The purpose of this scoping review is to gain an overview on meal replacements and its outcome in managing patients with T2DM. Scoping review is identical to systematic review but differs in purpose as scoping review aims to comprehensively map the evidences of a topic while systematic review seeks to summarize and analyze the most ideal topic on a specific question [19].
The methods of this scoping review will be based on Arksey and O’Malley’s seminal framework for scoping reviews [19]. The approach to searching, screening and reporting of scoping review as suggested by Levac, Colqohoun and O’ Brien will be modified and utilized [26]. We will also use PRISMA-P as a checklist for aspects applicable to preparation of a scoping review protocol [27]. A completed PRISMA-P checklist is attached to this protocol (Additional file 1). The guidelines recommended in PRISMA Extension for Scoping Reviews (PRISMA-ScR) checklist will be followed when reporting the scoping review [28].
There are six stages involved in scoping review framework which included (1) identifying the research question, (2) identifying relevant studies, (3) selection of studies to be included, (4) charting of information and data from the studies, (5) collating, summarising and reporting the results and (6) conducting consultation with stakeholders and experts in diabetes.
Stage 1: Identifying research questions
- What are the types, composition, dosage, delivery and duration of meal replacement plans available for managing T2DM patients?
- What are the outcomes of meal replacement on glycaemic control/HbA1C, weight reduction and other health status of T2DM patients?
- What are the side effects experienced by T2DM patients taking meal replacements?
Stage 2: Identifying relevant studies
Identification of studies relevant to this review will be achieved by searching studies published between January 2000 to August 2020. The following PICO (population, intervention, comparator and outcomes) as shown in Table 1 below is used to help us identify relevant evidence to be included in the study.
The search will be conducted through several electronic databases (ie. Pubmed, Scopus, Cochrane Reviews, Google Scholar, Ebscohost, Science Direct, Web of Science). The search for online databases will be filtered for humans’ and adults’ results. The results will be downloaded into EndNote and duplicate results will be removed [29]. All reference lists of included studies and other reviews that we came across during database searching will be screen through to identify any additional eligible relevant studies to be included in our review.
We will also search for grey literature (local non-indexed journals, websites and theses) regarding meal replacement in managing patients with type-2 diabetes mellitus published within the same period. We will conduct a search through the first 20 pages of Google Search Engine to search for any related websites, non-indexed journals, research reports or articles. Searches will also be done on grey literature databases (Open Grey, Grey Literature Report, EMBASE Conference Abstracts and Web of Science Conference Proceedings Citation Index) to identify relevant reports or conference proceedings. Relevant health and diabetes organization websites including World Health Organization, American Diabetes Association, International Diabetes Federation, Diabetes UK, Joslin Diabetes Center, Ministry of Health Malaysia Virtual Library and Malaysia National Diabetes Institute will also be searched for resources related to the review. Apart from manual searching in theses room of National University of Malaysia, library database and online local theses database will also be searched to identify dissertations/theses that are applicable to this review.
Two independent reviewers (LC and AF) will be performing the search in parallel using a comprehensive search strategy. Search terms from PICO, key words, subject headings and synonyms such as meal replacement, type-II diabetes mellitus, glycemic control, weight reduction and risks will be generated by the research team members in order to capture any potential resources from the databases. Table 2 outlines the initial keywords and search terms generated. Boolean operators (AND, OR, NOT) will be used to combine search terms within related keywords and is adapted to the syntax used by each database. If there are any search terms missing from the initial search terms, an additional search will be carried out using the updated search terms. Table 3 shows the search strings generated.
Table 1 Table of PICO
Population
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This review will focus on adults with type-2 diabetes mellitus. Studies reporting on adult T2DM patients aged more than 18 years old will be included. Intervention including mixed population age will be included only if the data can be separated. There will be no restriction on severity of T2DM of subjects in the study.
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Intervention
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Any intervention or program utilizing self-administered meal replacements will be considered. Meal replacement is defined as prepackaged food products, drinks or meals that are designed to replace one or more meals and provide a defined amount of energy [20].
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Comparator
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No comparator is required for this review.
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Outcome
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Any studies that report the outcome related to health status of the T2DM subject, including glycemic control, weight reduction or side effects.
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Table 2 List of keywords and synonyms generated as search terms
Meal Replacement
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Type-2 Diabetes Mellitus
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Glycaemic control
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Weight reduction
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Risks
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Food Substitute
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Diabetic
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HbA1c
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Weight Loss
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Side effect
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Alternative Serving
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Diabetes
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Random Blood Sugar
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Weight reduction
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Danger
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Diet Alternative
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Non-insulin dependent Diabetes Mellitus
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Glucose
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Decrease in body weight
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Hazardous
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Alternative Nutrition
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Diabetes Mellitus-onset
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Fasting blood sugar
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Body Weight Changes
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Adverse effect
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Diet Replacement
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Type-II Diabetes Mellitus
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2-Hour Post-Prandial Blood Glucose
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BMI reduction
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Bad
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Diet plan Exchange
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Glucose tolerance
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Fatness
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Negative effect
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Replacement Drink
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Adiposity
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Harmful
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Alternate nutrition
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Detrimental
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Oral nourishing supplement
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Antagonistic
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Medicinal food
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Unsafe
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Table 3 List of search strings
Search string 1:
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“Meal Replacement*” OR “Food Substitute*” OR “Alternative Serving*” OR “Diet Alternative*” OR “Alternative Nutrition” OR “Diet Replacement*” OR “Diet plan Exchange” OR “Replacement Drink*” OR “Alternate nutrition” OR “Oral nourishing supplement*” OR “Medicinal food” AND “Type-2 Diabetes Mellitus” OR Diabetic OR Diabetes OR “Non-insulin dependent Diabetes Mellitus” OR “Diabetes Mellitus-onset” OR “Type-II Diabetes Mellitus”
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Search string 2:
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“Meal Replacement*” OR “Food Substitute*” OR “Alternative Serving*” OR “Diet Alternative” OR “Alternative Nutrition” OR “Diet Replacement*” OR “Diet plan Exchange” OR “Replacement Drink*” OR “Alternate nutrition” OR “Oral nourishing supplement*” OR “Medicinal food” AND “Type-2 Diabetes Mellitus” OR Diabetic OR Diabetes OR “Non-insulin dependent Diabetes Mellitus” OR “Diabetes Mellitus-onset” OR “Type-II Diabetes Mellitus” AND “Glycaemic control” OR HbA1c OR “Random Blood Sugar” OR Glucose OR “Fasting blood sugar” OR “2-Hour Post-Prandial Blood Glucose” OR “Glucose tolerance”
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Search string 3:
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“Meal Replacement*” OR “Food Substitute*” OR “Alternative Serving*” OR “Diet Alternative” OR “Alternative Nutrition” OR “Diet Replacement*” OR “Diet plan Exchange” OR “Replacement Drink*” OR “Alternate nutrition” OR “Oral nourishing supplement*” OR “Medicinal food” AND “Type-2 Diabetes Mellitus” OR Diabetic OR Diabetes OR “Non-insulin dependent Diabetes Mellitus” OR “Diabetes Mellitus-onset” OR “Type-II Diabetes Mellitus” AND “Weight reduction” OR “Weight Loss” OR “Weight reduction” OR “Decrease in body weight” OR “Body Weight Change*”
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Search string 4:
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“Meal Replacement*” OR “Food Substitute*” OR “Alternative Serving*” OR “Diet Alternative” OR “Alternative Nutrition” OR “Diet Replacement*” OR “Diet plan Exchange” OR “Replacement Drink*” OR “Alternate nutrition” OR “Oral nourishing supplement*” OR “Medicinal food” AND “Type-2 Diabetes Mellitus” OR Diabetic OR Diabetes OR “Non-insulin dependent Diabetes Mellitus” OR “Diabetes Mellitus-onset” OR “Type-II Diabetes Mellitus” AND “Risk*” OR “Side effect” OR “Dangerous” OR “Hazardous” OR “Adverse effect*” OR “Bad” OR “Negative effect*” OR “Harmful” OR “Detrimental” OR “Antagonistic” OR “Unsafe”
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Stage 3: Selection of studies to be included
Inclusion criteria for the search will be studies ranging from January 2000 to August 2020 related to meal replacement with T2DM affected patients aged 18 and above (adult and elderly). These will include articles from primary studies, technical reports and review articles. Grey literatures (ie. Websites, local non-indexed journals and theses) will also be included. Studies from all countries will be considered but studies that are not available in English and Malay will be excluded. Studies will also be excluded if they include (1) type-1 diabetes mellitus patients, (2) pregnant women, (3) paediatric populations, (4) are not human studies and (5) meal replacements that are not self-administered. Complete inclusion and exclusion criteria are as described in Table 4.
Screening and selection of articles will be carried out in a three step process. In the first step, two researchers (LC and AF) will screen through all titles from the search results in databases and grey literatures using the search term generated from stage two previously. All articles involving meal replacements and T2DM patients will be considered.
In the second step, all researchers (LC, AF, SS, ZAM and NMT) will be working independently to screen through the selected titles and abstract obtained from step one for articles potentially related to the objectives. Researchers will meet up to compare the results and to resolve discrepancies. A diabetes professional will be consulted if the discrepancies cannot be resolved.
In the third step, similarly, all researchers (LC, AF, SS, ZAM and NMT) will be working independently to screen through the full article obtained from the second step. Efforts will be made to obtain the full papers through university library if full papers are not available online. The full articles will be studied through to ensure that they meet the objectives. Researchers will meet upon completion to compare results and resolve any discrepancies.
Articles which are irrelevant to the objectives will be excluded and results of relevant articles from the search will be managed by Endnote X7 programme and its extracted data will be recorded in Microsoft Excel. The entire process of reviewing will be guided by using the PRISMA-ScR (PRISMA Extension for Scoping Reviews) checklist.
Table 4 Inclusion/exclusion criteria for study selection
Inclusion Criteria
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Exclusion Criteria
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Studies ranging from January 2000 to Aug 2020 related to meal replacement with T2DM affected patients aged 18 and above (adult and elderly).
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Studies that are not available in English and Malay language
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Studies with type-1 diabetes mellitus patients
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Studies with pregnant women
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Studies which are not human studies
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Studies which meal replacements that are not self-administered
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Stage 4: Charting of information and data from the studies
A data charting table (Additional file 2) is developed by the research team members to confirm relevance of studies screened and to extract findings from the studies. Findings will be extracted and categorized into table of evidences as below:
- Author(s)
- Publication year
- Objectives or purposes of the study
- Participants Characteristics – Age, BMI
- Study Design
- Settings
- Meal Replacement type
- Dosage and Calorie
- Control Groups (if any)
- Duration
- Effect on HbA1c and glucose
- Effect on weight reduction
- Effect on other health status
- Side effects
Other additional findings which are not included in the category of charting table are listed under an extra column labelled as ‘notable findings’.
The main outcome of the data will be type and dosage of meal replacement and its effect on HbA1c, glucose and weight reduction. Additional outcome will be the side effects of the meal replacement.
The charting table will be discussed by all researchers in a meeting and pretested before implementation of 10 articles to ensure the table captures significant information correctly. Two researchers (LC and AF) will then work independently to extract and chart the data from articles that are screened previously. The other researchers (SS, ZAM, NMT) will check the extracted data for accuracy. Any disagreements will be discussed during group meetings.
Stage 5: Collating, summarizing and reporting of results
The literature will be mapped and arranged with the concepts mentioned previously. The results of the data extracted will be summarized and analysed. The general characteristics of included studies will be summarised. Descriptive statistics such as percentages or frequencies will be used to provide summary characteristics of the studies based on the type of meal replacement plan being used in the studies. The studies will be categorized based on their study design. Data will be presented using a table of findings based on the effects of the meal replacement on glycemic control parameters and weight reduction. Risks and side effects of meal replacement products on T2DM patients will also be discussed. Limitation and research gaps for the studies will also be discussed to provide better recommendations for future meal replacement studies.
Stage 6: Consultation with stakeholders
Consultation with stakeholders and experts are optional but recommended in a scoping review. The expert will be able to provide assistance on finding relevant articles and also give extra feedback on the results and data analysed. We will present our findings at local related conferences. Feedback from the audiences will be recorded and used to supplement our findings.
Patient and Public Involvement
As this scoping review only involves literature-based studies, there is no patient or public involvement.