a

systematic review protocol

Sarah Sauchelli

, Julia Bradley, Jennifer Cox, Clare England and Rachel Perry

Abstract

Background: Weight loss maintenance is a challenge for people with type 2 diabetes mellitus (T2DM), which

attenuates the long-term benefits of weight loss for diabetes management. Medication, specific dietary

requirements and the psychosocial burden of T2DM signify that weight loss maintenance designed for obesity may

not suit people with T2DM. The primary objective of this review is to comprehensively evaluate existing weight

maintenance interventions for people with or at high risk of T2DM.

Methods: We registered a protocol for the systematic review and meta-analysis of randomised and non-

randomised weight maintenance interventions for T2DM. Studies included will have been carried out in adults with

clinical diagnosis of T2DM or pre-diabetes. All intervention types will be accepted (e.g. behavioural/lifestyle change

and pharmacological). The primary outcomes will be weight control, glycaemic control and adverse effects.

Secondary outcomes will include cardiovascular risk factors (e.g. total cholesterol, LDL-cholesterol, blood pr essure

control), psychological wellbeing (including health-related quality of life), change in glucose medication and waist

circumference. Multiple electronic databases will be searched such as MEDLINE, EMBASE, Web of Science,

PsychINFO and international registers (e.g. Cochrane Central Register of Controlled Trials, WHO ICTRP). OpenGrey

will be searched for grey literature. Two researchers will screen all citations and abstracts. This process will also be

conducted by an additional researcher using a semi-automated tool to reduce human error. Full-text articles will be

further examined by the researchers to select a final set for further analysis, and a narrative synthesis of the

evidence will be presented. Potential sources of heterogeneity will be assessed, and a meta-analysis will be

conducted if feasible. Risk of bias will be evaluated using the Cochrane risk of bias tool and the certainty of

evidence using the GRADE (grading of recommendations, assessment, development and evaluation) approach.

Discussion: This review will critically appraise existing weight maintenance interventions targeting T2DM. Findings

will inform future intervention development to support people with T2DM delay weight regain and prolong

successful diabetes management.

Systematic review registration: PROSPERO CRD42020168032

Keywords: Weight maintenance, Type 2 diabetes, Systematic review

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* Correspondence: sarah.sauc[email protected]

National Institute for Health Research Bristol Biomedical Research Centre,

University Hospitals of Bristol and Weston NHS Foundation Trust and

University of Bristol, Level 3, University Hospitals Bristol Education and

Research Centre, Upper Maudlin Street, Bristol BS2 8AE, UK

Sauchelli et al. Systematic Reviews (2020) 9:210

https://doi.org/10.1186/s13643-020-01467-7

Background

The International Diabetes Federation reports that in

2019 approximately 463 million adults between ages 20

and 79 were living with diabetes mellitus, with projec-

tions estimating a rise to 700 million by 2045 [1]. The

existence of multiple comorbidities and an augmented

risk of mortality have placed diabetes mellitus as a global

health and development challenge [1]. More than 90% of

people with diabetes mellitus have type 2 diabetes melli-

tus (T2DM). Although a genetic pred isposition results in

an increased susceptibility among some individuals, ex-

cess weight, due to poor diet and insu fficient physical

activity, is the key modifiable risk factor [2]. Hence, life-

style change to maintain a healthy weight is a fundamen-

tal component of existing prevention and management

strategies [3].

Extensive literature shows that lifestyle interventions,

particularly those focusing on diet control, enable weight

loss, ameliorate cardiometabolic health and HbA1c con-

trol [4–7]. More recently, it has been demonstrated that

a very low-calorie diet encouraging weight loss enables

some people with T2DM reach a remission-like state

[8]. However, the majority of people with T2DM strug-

gle to maintain the weight lost once weight loss inter-

ventions have ended [9]. At 12-month follow-up, the

intervention benefits for weight, HbA1c levels, lipids and

blood pressure are less clear [10]. There is also some evi-

dence that weight loss maintenance is short-lived in

people with T2DM compared to non-diabetic people

with obesity [11] or people at high risk [6].

The primary target for diabetes manageme nt is glu-

cose control [3] and commonly used pharmacological

treatments for glucose regulation facilitate weight gain

[3, 12]. Medication used to treat psychiatric comor-

bidities and diabetes-related medical complications

can have a similar side effect [13, 14]. The specific

dietary requirements and the psychosocial burden of

diabetes self-management can also influence adher-

ence to physical activity and dietary guide lines among

this clinical group [15]. Behavioural interventions

shown to be beneficial for weight loss maintenance in

obesity [16, 17] may therefore not be equally applic-

able to people who additionally have T2DM.

The prescription of weight maintenance programmes

is among the American Diabetes Association’s recom-

mendations for medical care in diabetes [18]. Further, 4-

year weight maintenance (< 5% change from baseline

measure), particularly when combined with glycaemic

control, has been found to result in a reduction in med-

ical costs, compared to a 14% increase when weight gain

occurs alongside an incremental increase in mean A1C

levels [19]. Given the importance of weight maintenance

for diabetes-related health outcomes and the economic

savings for the healthcare system, development and

implementation of weight maintenance interventions

that are effective for people with or at high risk of

T2DM is crucial. Comprehensive reviews on interven-

tion effectiveness are fundamental for evidence-based

decision-making in clinical practice [20]. Yet, interven-

tions focusing on weight maintenance for people with

T2DM are yet to be systematically summarised and

assessed for quality.

Aims

The systematic review described in this protocol aims to

thoroughly evaluate the effectiveness of existing weight

maintenance interventions that have targeted people

with or at high risk of T2DM. It will consider glucose

regulation and weight as primary outc omes, in order to

discern features of current interventions that may aid

patients adhere to treatment targets and to identify chal-

lenges to be addressed by novel interventions.

A second objective of this review is to further evaluate

the applicability of text-mining tools and machine learn-

ing to support clinical systematic reviews. As the rate of

publication rises across disciplines, evide nce synthesis is

becoming increasingly more time-consuming [21]. Auto-

mated tools/processe s may reduce workload for re-

searchers. However, the use of varied terminology to

define medical phenomena and clinical interventions

often requires complex decision-making that may be dif-

ficult to predict prior to screening. Therefore, the trad-

itional systematic review screening process will be

carried out in parallel to a protocol using automated ap-

proaches to identify where human judgement may be

needed when conducting systematic reviews of studies

evaluating clinical interventions.

Methods

The present study protocol is reported in accordance with

the reporting guidance provided in the Preferred Report-

ing Items for Systematic Reviews and Meta-Analyses Pro-

tocols (PRISMA-P) statement [22] (Additional file 1). This

protocol has been registered in the International Prospect-

ive Register of Systematic Reviews (PROSPERO) database

(registration ID: CRD42020168032).

Eligibility criteria

Both published and unpublished studies including a

weight maintenance intervention will be analysed. Stud-

ies will be included irrespective of the country where

they have been carried out, year of publication and the

language of the report. Studies may be both randomised

and non-randomised, and blinding is not required given

that it is not always possible in behav ioural interven-

tions. The use of the findings from this review to de-

velop a novel intervention and design a randomised

controlled trial justify the inclusion of non-randomised

Sauchelli et al. Systematic Reviews (2020) 9:210 Page 2 of 7

studies [23]. Studies meeting the following criteria will

be deemed eligible for analysis (PICO structure).

Population

Participants will be adults (age ≥ 18 years), with a clinical

diagnosis of T2DM or pre-diabetes according to the cri-

teria of the World Health Organisation [24] or equivalent

international standards [25]. When it is unclear whether a

diagnosis was conducted, the study authors will be con-

tacted to obtain the information. Further, studies where

participants display impaired fasting glucose or non-

diabetic hyperglycaemia will also be included. Participants

will additionally have had to achieve weight loss within 24

months prior to the start of the weight maintenance inter-

vention or have been instructed to maintain their weight

as a preventative measure. No restriction will be placed on

the amount of weight loss achieved during a weight loss

programme given differential targets and success rates

across studies [26]. Participants may have been recruited

from the general community, hospital, clinical care centre

or other health services. Exclusion criteria include individ-

uals with overweight or obesity who do not have a diagno-

sis of pre-diabetes or T2DM, individuals with type 1

diabetes mellitus and individuals with conditions requiring

antipsychotic drugs.

Intervention

Behaviour change and lifestyle interventions (e.g. with a

focus on promoting physical activity and healthier eating

habits) will be included, along with pharmacological

treatments (e.g. lipase inhibitors such as orlistat) and nu-

trition therapies targ eting the modification of nutrient or

whole-food intake (as defined by the American Diabetes

Association [27];). Pharmacological treatments must be

approved as a weight loss drug by a regu latory agency

(e.g. European Medicines Agency or UK Medical Medi-

cines & Healthcare products Regulatory Agency), and

food supplements to complement the normal diet must

adhere to the definition provided by the Food and Drug

Administration on food supplements (see: https://www.

fda.gov/food/information-consumers-using-dietary-sup-

plements/questions-and-answers-dietary-supplements).

Both stand-alone and combined interventions will be in-

cluded, and any delivery approach for the non-

pharmacological interventions will be accepted (e.g.

face-to-face, online, as part of an education programme).

Papers will be excluded if the intervention focuses solely

on weight loss or the weight loss component is not

clearly distinguished from the weight maintenance

phase. Further, studies that use Ephedra as a supplement

will be excluded as it is banned in both the European

Union and by the Food and Drug Administration, as

well as those using Chinese traditional medic ine or

Ayurvedic medicine where there are no details of active

ingredients/herbs utilised.

Control/comparator

Single-cohort studies will be accepted, as well as studies

where the comparator is no intervention, standard or

minimal care, waitlist or the use of a placebo. When the

details of the information are unclear, authors will be

contacted to provide further information.

Outcomes

Primary outcomes will be those most important to pa-

tients receiving the interventions. These are weight

maintenance, glycaemic control (as indicated by one or

more of the following: HbA1c, fasting plasma glucose,

insulin sensitivity/resistance) and adverse effects. As

there is no current consensus on a definition for weight

maintenance, we will focus on weight difference between

baseline and at least one post-intervention measurement.

Adverse effects will be the physical and/or psychological

side effects that may emerge from the intervention (e.g.

disordered eating behaviour).

Secondary outcomes will include cardiovascular risk

factors (e.g. total cholesterol, low-density lipoprotein

cholesterol, high-density lipoprotein cholesterol, triacyl-

glycerol, diastolic blood pressure, systolic blood pres-

sure), psychological wellbeing (including health-related

quality of life), change to glucose medication and waist

circumference. Quantitative (both continuous and cat-

egorical) outcomes will be considered.

Should amendments be necessary, these shall be docu-

mented, reported and fully justified.

Information sources and search strategy

A systematic search of research conducted up to the

date of search initiation will be carried out. This includes

searching the following databases (no restriction on pub-

lication status):

1. MEDLINE and PreMEDLINE (OvidSP) (1950 to

date)

2. EMBASE Classic + EMBASE (OvidSP) (1974 to

date)

3. PsycINFO (OvidSP) (1806 to date)

4. CENTRAL (The Cochrane Library)

5. ISI Web of Science: Science Citation Index

Expanded (SCIEXPANDED) (1900 to date)

6. ISI Web of Science: Conference Proceedings

Citation Index-Science (1990 to date)

7. International trial registers (World Health

Organisation International Clinical Trials Registry

portal and ClinicalStudyResults.org)

Sauchelli et al. Systematic Reviews (2020) 9:210 Page 3 of 7

We will additionally conduct hand searches of refer-

ence lists and relevant systematic reviews, and we will

review the grey literature (e.g. conference papers/confer-

ence proceedings, theses, dissertations, studies published

in non-indexed journals) via OpenGrey. Personal letters

and e-mails will be sent to the corresponding authors of

papers in the field of weight management in T2DM. The

authors will be asked for information regarding unpub-

lished or ongoing studies.

Search terms identified for each of the following relevant

categories: population (“type 2 diabetes” or “diabetes melli-

tus” or “diabet es mell itus type 2” or “pre-diabetes” or “pr edi-

abetes” or “hyperglycaemia”), intervention (“weight

maintenance” or “maintained weight” or “weight mainte-

nence” AND “behav*” or “lifestyl e*” or “online” or “com-

puter” or “web” or “pharma*” or “food repla*” or “*supple*”),

and outcome (“weight” or “body mass index” or “BMI” or

“glycaemic* control” or “cardiovascular*

” or “psych*”). Bool-

ean searches will be carried out with terms combining cat-

egories and variations of the terms (via truncation). Medical

Subject Headings (MeSH) keywords and Emtree keywords

will be used. The draft search strategy for MEDLINE is pre-

sented in an additional file (Additional file 2).

Screening and data extraction

The search will be managed using the Rayyan (http://

rayyan.qcri.org) software app [28]. Results will be

imported into Rayyan, which automatically detects du-

plicates. Duplicates will also be detected through the

manual data screening process. We will seek information

regarding the outlined PICOs.

Two reviewers will independently screen all titles and

abstracts identified by the search strategy based on the

inclusion criteria. Articles that appear to meet the inclu-

sion criteria will be extracted and reviewed in full by two

authors. Inconsistencies will be discussed, and if unre-

solved another member of the team will be brought in

to make the final decision. Studies deemed irrelevant will

be excluded, and reason will be provided. Authors of un-

published studies will be contacted.

Semi-automated screening

Search results will additionally be uploaded to

AbstrackR, a citation screening programme functioning

on an algorithmic framework that predicts the likelihood

citations are relevant for further inspection [29]. Screen-

ing will be initiated by two reviewers until the

programme indicates it is ready to make predictions. Ci-

tations extracted through this approach will be com-

pared and cross-checked against the output of the

manual screening and selection process. Precision, false-

negative rate, number of relevant citations missed and

researcher time saved will be examined to determine the

usefulness of AbstrackR.

Data extraction

Two revie wers will independently extract the data of the

included studies using a standardised data extraction

form shown in an additional file (Additional file 3). This

includes the following:

1. Publication details (authors, title, date of

publication, country of origin, funding source,

corresponding author conta ct details)

2. Study characteristics (setting, study design, number

of patients randomised to each group)

3. Participant characteristics (demographics, clinical

characteristics)

4. Intervention and comparator characteristics. These

will be prespecified for each type of intervention.

We will also extract information from all included

studies on the following factors: mode of delivery

(verbal, written, computer, phone app), place of

delivery, who delivered the intervention, duration of

the intervention, number of sessions and format

(individual or group).

5. Outcomes (as detailed in the previous section). We

will record the number of participants assessed for

each outcome, the mean values and standard

deviations (if available) or medians and interquartile

ranges for continuous data and any reported

summary statistics (e.g. effect estimates, CIs,

standard errors, ranges).

Inconsistencies in data extraction will be discussed

and recorded. If needed, a third author will be included

in the discussion to reach a final decision. When data is

missing or inadequately described, three attempts will be

made to request the information from the corresponding

author.

Data synthesis

A narrative synthesis of all included primary studies will

be conducted. We will prov ide information on patient

populations studied, the interventions evaluated, and any

comparators used; how the studies have described and

measured patient-important outco mes; and a brief sum-

mary of results in relation to weight maintenance, glu-

cose control and adverse effects from the intervention.

This will provide initial insight on study heterogeneity.

A more detailed quantitative summary of the data for

each study included will be reported in a separate table.

The table will show location where the study was con-

ducted, population demographics, interventions and

comparators, assessment time frame and outcomes (pri-

mary and secondary separate ly). An overall synthesis of

the data extracted will be provided in the form of forest

plots for each of the primary outcome variables. All re-

sults of both primary and secondary outcomes will be

Sauchelli et al. Systematic Reviews (2020) 9:210 Page 4 of 7

reported in a results table. Overall effect size on out-

come change between baseline and follow-up assess-

ments will be reported as weighed mean differences with

95% confidence intervals.

Meta-analyses will only be conducted if data from

three or more studies were available. We will attempt to

combine the results for studies that use similar interven-

tions and report similar outcomes. However, there is

likely to be heterogeneity in the types of participants, the

intervention and its delivery. We will therefore be using

random-effects meta-analysis models for our primary

analysis to pool data across trials, where study weighing

is based on in-study and between-study variances. How-

ever, fixed-effect meta-analysis models will also be ex-

plored. All meta-analyses will be carried out with the

Comprehensive Meta-Analysis software [30]. Clinical

heterogeneity between studies will be evaluated by iden-

tifying variability in participants, baseline data, interven-

tions and outcomes. The I

statistic will be calculated to

quantify and interpret statistical heterogeneity [31]. We

will apply the following thresholds for the interpretation

of the I

statistic: 0 to 40%, might not be important; 30

to 60%, may represent moderate heterogeneity; 50 to

90%, may represent substantial heterogeneity; and 75 to

100%, represents considerable heterogeneity [32].

Pooled risk ratios and 95% confidence intervals (CIs)

will be calculated for dichotomous outcomes. Pooled

mean differences and 95% CIs or standardised mean dif-

ferences and 95% CI will be calculated for continuous

outcomes when results are reported on the same scale

(or can be converted to the same scale), or if results are

reported on different scales, respectively. When available

data does not enable statistical pooling, results will be

reported in a narrative format.

Subgroup analyses

If there is enough data, subgroup analysis will be com-

pleted. We expect that some weight maintenance interven-

tions may have been attached to the end of a weight loss

programme, while others might be stand-alone. Factors that

contribute to weight regain is time lapse since weight loss

intervention [33]. Hence, effectiveness of weight mainten-

ance interventions may be differential if they were preceded

by a weight loss intervention or not. We will also compare

studies based on intervention type (e.g. diet vs combined

behavioural), intervention delivery format (e.g. face to face

vs online) and duration of intervention, given that these

characteristics have previously been linked to effectiveness

in weight loss interventions [34–36].

Missing data

If data is not available in the format required, we will

first contact study authors or we will back-calculate the

data if possible (e.g. standard deviation from standard

errors or 95% CIs, mean and standard deviation from

median and range, etc.). Reasons for missing data will be

recorded (e.g. drop-outs, losses to follow-up and

withdrawals).

Risk of bias in individual studies

The Cochrane Risk of Bias Version 2 tool [37] will be

used for randomised controlled trials, while the

ROBINS-I tool [38] for observational studies. Two inde-

pendent reviewers will assess risk of bias using the rele-

vant tool. The latest version of the Cochrane risk of bias

tool (v2 [37];) assesses each study on the following 5

domains:

 Domain 1: Risk of bias arising from the

randomisation process

 Domain 2: Risk of bias due to deviations from the

intended interventions

 Domain 3: Risk of bias due to missing outcome data

 Domain 4: Risk of bias in measurement of the

outcome

 Domain 5: Risk of bias in selection of the reported

result

Justification for decisions will be presented as supple-

mentary material.

Additional analyses

A sensitivity analysis will be conducted including only

studies classified as low risk of bias. Any studies that had

imputed results will be removed from the pooled ana-

lysis. Fixed effects meta-analyses will also be conducted.

Further, we expect to carry out at least one sensitivity

analysis to ensure robustness of conclusions from pooled

estimate against variation in the timing of outcome as-

sessment by eligible studies. Furth er sensitivity analyses

may be conducted if deemed necessary depending on

the studies identified from the search.

If over 10 studies are identified, a funnel plot will be

generated to assess further publication bias.

Confidence in cumulative evidence

The strength of the overall body of evidence for each

outcome will be assessed using the GRADE system [39]

(software: https:/ /gradepro.org/), after generating a sum-

mary of findings table. Grading will be carried out by

the team of reviewers. Grading will be based on risk of

bias of individual studies, inconsistency (based on vari-

ation in point estimates, confidence intervals overlap, p

value of heterogeneity, I

score, outcome of the sub-

group analysis), indirectness (based on differences in in-

terventions and patients, method of measurement of

patient-important outcomes and comparison of inter-

ventions), imprecision (based on Optimal Information

Sauchelli et al. Systematic Reviews (2020) 9:210 Page 5 of 7

Size, sample size, overlapping confidence intervals and

judgement on the importance of observed differences)

and publication bias (based on funding sources, size of

studies and the comprehensiveness of data search).

Discussion

Multiple weight loss interventions have been trialled

for people with T2DM, showing substantial benefits

for diabetes management [40]. Yet, weight rega in

shortly after the completion of a weight loss

programme is commo n in T2DM [11]. Cost-effective

interventions to prolong weight loss maintenance in

T2DM are urgently needed. This review will examine

the effectiveness of existing weight maintenance inter-

ventions for T2DM with t he scope to inform the de-

velopment of future interventions that are tailored to

the needs of this clinical population. By comparing

the step-by-step outputs of the systematic process

when conducted solely by researchers versus when

the review is supported by automated tools, we will

further ascertain the amount of t ime saved when

these tools are applied, as well a s identify where hu-

man input is required to achieve accuracy. We aim to

use the information to generate a standardised proto-

col that researchers can adhere to when employing

automated tools to conduct systematic reviews on

complex clinical interventions. A speedier critical ap-

praisal of the existing literature without compromis-

ing quality will accelerate the development process of

evidence-based interventions. However, a limitation of

using semi-automated tools to assist screening is that

these tools are highly reliant on there being enough

eligible studies for “training” the syste m. Hence,

though semi-automated tools are highly promising to

facilitate reviews with large datasets, they may be less

applicable with more systematic reviews targeting a

less explored field of research.

We also expect that this review may require

consultation with authors of candidate citations as it

is common for weight maintenance interventions t o

be incorporated as part of a larger weight l oss

programme [8]. Discussions with healthcare profes-

sionals and experts in the field suggest that we will

identify a limited number of studies, the interven-

tions evaluated are likely to vary and the assessment

of outcomes are likely to occur at distinct time

points in relation to the intervention (particularly at

follow-up). Further, behaviour change and lifestyle

interventionsnormallyaddressmultiplefactors(e.g.

psychological, behavioural and nutritional) to enable

weight maintenance. Characteristics associated with

intervention effectiveness will therefore be hard to

pinpoint and is likely to require in-depth analysis.

Additional limitations that we may find inclu de small

sample siz es or no justification for sample size, a

short f ollow-up in assessment and poor reporting of

or no explanation for attrition. Given the above, we

expect to find high h eterogeneity among the in-

cluded studies and the need for caution when inter-

preting the pooled results.

Amendments made to this protocol will be recorded

on PROSPERO and reported in the final review manu-

script in a table format.

Supplementary information

Supplementary information accompanies this paper at https://doi.org/10.

1186/s13643-020-01467-7.

Additional file 1. PRISMA-P 2015 Checklist. Table guiding reader to

guide the reader through the sections of the protocol depicting the

recommended items to be addressed by a systematic review.

Additional file 2. Draft Search Strategy. Document providing an

example of a search strategy to be used during the database search of

the systematic review.

Additional file 3. Data Extraction Form. Template to be used to extract

relevant data of all included studies.

Abbreviations

T2DM: Type 2 diabetes mellitus; PRISMA-P: Preferred Reporting Items for

Systematic Reviews and Meta-Analyses Protocols; PROSPERO: International

Prospective Register of Systematic Reviews; PICO: Population, intervention,

comparison and outcomes; CI: Confidence interval

Acknowledgements

We thank Dr Kazeem Olorisade (University of Bristol) for providing advice

regarding the use of semi-automated tools to assist screening during the

systematic review process. Preparation of this protocol was supported by the

NIHR Biomedical Research Centre at University Hospitals of Bristol and Wes-

ton NHS Foundation Trust and the University of Bristol. The views expressed

are those of the author(s) and not necessarily those of the NIHR or the De-

partment of Health and Social Care.

Authors’ contributions

The protocol was developed by all authors. SS is the guarantor of the review

and drafted the manuscript. JB, JC, CE, and RP provided edits for manuscript

improvement. The authors read and approved the final manuscript.

Funding

The review will form part of the research programme of the NIHR Biomedical

Research Centre at University Hospitals of Bristol and Weston NHS

Foundation Trust and the University of Bristol. No external funding will be

sought for completion. The NIHR was not involved in the development of

this protocol.

Availability of data and materials

Not applicable

Ethics approval and consent to participate

Not applicable

Consent for publication

Not applicable

Competing interests

The authors declare that they have no competing interests.

Sauchelli et al. Systematic Reviews (2020) 9:210 Page 6 of 7

Received: 3 May 2020 Accepted: 25 August 2020

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