EVIDENCE BASED MEDICINE
U3202727
WRITTEN ASSIGNMENT
I. PICOS FRAMEWORK + SEARCH STRATEGY
Case 4. Harry, a 56 year old picture framer, has type 2 diabetes. This morning Harry watched the following on one
of his Facebook feeds. Harry trust Dr Micheal Mosley, a TV doctor/reporter. Harry wants to know there is truth
behind the Youtube video, and should he commence taking vitamin C daily.
PICOS Table1
Question
Type
Treatment
Patient Problem or
Population
Male, late 50’s, type 2
diabetic
Intervention or Exposure
Comparison or Control Example Outcome Measures
5:2 diet, rapid weight loss through
intermittent caloric restriction
No intermittent fasting or Suppression of type 2 diabetes
dietary changes.
Clear HbA1c test
Baseline diabetic indicators
PICOS question: “In type 2 diabetic patients, does intermittent severe caloric reduction compared to no dietary
regulation help reduce the prevalence of type 2 diabetic indicators.”
A search was conducted in MEDLINE, CINAHL, PubMed, Cochrane Library for original primary evidence
investigating therapeutic use of intermittent very low calorie dieting (VLCD) on type II diabetics. The search terms
included “intermittent fasting”, “5:2”, “VLCD”, “type 2 diabetes”, “diabetes mellitus type 2”, “caloric restriction”,
and/or “very-low-calorie-diet”. Additionally, references in primary research in systematic reviews were also
assessed for relevant studies. Only primary research studies, which included outcome measures of diabetic
indicators were included.
After screening through various studies, five trials using the intermittent use of very low caloric diets for patients
with type 2 diabetes were narrowed down. The two trials then selected as primary evidence were preferred as the
included statistical analysis of diabetic indicators, namely fasting plasma glucose (FPG), glycated haemoglobin
HbA1c, and serum insulin. Additionally they met the age parameters of my patient.
III. RECOMMENDATION
With consideration for the appraised and reviewed primary research studies, certain outcome measures were
identified that helped conclude an answer to the patients query. Statistical analysis of data obtained in primary trials
supported each other in that both results concluded that intermittent very low caloric diet had a moderate overall
improvement on type 2 diabetic indicators, fasting plasma glucose (FPG) remained consistent in spite of dietary
changes, while serum insulin and HbA1c showed significant improvement following 20 weeks and 1 year
respectively of intermittent VLCD (5:2 diet) 3,5. Primary evidence one assessed these changes in diabetic measures
to be independent of weight from dietary changes3. Thus we are able to identify from existing trials the indication
of benefits from VLCD specifically for type 2 diabetic patients3,5, however in context of the patient, the results
observed could not be considered a “cure” to type 2 diabetes mellitus as Dr Michael Mosley suggests as results in
research show only a moderate difference3,5. If the patient would like to attempt the program then there may be
some benefit3,5, however the patient should not expect to no longer require existing medication5. Finally, additional
research suggests 1000mg daily supplementation of Vitamin C showed a statistically significant decrease in FPG,
HbA1c, and serum insulin2, as such introducing this supplementation into the patients diet would be beneficial to
his diabetic condition.
II. CRITICAL APPRAISAL
Primary Evidence I: The effect of short periods of caloric restriction on weight loss and glycaemic control in
type 2 diabetes3
The first study, by authors Williams KV MD, Mullen ML, Kelley DE and Wing RR of the Department of
Medicine, University of Pittsburgh, investigates if intermittent very-low-calorie dieting (VLCD) improves
glycaemic control more than moderate caloric restriction alone3. Appraisal of this primary research will consider
bias, internal and external validity4.
Patient population (n=54) was recruited through newspaper advertisements based on inclusion and exclusion
criteria; type 2 diabetic, age 30-70 years, >20% above ideal body weight in accordance with literature, not
receiving insulin therapy and no history of liver disease, renal disease, or heart disease3. Narrow criteria
strengthened external validity in terms of replicating results and lowered sampling bias as subjects do not reflect
general population4. Research design involved block randomisation address sampling bias, subjects were blocked
using fasting plasma glucose (FPG) values (<7.8, 7.8-11.1, >11.1 mmol), then randomised by blocks into three
treatment conditions3. No concealed allocation is mentioned however, which may increase potential performance
and interview bias as researchers are aware of which treatment is given to which subject group4, this may weaken
internal validity. FPG, glycated haemoglobin HbA1c, and serum insulin were measured before, at 10 weeks, and 20
weeks, the results of which were then analysed3.
When compared to the second study, all outcome measures analysed were relevant to the question posed, and thus
of clinical significance regarding type 2 diabetes following statistical analysis3,5. ANOVA, independent t-test and
chi-square tests were used to analyse results and obtain p values3. After analysing the results it was observed that
VLCD groups lost more weight (kg) than the standard group over 20 weeks3. No difference was recorded in fasting
plasma glucose levels between the groups at 20 weeks3, however it was reported significantly more (p =0.04)
VLCD subjects attained normal HbA1c levels compared with the SBT group3.
Primary Evidence II: Year-long weight loss treatment for obese patients with type II diabetes: does
including an intermittent very-low-calorie diet improve outcome? 5
This study involved a year long program that examined very low calorie diets (VLCD) in the treatment of type 2
diabetes5. As in the first study3, the patient population (n=93) was recruited through newspaper advertising with
narrow inclusion criteria very similar to the first study; type 2 diabetics, age 30-70 years, >30% above ideal body
weight in accordance with literature, no health problems that would preclude use of a VLCD5. The study reports
that subjects were randomly assigned to two groups5, but details regarding randomization and allocation methods
are not provided, this weakens internal validity and increases potential for bias4 when compared to the block
randomization of the first study, it might also be argued that this weakens external validity as replicating the study
will not be accurate4. Baseline values for all subjects were taken prior to randomization and notably no control
group was assigned5 meaning increased potential for historical bias since data could be compared against preexisting literature and initial measurements4, the first study included a third control group for this reason3, both
internal and external validity would thus be weaker compared to the first study.
Outcome measures were recorded for weight, glycaemic control, blood pressure and lipids5, these measures were
insufficient to accurately answer the question posed. Blood glucose levels (mmol/L) were recorded to assess the
impact on type 2 diabetes with HbA1 assessed only after ending the diet and restarting medication5. The first study
demonstrated little change in FPG as it was recorded to have remained consistent between groups and exhibited no
statistically significant change3, similar results were obtained and calculated in this study for FPG too (P =0.38)5.
HbA1 and insulin values showed significant improvement in the type 2 diabetes of VLCD groups, and analysis of
results revealed changes in HbA1 from baseline to be highly statistical significant (p <0.001) 5 which despite
supporting results obtained from in the first study3,5 is not clinically significant since the values were recorded
under different independent variables, this confounder weakens the internal validity present4. The study concludes
that while intermittently using a VLCD improved measures for type 2 diabetes, it does not justify clinical use of
VLCD, and that further research is needed5.
REFERENCES
1
Turner, M. (2014). "Evidence-Based Practice in Health.” Retrieved from University of Canberra
website: https://canberra.libguides.com/evidence
2
Afkhami-Ardekani M, Shojaoddiny-Ardekani A. Effect of vitamin C on blood glucose, serum lipids & serum
insulin in type 2 diabetes patients. Indian Journal of medical research. 2007 Nov 1;126(5):471.
3
Williams KV, Mullen ML, Kelley DE, Wing RR. The effect of short periods of caloric restriction on weight loss
and glycemic control in type 2 diabetes. Diabetes care. 1998 Jan 1;21(1):2-8.
4
Greenhalgh TM, Bidewell J, Warland J, Lambros A, Crisp E. Understanding research methods for evidence-based
practice in health. John Wiley & Sons; 2020 Jan 21.
5
Wing RR, Blair E, Marcus M, Epstein LH, Harvey J. Year-long weight loss treatment for obese patients with type
II diabetes: does including an intermittent very-low-calorie diet improve outcome?. The American journal of
medicine. 1994 Oct 1;97(4):354-62.
BIBLIOGRAPHY