Systematic Review: Lifestyle Interventions for Type 2 Diabetes

This systematic review examines the effectiveness of lifestyle interventions, specifically diet and physical activity, in preventing Type 2 Diabetes (T2D) among adults. The review addresses the rising prevalence of T2D, a major noncommunicable disease linked to lifestyle factors. It outlines a comprehensive search strategy using databases like CINAHL, MEDLINE, and Academic Search Complete, employing relevant keywords and Boolean operators. The inclusion and exclusion criteria are detailed, focusing on studies from 2012-2017 involving adults at high risk of T2D. The review also assesses the quality of the identified studies based on internal and external validity, and potential biases. The search yielded 372 results, with 96 studies ultimately included after screening. The methodological aspects of the initial ten studies were assessed for bias using the Cochrane tool. The review aims to determine the impact of combined diet and physical activity interventions on glycemic control and T2D incidence, considering factors like age, sex, ethnicity, and trial design.

Effectiveness of Lifestyle Interventions in the Prevention of Type 2 Diabetes Among Adults: A
Systematic Review
Name
Institution

Effectiveness of Lifestyle Interventions in the Prevention of Type 2 Diabetes Among
Adults: A Systematic Review
Literature Review
- The rise of noncommunicable diseases in recent decades has stood out as a significant
public health problem for both developed and developing countries.
- This rise is primarily attributed to both an ageing population, and also the shift to
nutrition and dietary habits of the western world and the sedentary lifestyles.
- This shift, especially and dietary habits is influence by both development (socioeconomic
and technological), urbanisation and globalisation (Alouki, Delisle, Bermúdez-Tamayo,
& Johri, 2016).
- Diabetes stands out as one of the major noncommunicable disease attributable to
nutrition.
- Its worldwide prevalence increases rapidly and especially in the developing nations. As
per the most recent statistics, 400 million people worldwide, 29.1 million people in the
US, 3.8 million people in the UK, and 1.2 million people in Australia suffer from
diabetes, with 90% of which present with type II diabetes (T2D) (International Diabetes
Federation, 2016; CDC, 2016; Australian Institute of Health and Welfare (AIHW), 2018;
Public Health England, 2016).
- Type 2 diabetes is a lifestyle disease which can be prevented by lifestyle changes, in
terms of changes in dietary habits and also increased physical activity.
- A number of studies have reported success in the reduction of T2D prevalence through
the of lifestyle interventions (Gong, et al., 2011; Diabetes Prevention Program Outcomes
Study Research Group, 2013).

- Weight control is central to the prevention and management of T2D independent of the
dietary factor.
- Owing to the fact that obesity is a major risk factor for T2D, lifestyle interventions aimed
at weight management are central to its prevention.
- Except for some Asian countries (China and India in particular), minimal research has
been conducted so far on diabetes prevention programs in developing countries.
- A number of systematic reviews on this topic have been conducted so far, and they do not
all reach the conclusion that there is enough data to recommend the use of lifestyle
interventions as advocated for by diabetes prevention programmes currently. As such,
this systematic review aims at addressing some questions:
a. Among high risk groups, does combined diet and physical activity interventions have an
impact on glycaemic control and the incidence of T2D?
b. Does the patient’s age, sex or ethnicity affect their participation in combined diet and
physical interventions and the resulting incidence of T2D?
c. Does the nature of the trial (explanatory or pragmatic trial) influence the effect of
combined diet and physical activity interventions on the participants?
Aims of this review
The questions outlined above spell the aim of this systematic review, which simply put, aims at
synthesizing recent evidence from the past ten years on the effectiveness of lifestyle
interventions in the management of weight in glycaemic control and eventually on the incidence
of type II diabetes among adults.

Search Strategy
In order to identify all relevant studies on the effectiveness of lifestyle interventions in the
management of weight in glycaemic control and eventually on the incidence of type II diabetes, a
search will be conducted on the following electronic databases: CINAHL, MEDLINE, and
Academic Search Complete. The search terms shown table 1 below will be used. The alternative
keywords and phrases as identified using thesaurus, a search on Google Scholar followed by
scanning of the results for alternative words and phrases, and lastly, the use of the US National
Library of Medicine’s Medical Subject Headings (MeSH) search are shown in the third row and
will be used accordingly.
Patient or Population or
Problem
Intervention (or
Exposure)
Comparison Outcomes
Type II Diabetes  Diet
 Physical activity
N/A  Weight management
 Glycaemic control
 Incidence of type II
diabetes
 Diabetes Mellitus
 Noninsulin-
Dependent Diabetes
Mellitus
 Type 2 Diabetes
 Type 2 Diabetes
Mellitus
 Dietary
Management
 Nutritional
Management
 Diet Therapy
 Diet Habits
 Feeding
Behaviour
 Nutritional
Therapy
 Exercise
 Physical
Education and
Training
N/A  HBA1c
 blood sugar
 Weight reduction plan
 Diabetes mellitus
incidence
 Incidence of diabetes
mellitus
 Type II diabetes
incidence
 Incidence of Noninsulin-
Dependent Diabetes
Mellitus
The MeSH and other relevant terms as identified above will then be combined with Boolean
operators “AND” and “OR” and used appropriately. This will lead to combinations such as (i)

“Type II Diabetes (title)” OR “Diabetes Mellitus (MeSH)” OR “Noninsulin-Dependent Diabetes
Mellitus (MeSH)” OR “Type 2 Diabetes (MeSH)” OR “Type 2 Diabetes Mellitus (MeSH)”
AND (ii) “Diet (title)” OR “Dietary management (MeSH)” OR “Nutritional management
(MeSH)” OR “diet therapy (MeSH)” OR “diet habits (title)” OR “Feeding Behaviour (MeSH)”
OR “Nutritional therapy (MeSH)” OR “physical activity (title)” OR “exercise (MeSH)” OR
“Physical Education and Training (MeSH) AND (iii) “glyc##mic control (title)” OR “HBA1c”
or “blood sugar” OR “weight management (title)” OR “weight reduction plan (MeSH)” OR
“incidence of type II diabetes (title)” OR “diabetes mellitus incidence (MeSH)” OR “incidence
of diabetes mellitus (MeSH)” OR “type II diabetes incidence (MeSH)” OR “incidence of
Noninsulin-Dependent Diabetes Mellitus (MeSH)” OR “Maturity-Onset Diabetes Mellitus
(MeSH)”. Truncation and wildcards will be used sparingly, with the following terms “adult*”,
Diabet####”, “gly##mic”. The search will be limited to studies that involved adults as
participants.
Additional searching will also be done on the reference lists from the identified relevant
systematic reviews
The results from the search will be imported to Endnote X7 to be assesses of relevance to the
current review, duplicates and those not in English language will be removed. The remainder
will be assessed by title alone, and the irrelevant ones will be removed. The abstracts of the
remaining studies will then be assessed. The full texts of those that will remain will be examined
against the following inclusion and exclusion criteria:
i. Original research articles published in peer-reviewed journals.

ii. The study participants were adults (18 years and above), and classified to be at a high risk
of developing the disease attributable to aggregation of risk factors such as obesity,
impaired fasting glycaemia, gestational diabetes, or impaired glucose intolerance.
iii. The study will include the interventions of dietary modifications or physical activity or
both for the prevention of the condition or weight management and control of obesity.
iv. Studies whose outcomes are weight management, glycaemic control, incidence of type II
diabetes and other relevant outcomes.
v. Studies published between January 2012 and December 2017.
vi. Studies that were only published in English and not translated from any language.
vii. The article’s full text has to be accessible.
viii. Studies conducted both in the clinical and in an academic environment.
The following will be the exclusion criteria:
i. Duplicate copies of the same study
ii. Studies published in a language other than English
iii. Student thesis reports and studies published on company websites.
iv. Books or book chapters.
Those studies that will have met the above inclusion and exclusion criteria for the review will be
tabulated.
Study quality assessment
The quality of the identified documents will be then analysed. The quality will be based on three
factors: internal validity, external validity, and bias. Study quality assessment will be conducted
for the purposes of evaluating the validity of the identified studies. As reiterated by Staples and

Niazi, (2007), it is quite challenging to determine the extent to which threats of validity have
been addressed by the researchers. Therefore, the quality assessment has to be based on research
paper structure criteria. For the current study, the assessment will be evaluated on structure:
Introduction, Research Method, Results, Research Conduct and Ethical Concerns, and
Conclusion. The researcher will evaluate whether each potential study answers the following
questions.
i) Does the paper’s introduction section provide an overview of diabetes, and lifestyle
modifications?
ii) Does the study clearly describe the research methodology adopted?
iii) Are the study results defined in the paper? Are they helpful in answering the search
questions developed for the current study?
iv) With regard to research conduct and ethical conduct, does the researcher uphold the
research code of conduct in the region which the study was undertaken? Generally, the
paper should outline how the research upheld the principles of; (a) honesty in
communicating the research goals, methods and procedures, (b) reliability in performing
the research and also communicating the results, (c) objectivity in interpretation and
concluding on the facts and data arrived at, (d) impartiality and independence from
interested parties or economic or financial interests, (e) openness and accessibility of the
study and its materials, (f) duty of care for the study participants, (g) fairness in proper
referencing and giving due credit to the work of others, (h) responsibility for future
science generations (European Science Foundation:, 2017).
v) On the conclusion section, does the paper report the findings (both positive and negative
properly) And does it address the study’s limitations?

Search Results
A search on MEDLINE with Full Text, CINAHL, and Academic Search Complete identified 372
results. A total of 90 duplicates were removed. Upon assessment of the titles and abstracts of the
282 remaining studies, another 27 studies were excluded, leaving 255 full-text articles for further
review (figure 1 below). One (1) paper was further excluded as it had originally been published
in Spanish, and even though it was re-published in English, it was excluded as per the current
review’s inclusion and exclusion criteria. Out of the 254 remaining full-text articles, 158 were
excluded. One article was excluded on the basis of just being a study protocol for a study in the
future, 5 articles were excluded for not specifying the type of diabetes that was studied, another 8
studies had included subjects who had not made the cut-off age for the current study (18 years).
Further, another 11 studies were not accessible, 45 were not peer-reviewed, 37 did not adopt a
lifestyle-based intervention (diet or physical activity), another 26 did not meet this systematic
review’s criteria, and the abstracts of another 25 studies did not contain adequate information to
determine the inclusion criteria had been met.
The 96 remaining studies recruited adult samples of 30 to 7,467 participants. The reported mean
age was on average, 45 years (37 to 50 years). Female participants made up about 60%. the
studies had adopted either diet or physical activity as the lifestyle interventions, and they
measured the outcomes in terms of weight management, glycaemic control and incidence of type
II diabetes mellitus.

Screening
Included
Eligibility
Identification
Full-text articles assessed for
eligibility
(n= 254)
Full-text articles excluded (n= 158)
Reasons
study protocol only (n = 1)
Not specific on type of diabetes (n=
5)
Subjects aged less than 18 years (n=
8)
Unable to gain access to full text (n=
11)
Not peer reviewed (n= 45)
Not a lifestyle-based intervention (n=
(37) Intervention
Did not meet systematic review
criteria (n= 26)
Abstract with inadequate information
to determine the inclusion criteria was
met (n=25)
Studies included in review
(n = 96)
Records identified through
database searching (n= 372)
(n = )
Records after duplicates removed
(n = 282)
Records screened
(n = 282)
Records excluded on the basis of
titles and abstracts (n = 27)
Figure 1: Flow chart demonstrating handling or results returned by the search
Non- English language paper
excluded (n= 1)

Risk of bias within studies
The methodological aspect of the first ten included studies were assessed for risk of bias. The
assessment was carried out as per the Cochrane collaborations tool for assessing risk of bias
(Higgins, et al., 2011). As per the tool, the studies are assessed on 7 parts where there is the
likelihood of bias. On the 7 domains, one is to respond with either a ‘yes’ to indicate low risk,
‘no’ to indicate significant risk, or ‘unclear’ to indicate that there was not enough information to
come up with the decision on the risk of bias. The median score was 7 (minimum -1, maximum
9); only three studies (Frank et al., 2014; Jacobs et al., 2015; Liubaoerjijin, Terada, Fletcher, &
Boulé, 2016) were regarded as having a low risk of bias , five (Mandalazi, Drake, Wirfält, Orho-
Melander, & Sonestedt, 2016; Parajuli, Saleh, Thapa, & Ali, 2014; Sangeetha et al., 2013; Shu,
Chan, & Huang, 2017; Yom-Tov et al., 2017) had moderate risk , while two (Grøntved et al.,
2014; Mikus, Oberlin, Libla, Boyle, & Thyfault, 2012) were regarded as having high risk .

References
Alouki, K., Delisle, H., Bermúdez-Tamayo, C., & Johri, M. (2016). Lifestyle Interventions to
Prevent Type 2 Diabetes: A Systematic Review of Economic Evaluation Studies. J
Diabetes Res., 2159890.
Australian Institute of Health and Welfare (AIHW). (2018, January 18). Diabetes. Retrieved
from Australian Institute of Health and Welfare: https://www.aihw.gov.au/reports-
statistics/health-conditions-disability-deaths/diabetes/overview
CDC. (2016, July 25). Working to Reverse the US Epidemic: At A Glance 2016. Retrieved from
Centers for Disease Control and Prevention:
https://www.cdc.gov/chronicdisease/resources/publications/aag/diabetes.htm
Diabetes Prevention Program Outcomes Study Research Group. (2013). Long-term effects of the
Diabetes Prevention Program interventions on cardiovascular risk factors: a report from
the DPP Outcomes Study. Diabet Med, 46-55.
European Science Foundation: (2017). European Code of Conduct. Berlin: All European
Academies.
Frank, L. K., Kröger, J., Schulze, M. B., Bedu-Addo, G., Mockenhaupt, F. P., & Danquah, I.
(2014). Dietary patterns in urban Ghana and risk of type 2 diabetes. The British Journal
Of Nutrition, 112(1), 89-98. doi:10.1017/s000711451400052x

Gong, Q., Gregg, E., Wang, J., An, Y., Zhang, P., Yang, W., . . . Bennett, P. (2011). Long-term
effects of a randomised trial of a 6-year lifestyle intervention in impaired glucose
tolerance on diabetes-related microvascular complications: The China Da Qing Diabetes
Prevention Outcome Study. Diabetologia, 300-7.
Grøntved, A., Pan, A., Mekary, R. A., Stampfer, M., Willett, W. C., Manson, J. E., & Hu, F. B.
(2014). Muscle-strengthening and conditioning activities and risk of type 2 diabetes: a
prospective study in two cohorts of US women. Plos Medicine, 11(1), e1001587-
e1001587. doi:10.1371/journal.pmed.1001587
Higgins, J. P., D. G., Gøtzsche, P. C., Jüni, P., Moher, D., & Oxman, A. D. (2011). The
Cochrane Collaboration’s tool for assessing risk of bias in randomised trials. BMJ,
d5928.
International Diabetes Federation. (2016). Facts and Figures. Retrieved from International
Diabetes Federation: http://www.idf.org/WDD15-guide/facts-and-figures.html
Jacobs, S., Harmon, B. E., Boushey, C. J., Morimoto, Y., Wilkens, L. R., Le Marchand, L., . . .
Maskarinec, G. (2015). A priori-defined diet quality indexes and risk of type 2 diabetes:
the Multiethnic Cohort. Diabetologia, 58(1), 98-112. doi:10.1007/s00125-014-3404-8
Liubaoerjijin, Y., Terada, T., Fletcher, K., & Boulé, N. G. (2016). Effect of aerobic exercise
intensity on glycemic control in type 2 diabetes: a meta-analysis of head-to-head
randomized trials. Acta Diabetologica, 53(5), 769-781. doi:10.1007/s00592-016-0870-0
Mandalazi, E., Drake, I., Wirfält, E., Orho-Melander, M., & Sonestedt, E. (2016). A High Diet
Quality Based on Dietary Recommendations Is Not Associated with Lower Incidence of