Hello, this is Sam from Ref-n-write. In this blog, I will explain how to write a clinical trial research paper for a medical journal.  We will go through the basic components that make up a good clinical paper. The title of our research paper is “The Effects of Vitamin D Supplements on Obesity: A Randomized Clinical Trial Study” I must insist that this is not an actual research paper from an actual medical journal. This is just an example medical research paper we put together for the purpose of teaching the process of writing up clinical trials.

The Effects of Vitamin D Supplements on Obesity: A Randomized Clinical Trial Study

Research Paper Title

1. Introduction Paragraph

Let’s start with the introduction paragraph. This is where you tell your readers what your topic is and why it is important. It is a good idea to start your intro paragraph with a hook. A hook is a powerful opening statement designed to grab the reader’s attention. This can be a fact, a statistic or a question. Since our study is about obesity, let’s give an interesting statistic about obesity. After starting with a broad statement, the next step is to narrow down the topic. In the second statement, we are dropping a hint that our paper is concerned with vitamin D and obesity. With the next statement, we are establishing the importance of the topic. We are saying that many people are dying due to obesity, and vitamin D is causing a lot of health issues, so we must do something about it. Then in the final statement of the intro paragraph, we explain how conducting research in this field will benefit the community. In our case, doctors will be able to prescribe better treatment options for obese patients. That concludes the introduction paragraph of our research paper.

Obesity is a Worldwide disease; In 2020, more than 2 billion adults, 18 years and older, were overweight. There is a general consensus in the research community that there is a strong association between obesity and Vitamin D. This represents an important and timely topic because obesity is currently fifth greatest risk of mortality, and Vitamin D deficiency has been associated with variety of chronic diseases. Better understanding of this link will greatly aid medical practitioners in effective treatment and management of obese patients.

Introduction Paragraph

2. Literature Review

Let’s move on to the literature review. This is where you provide a comprehensive summary of previous research on this topic. Let’s start with a broad statement summarizing the research in the area. In the first statement, we are saying that many studies have confirmed some link between vitamin D and obesity. Now let’s move on to specific studies. In the second statement, we are reporting the results of a specific study that came out recently and talks about the link between vitamin D and obesity in western countries. Now let’s talk about some mixed evidence that casts some doubt on the current understanding of the topic. In the final statement, we are saying that some studies have shown that obesity causes vitamin D deficiency, whereas other studies have shown that it is in fact, vitamin D that causes obesity issues among people.

Several studies have reported an association between low vitamin D levels and obesity levels [1-3]. Recently John et al, reported high prevalence of Vitamin D deficiency in several western countries with high levels of obesity [1]. Some studies suggested that obesity increased the risk of vit D deficiency [15] whereas other studies have shown the opposite [3].

Literature Review

3. Research Gap and Research Statement

Now it is time to establish the research gap. The previous statements we made, nicely lead to this statement. We are saying that we lack clear evidence linking vitamin D to obesity. We are also saying that most of the existing studies were conducted on subjects with preexisting health conditions, so there is a research gap to be filled. Now you must define your research question and explain how it addresses the research gap you established in the literature review. We are saying here that the study’s main aim is to investigate the effect of vitamin D on weight loss among the healthy population. We are also defining a specific hypothesis that we will either prove or disprove towards the end of the paper.

Due to lack of clear evidence, the link between vitamin D and obesity remains unclear. Moreover, most studies were conducted on subjects with preexisting health conditions or of certain background. The aim of the study was to examine the effect of vitamin D supplementation on weight loss among healthy population. We hypothesized that vitamin D could enhance weight loss without side effects.

Research Gap and Statement

4. Materials and Methods

Let’s move on to materials and methods. The ‘materials and methods’ is one of the most important parts of your paper. This section should have enough detail so that another researcher can reproduce your experiments and results.

4.1. Study Design and Ethical Approval

Let’s start with study design. In clinical trial papers, you must explain the study design employed in your work. In our case, it was a randomized, double-blinded placebo trial. Then you can talk about the location and period in which the clinical trial was conducted. Then provide details about the ethical approval that was obtained for the study. Nowadays, registering your clinical trial on the website clinicaltrial.org is a requirement before you begin recruiting patients for your study. You must also include the registration number.  I must warn you that many journals will refuse to publish the results of your paper if the clinical trial is unregistered. Good clinical practice (GCP) is a set of internationally recognized quality standards that must be followed when conducting clinical trials involving people.  It is a good idea to provide information about who is responsible for monitoring this for your trial.

The study was a randomized double-blind placebo-controlled clinical trial study. The study was conducted between April 2015 and March 2017 at five different hospitals in the central United Kingdom. This study was approved by the National Health Service ethical committee and registered on www.clinicaltrial.org as NC 34532. The trial was conducted according to the guidelines of good clinical practice (GCP) and monitored by the GCP unit at the hospital.

Study Design, Ethical Approval & Good Clinical Practice

4.2. Participant Recruitment and Consent

It is very important to define the inclusion and exclusion criteria used for the study. The inclusion criteria define the characteristics that will make subjects eligible for the study. In our case, we only included non-smoking and nondiabetic subjects with BMI greater than 25. The exclusion criteria define the characteristics that make subjects ineligible for the study. In our case, we exclude subjects participating in weight loss programs and taking dietary supplements. Now let’s detail the characteristics of the cohort, such as sample size, age, gender etc. In our case, we recruited 50 subjects in the age range of 15-60.

Let’s provide some information about the recruitment procedure. In our case, there was a face-to-face interview to confirm eligibility. And also, the eligible participants were asked to fill in a questionnaire so that we could gather demographic information. Another important part of the recruitment process is to get informed consent from the participants. The participants should be given all the information about the trial, including the benefits and risks, so they can decide whether to participate in the trial or not.

Subjects were included if they met the following criteria: (1) BMI>25; (2) non-smoker; and (3) no history of diabetes. Subjects participating in weight loss programs were excluded from the study. A total of 50 subjects (25 male & 25 female) participated in the study at the age range of 15-60. The eligibility was evaluated by interview. They were asked to fill in a questionnaire to gather demographic information. An informed consent was obtained from all the participants.

Inclusion/Exclusion Criteria, Patient Recruitment & Consent

4.3. Outcomes and Follow up

Let us now explain how the participants were divided into groups. In our study, the participants were randomly split into intervention and control groups.  The intervention group was given vitamin D supplements, and the control group was given a placebo. Our study is double-blinded, which means neither the participants nor the researchers knew which group they belonged to. Let’s talk about the follow-up period. Choosing an appropriate follow-up period for your study is important because a shorter follow-up period leads to an underestimation of the effects being measured. On the other hand, a long follow-up period increases the risk of subjects dropping out of the study. In our case, we have chosen a follow-up period of 12 months, and the measurements were performed every 6 months.

Then we have to explain what parameters we are measuring on the participants during the course of the study. In our case, we measured BMI, waist circumference and blood pressure.  BMI is the primary outcome. It means it is the most important outcome, and we will analyze the changes in BMI values to either prove or disprove our hypothesis. The secondary outcomes, such as waist circumference and BP, are additional measurements that we perform to provide supporting evidence for the main finding.

Participants were randomly divided into intervention and control groups, and received vit D supplements and placebo, respectively. Patients were assessed at 0,  6 and 12 months for a follow-up period of 1 year. BMI (primary outcome), waist circumference (secondary outcome) and BP (secondary outcome) were measured by a trained personal at each visit.

Grouping, Outcome & Follow-up Period

4.4. Statistical Analysis

Let’s talk about the statistical analysis and tools used for the study. In our case, we are using an independent sample t-test for statistical analysis. The independent sample t-test compares the means of two groups, in our case, the vitamin D group and the placebo group. We also specify the definition of statistical significance; if the p-value is less than 0.05, then we will consider the difference to be statistically significant. We also give the format of the data presented in the paper. In our case, all the data will be represented in the format mean ± SE.  We also mention the name of the statistical package used for the analysis. In our case, We are using SPSS statistical software, and the version number is 10.0.

Analyses were performed with independent t-test and paired t-test. All data were shown as mean ± SE. In all analysis, P value <0.05 was considered statistically significant. The data were analyzed using SPSS 10.0 (http://www.spss.com) software.

Statistical Analysis

5. Results

Let’s move on to the results section. This is where you present the core findings of your study. You have to present your results in a logical sequence. Do not interpret the results here. Instead, save them for the discussion section later. Before jumping into results, you must first let the audience know if you did any preprocessing or data cleanup before the analysis. In our case, four participants had to be excluded from the study due to health issues. And two participants dropped out due to personal reasons. So it means we are dealing with a slightly smaller sample size than we initially set out. Try to present your data in figures and tables, and only elaborate on the most important results in the main text. In our case, we are presenting the characteristics of both groups in a table. And we are plotting the change in BMI over time as a graph and presenting it as a figure in the paper.

From 50 participants, four subjects were excluded due to health issues. Two participants withdrew from the study due to personal reasons. Table 1 illustrates the characteristics of two groups participated in the study. In Figure 1, the BMI values are plotted as a function of duration for both groups. The results show that vitamin D supplementation caused a significant decrease in BMI (p<0.001). There was no significant difference in BP (p=0.71) between vitamin D (121 ± 3.1) and placebo groups (123 ± 4.2).


Now let’s start with the main finding. In our case, we found a significant drop in BMI among the cohort taking vitamin D supplements. Since we use the word significant, we have to provide a p-value. Let’s move on to the next result. We are reporting that there is no significant difference in blood pressure between the two groups. We are also providing actual values in the text. We have already mentioned in the methods section that the data will be in the format mean ± SE.

6. Discussion

Let’s move on to the discussion. This is where you interpret your findings and compare your results with previously published work in this domain. This is the place to talk about limitations and the future direction of your work. It is a good idea to start with the main result. In our case, we found that vitamin D reduces BMI, which supports the main hypothesis. Let’s also mention how these findings fit into existing research in the domain. In our case, these findings are in line with the results of previous studies published on this topic. Now, let’s move on to a negative result. In our case, we observed a negative association between waist circumference and vitamin D. Now give your interpretation of this negative result. We think it is because of the shorter duration of the study. Let’s report an unexpected result. In our case, we found that the blood pressure was a bit on the higher side with the cohort taking vitamin D supplements. Let’s give our interpretation of the result. We believe it is because of limited data.

Vitamin D supplementation significantly reduced the BMI over a 1 year period supporting the main hypothesis. The results agree well with the findings of existing studies [7-8]. A negative association was observed between waist length and vitamin D supplementation. The findings are in contrast with the previous studies [9-10]. This outcome is likely due to the shorter duration of the study. It was quite surprising to find that there was a slight increase in BP among the vitamin D group. The result must be interpreted with caution due to limited data.

Interpretation of Results

Let’s talk about the implications of our research. This is where you describe the significance of your findings. You must explain how your findings will benefit society. You can also explain how your findings contribute to the existing body of knowledge and impact future research in the area. Then add one or two lines about the novelty of your research. Explain what is so unique about your research. In our case, this is the first study to be conducted on a healthy population. Let’s move on to limitations. Every study has limitations. If you hide your limitations, I can guarantee that reviewers will reject your paper. Be honest about the limitations and explain how future studies can rectify the shortcomings of your work. In our case, the major limitation is that our study uses a small number of participants. Let’s move on to the final statement of the paper. Finish your paper with one or two lines about the possible future direction of your research. In our case, we can conduct a much bigger study to reconfirm our findings in the future.

The results demonstrated in this work provides a new perspective on the link between vitamin D and obesity from a clinical treatment perspective. To the best of our knowledge, this is the largest study to date to be conducted on health population. One of the most important limitation of the study is the small sample size. Larger clinical trials are needed to confirm the findings. This should be considered in future studies.

Implications, Limitations and Future work

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