Effectiveness of a Ketogenic Diet in the Treatment of Type 2 Diabetes Mellitus

5307 words (21 pages) Essay in Nutrition

23/09/19 Nutrition Reference this

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Health and Social Care Research: Methods and Methodology




Research Proposal


Word Count: 3009


  1. Title

Effectiveness of a ketogenic diet in the treatment of type 2 diabetes mellitus: a systematic review

  1. Background

Type 2 diabetes (T2DM) is a metabolic disorder characterized by continual hyperglycaemia and eventually causing a failure of insulin secretion by the pancreas (Packer and Castro, 2015). Diabetes affects around 382 million people worldwide (Diabetes UK, 2014). T2DM is strongly linked to obesity and physical activity (Packer and Castro, 2015). Patients with T2DM are at risk of complications such as renal impairment, retinopathy and peripheral never damage. They are also at high risk complications of stroke and cardiovascular diseases (Fowler, 2018).

KD is defined by elevated circulating ketone bodies, achieving a state of ketosis. This state is achieved by restricting carbohydrate to <50g per day and the predominant of calories coming from fats of 85% (Aragon et al., 2017). A study by Phinney et al. (1983) strongly emphasizes a diet low in protein is needed so that the reduction in carbohydrate calories are entirely compensated by fat. This puts the patient in a complete ketogenic state thus reducing blood glucose levels. A study conducted by Gumbiner et al. (1996) shows greater levels of circulating ketones when having a lower carbohydrate diet (24g) compared to higher carbohydrate diet which is very favourable in glycaemic control in diabetics. Haemoglobin A1C (HbA1c) provides a reliable measure of chronic hyperglycaemia and a good predictor of high risk complications (Sherwani et al., 2016). The diagnosis of T2DM is set by a cut-off point of 48 mmol/mol or more (6.5%) recommended by the expert advisory group (Farmer, 2012).

A number of studies have shown positive effects of KD on T2DM patients in reducing HbA1C levels (Boden et al., 2005; Scherger, 2017; McKenzie et al., 2017; Saslow et al., 2017; Hussain et al., 2012). Metformin, a popular and leading medication for the treatment of T2DM has similar effects of reducing HbA1c compared with the KD (Rojas and Gomes, 2013; Berstein, 2010). However, pharmacological interventions are often accompanied by reduced quality of life, economic burden and side effects (García-Pérez et al., 2013). This implies the need for alternative interventions without these negative effects. In the short term, rigorous lifestyle interventions tend to improve health outcomes for people living with diabetes. In a longer study participants following the KD did not present with any major side effects, in addition to better glycaemic control it also aided in significant improvements in both weight loss and metabolic parameters (Dashti et al., 2006). However more long-term studies are necessary to determine the possible adverse effects and the long-term acceptability of the diet.

Hypoglycaemia is the major side effect of diabetes medications in the treatment of T2DM. Hypoglycaemia can present with severe complications such as seizure, coma and even death. Prevalence of hypoglycaemia patients have increased due to more focus on tighter glucose control (Kalra et al., 2013).  A cross-sectional study of patients with T2DM treated with metformin and sulfonylurea found that patients had poorer medication adherence upon reporting a previous hypoglycaemic in fear of getting complications again. Non-adherence to medication can results in serious in health issues, with acute and chronic complications, more hospitalization and higher costs to healthcare (Lee et al., 2005). Moreover, different avenues of disease management would need to be considered because of increased T2DM prevalence and high costs of medication (Sokol et al., 2005).The removal of diabetes medications combined with clinically significant weight loss has been shown to generate health care cost savings (Cawley et al., 2014) .

In studies it was revealed that KD has improved glycaemic control in patients with T2DM such that medications were discontinued or even eliminated in participants (Westman et al., 2008; William et al. 2005; Boden et al., 2005; Nielsen and Joensson, 2008). This is evident that the KD is optimal in treating T2DM. Taking diabetes medications can inhibit ketosis and increase weight which is aimed for in the earliest phases of KD, therefore, reducing the effectiveness of being on the KD. However, it is evident through studies that being on the KD can override effects of diabetes medications enough for patients to come off them. Furthermore, patients following the KD should be under close medical supervision when adjusting dosages to prevent hypoglycaemia (William et al. 2005).

Obesity is a high risk factor in causing T2DM and can cause further cardio metabolic complications which are major causes of morbidity and mortality in T2DM (William et al. 2004). However, patients instructed to limit their carbohydrate intake to low levels have decreased levels of caloric intake. This overall reduced caloric intake may reduce their weight loss due to increased satiety (Johnstone et al., 2008). In previous research with non-diabetic patients have shown a positive correlation between level of ketonuria and weight loss success (Westman et al., 2002).  However, studies have shown that elevated ketosis improves glycaemia in T2DM patient’s independent of weight loss (Gumbiner et al. 1996; Westman et al. 2008).

In a study conducted by OK et al., (2018) it was found that patients had a greater compliance to the KD than a generalized diet. In order to stay compliant patients can inspect for ketosis by daily testing of their urine (Urbain and Bertz, 2016).   However, the induction of ketosis is influenced by the participant’s motivation to eat the meals found by Schmidt et al. using a single- arm pilot study. For participants to sustain motivation medical professionals should have an individualized approach to each patient maximising the effects of KD. Factors would be need to be considered such as age and socioeconomic status and having a shorter duration of follow ups (William et al. 2005).

Ketogenic diet being a favourable intervention compared to standard interventions makes the basis of this systematic review. It would be valuable to collate this firm evidence to support the need to bring in this intervention as there is limited research on this field. There are no reviews specifically on KD for the treatment of T2DM. The aim is addressed below:

The aim of this study is to evaluate the evidence to see whether the ketogenic diet can reduce HbA1c to the point that it can treat T2DM.

With the in-depth reading and evidence, I have moulded a question for this systematic review;

How effective is the ketogenic diet in reducing Hba1c compared to pharmacological interventions?












  1. Methods

There is evidence of primary research and basic literature when conducting searches on Google scholar around the topic in question. Extraction and synthesise of data will allow a critical analysis of the studies. This methodological section will discuss a rigorous search design extracting and synthesising the most relevant studies that will be transparent and reproducible.  https://ebn.bmj.com/content/ebnurs/14/3/64.full.pdf


Type 2 Diabetes Mellitus


Ketogenic diet


Standard intervention


Improvement in HbA1c

3.1   Search strategy

Evidence based medicine (EBM) often uses a specialized framework called PICO which stands for Patient, Intervention, Comparison and Outcome. This framework is outline by the Cochrane Collaboration (Higgins and Green 2011). Using search terms from table 1 using PICO framework enables an effective search strategy (Snowball et al, 1997). In table 2, there are compilation of a list of words that were identified that authors have used in their studies which includes synonyms, acronyms and rephrasing of key words. This increases the scope of studies for my inclusion and exclusion criteria which will be discussed below.

Table 1. PICO framework

Type 2 Diabetes Mellitus

Ketogenic diet

Standard intervention

Improved HbA1c


‘low-carbohydrate ketogenic diet’

‘Standard care’

‘Haemoglobin A1c’

‘Diabetes mellitus’

‘very low-carbohydrate ketogenic diet’

‘Routine care’


‘Non-insulin dependent- diabetes mellitus’


‘Routine intervention’

‘Blood sugar’

‘Type 2 Diabetes’

‘nutritional ketosis’

‘Usual intervention’

‘Standard intervention’

‘Usual care’

Table 2. Key words derived from searches using elements of PICO framework (table 1)

Conducting a systematic review, I can use a variety of relevant databases (table 4) to get as many papers as possible using elements of the PICO framework using the Boolean operators. Of the studies identified in the search I will check for reference lists and citation search for relevant and included studies. I will use a reference management software namely Mendeley to save the search results in an organized manner and get rid of duplicate studies.




‘T2DM’ OR ‘Type 2 Diabetes Mellitus’ OR ‘Diabetes Mellitus’ OR ‘Type 2 Diabetes’


‘Very low carbohydrate’ OR ‘low carbohydrate’ OR ‘Dietary carbohydrate restriction’


‘Standard intervention’ OR ‘Usual intervention’ OR ‘routine intervention ‘OR ‘usual care routine’ OR ‘                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    standard care’


‘Haemoglobin A1c’ OR ‘HbA1c’ OR ‘blood sugar’


S1 + S2 + S3 + S4

Table 3. Boolean operators; each search is assigned an identifier i.e S1



Allied and complementary medicine (AMED)

Covers relevant references to articles from over 600 journals, it covers professions allied to medicine, complementary medicine and palliative care. This study will aim to look at complementary medicine in the aim to treat the patient.

Cumulative Index to nursing and allied health (CINAHL) Plus

This tool covers nursing and allied health professional journals.


this study is looking at treating T2DM so will be helpful to look at clinical care and behavioural science journals in patients


This study would be helped by looking at psychology of patients following the KD


This has a large number of citations relating from MEDLINE and life science journals.

Cochrane Library

This tool consists of a collection of databases including: Database of Systematic reviews and central register of controlled trials.

Table 4. Databases will be used for using elements by using the Boolean operators.

3.2 Eligibility criteria

Text word searches will be performed using the searches from table 3 combining the terms in the set using operator ‘OR’ and combining sets using  operator ‘AND’.  This will focus a search down to as many relevant articles as possible. This first screening method will be on the title and abstracts exclusively. If answered No to any of the 3 eligibility criteria than they will not be reviewed for full screening as seen on Figure 2. The studies that have answered ‘Yes’ to all questions will be tabulated under the heading ‘passed’. Upon retrieval of full manuscripts they will be analysed against the inclusion and exclusion criteria. This will be completed by myself and a supervisor. We will have an in-detail discussion about our selection and settle any discrepancies. We will assess agreement using the agreement percentage;

AgreementsAgreements+Disagreements x 100

We will have an inter- rater agreement percentage of 80% which is considered to reflect good agreement (Mokkink et al., 2010).

Is the article


Making reference to Ketogenic diet

Is this primary research

Making reference to T2DM





Figure 2. Preliminary screening questions for first screening of research papers (see figure 3 for first screening) from titles and abstracts.



Study design

Randomised controlled trials, cohort studies

Any other studies that do not include randomised controlled trials and cohort studies.

Disease/ population


T1DM and any other disease and non-human studies


HbA1c outcomes

Non  HbA1c outcomes


English publications

Non-English publications

Table 4. Inclusion and exclusion criteria will be used on full text screening (see figure 2).

The inclusion of HbA1c as a primary outcome measure is used as a basis of easy comparison between data because it is a well-established measure of glycaemic control. No specific time frame, age of participants in trials and geographical scope was specified for this research. In addition, I will look at other outcomes which will include weight changes, medication changes, and other additional lifestyle interventions such as exercise recommendations, smoking cessation and alcohol consumption.

Randomised controlled trials are part of the inclusion criteria because they provide a high degree of internal validity. The results obtained will be reliable if the trials are of high quality. A set of guidelines that researchers should adhere to if they wish to report a good-quality trial have been published as the consolidated standards for Reporting Trials (CONSORT). 

In the aim of finding the ‘effectiveness’ of the ketogenic diet a search for primary research for ketogenic interventions will be performed. The selection process will include two steps; the first step will include the screening process which will be based upon titles and abstracts and the second screening process will be based upon retrieval and analysis of full texts as seen on figure 2. These two steps will also include searching for relevant journals, reference lists, citation indexes and contacting authors if needed of original articles (Horsley, Dingwall and Sampson, 2011). An exhaustive sampling strategy increases the quality of literature gathering all available knowledge.

3.3 Limitations

The ketogenic diet and education intervention can improve knowledge for primary care settings, but limitations in the studies don’t show the relationship between knowledge and behaviour. Several psychosocial mediators are related to diabetes self- care behaviour, including locus of control, coping styles, health beliefs and self-efficacy. Primary research evidence will be reviewed looking at these mediators to see participants behaviour towards the protocol and if this affected the validity of the results. Further, if in doubt I will contact the authors for further clarification.







Search for primary-level studies
Create database

Save titles and abstracts using reference management software


Remove duplicates



First screening based on titles and abstracts (see figure 2)

Meets 1 or more inclusion criteria




n excluded=

Reasons for exclusion

n full texts retrieved =


n tentatively included =


Second screening based on full texts

Meets all of the inclusion criteria

Meets 1 or more inclusion criteria





Figure 2. Exhaustive research methods retrieving and synthesising a set number of papers (n=) using a systematic approach.


When conducting my searches, I will use the Boolean operators in order for articles to be retrieved based on the four components of the PICO framework. These articles are assessed using the PRISMA guidelines as seen on figure 2. However, utilizing this method I want to limit the risk of biases. They can alter the findings and change the answer to a literature question. Publication bias involves studies that that report certain positive effects that go against strong prevailing beliefs (Khan, 2011). I aim to screen all articles for registration for trials because this represents the solution of publication bias. In addition, I will utilise a critical appraisal tool to assess the risk of bias in the studies.

3.4 Critical appraisal

Critical appraisal is an important in the process of systematic reviews. A critical appraisal tool will assess the trustworthiness, relevance and results of published papers. It enables a comprehensive protocol for critically appraising a research paper. CASP (critical appraisal skills programme) has developed several checklists, this provides a set of 10 questions as a guide to appraising quality to my research (Brice, R; 1999). As a novice researcher, my choice in using the CASP tool is because it is user-friendly and allows a fast evaluation (Hannes, Lockwood and Pearson, 2010). My study is based around quantitative studies, RCTs and cohort studies hence I will use checklists to provide a methodological quality to the study. I will critique each individual study using the appropriate checklist or a combination of checklists for that study. This will help develop a more realistic need for a SR. All questions will be addressed in the checklists to be included as part of my review.

3.5 Data extraction

Extraction of data from chosen articles will include HbA1C results as the primary outcome to this research. This will allow a visual assessment between results and allow comparison to standard interventions. Study designs includes the randomized controlled trials, cohort and cross-sectional studies. This will increase heterogeneity to my study.

Data extraction will also include:

  • Time-span of intervention; Ketogenic diet
  • Specific diet composition
  • Study characteristics- year, objective, research method and setting
  • Participant characteristics- number of participants, age, weight and gender
  • Adherence management- self- report, food records, urinary ketones, follow-up periods

All extracted information will be tabulated.  The tabulation of evidence helps in assessing practicality and improves overall transparency. This will aid meaningful comparisons ultimately achieving the aims of the study (Suri, 2011). In order to form a fair and holistic analysis contacting authors would be necessary to retrieve missing or further details. All contact will be made by email to the authors and they will be given a maximum of 15 days for a response.

A meta-analysis is not possible because the inclusion of studies are in different settings and have different designs which is results in heterogeneity. In addition there is lack of knowledge around statistics and time limitations.

3.6   Ethics 

There is no ethical considerations that need to be considered because this is a systematic review as no primary research is being carried out. However I will assess the ethics of trials in the research papers and if in doubt I will contact the authors. I will assess the papers that have passed the full-text screening to see if it is registered and has been approved by the ethics committee. I have ensured that my research question has not already been answered after exploring existing studies and that the research has been acknowledged by appropriate referencing.

  1. Conclusion

The uncovering of the research can help health-settings advocate a self-tailored diabetes management program which can include nutrition education, behavioural support and peer support via an online community. This can help patients wean off pharmacological interventions and gradually incorporate the ketogenic diet in to their lifestyle to help manage and treat their T2DM. If the KD has found a strong-evidence base for the treatment of T2DM I will be looking to get it published in medical journals targeting patients and healthcare professionals alike.

Further to this I will organize meetings with healthcare professionals in areas where there is a high prevalence of T2DM patients as well as promoting KD in flyers/leaflets, so they can be viewed by patients in healthcare settings. In addition, I aim to deliver talks to healthcare students in universities instilling facts and awareness about low carbohydrate diets and their effectiveness on T2DM patients.

  1. References
  • https://search.proquest.com/openview/e27f052d096f3f878d3cb41884d351c7/1?cbl=136155&pq-origsite=gscholar

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