Overview of the DIETFITS randomized clinical trial

In the research conducted by the authors of this paper, it is observed that the study is based to find out an alternative factor that can possibly contribute in weight loss (Gardner et al., 2018). Obesity have been one of the concerning health threat to a large group of population around the world. There have been many researches conducted upon tackling with this health issue and one of the most effective one is dietary modification. Within the category many research have been conducted in determining the significant factors that would be one of the contributing factors for weight loss. In this particular paper, the authors try to implement the effectiveness of healthy low-carb diet and healthy low fat diet that would accelerate the chances of weight loss. The comparison is drawn between healthy low-fat diet and healthy low-carbohydrate diet and the effectiveness of these two diets in bringing change in overweight individuals. Dietary modification is essential for the purpose of weight loss however; a specific dietary plan is not effective for every individual. In prior researches genotype structure and insulin secretion were considered to be the contributing factors in modification of dietary effectiveness (Milagro et al., 2013). However, in this particular paper authors try to examine the effectiveness of healthy low-fat diet and healthy low-carbohydrate diet in weight loss. The aim of this paper is to find out which diet is more effective in dietary modification for the purpose of dealing with overweight. In addition to this, the paper aims to find relation of insulin secretion or genotype sequence with the effectiveness of diet in accelerating weight loss. The primary hypothesis of this paper was that the genotype structural interaction could have a significant effect on weight loss. The second primary hypothesis was that the insulin secretion interaction have a significant effect on weight loss. The other hypothesis of the paper was that the healthy low-fat diet have positive result in achieving weight loss along with a healthy low-carbohydrate diet have an accelerating effect in contributing weight loss.

The Stanford University approved the methodology adopted for this particular study. A randomised controlled trial was conducted for this study where all the participants participated with their individual consent. A total number of 609 adults were taken for conducting this research. The recruitment procedure for the purpose of this particular study was based on the areas of Stanford and San Francisco, California. The participants consisted of male and premenopausal female subjects with the age range of 18 to 50 years old. However, the individuals suffering from diabetes, cancer and other health concerns were excluded from the research study since this might have affected with the weight change. The study was conducted for a period of 12 months. The participants were randomly put on a healthy low-fat diet or low-carb diet trials for 12 months. A number of factors were taken into consideration before the recruitment procedure of the candidates for this research. Men and women from the age group of 18 to 50 years old were selected as the subject for conducting trials of the dietary plan. Adults who were suffering from chronic diseases were avoided for the study as this might have hampered with the result of the study. In addition to this, a written consent was signed from every candidate in order to provide a legal confirmation for the research. Now for recruiting the participants for this specific study, advertisements along with email lists were prepared from previous recruited participants of nutritional studies. The randomisation procedure for implementing dietary plan of healthy low-fat and low-carb diet was performed with the help of allocation format of a computerised random generation of number. In addition to this, the main study design for this research paper was factorial design that consisted of two factors – genotype pattern matching and insulin secretion interaction.

Comparison of low-fat and low-carbohydrate diets for weight loss

The research conducted for this particular study did not support the hypothesis stated by the authors of this paper. The results that were discovered after the completion of the study did not show any major difference of weight change between the two distinctive groups that were formed for the purpose of study. No significant change in weight loss was observed among the participant who were on trial for healthy low-fat diet and healthy low-carb diet. Additionally, neither there was not any significant relation of weight loss with genotype pattern interaction and insulin secretion as well. Therefore, the hypothesis that was stated by the authors of this paper were not supported. The hypothesis that was constructed by the authors failed to support with the experiment that was conducted for this research project. However, one reconcilable outcome from this research was that a low-carb diet proved to be effective for those individuals who have higher insulin secretion levels or higher insulin resistance level. In either case, the low carb diet was found to be superior to low-fat diet. The weight loss that was observed between the two distinctive randomised groups of individuals was not significant and not necessarily meaningful clinically. The results show that in the group who were on trial for healthy low fat diet had a weight loss amount of -5.3 kilograms whereas for group who were on healthy low carbohydrate diet was -6.0 kilograms. The difference of weight loss between the two distinctive groups were not significant to prove the hypothesis of the study.

The 609 random participants for this particular research were the main subjects upon which the dietary trials were conducted. Initially 1057 individuals were screened for the eligibility of this study. However, after exclusions of participants due to certain criteria and eligibility, the number of participants were reduced to 609. Now, this reduction in number of participants were limited to a small group of individuals and the research design could not fully take place over an extensive group of people. The results may have been different if the number of participants would have been more in number (Zohrabi, 2013). Another potential threat to internal validity in the research design could be due to the prior occurrences that could affect the results of the research (Kratochwill, 2015). For this particular research design, the consideration of genotype pattern and insulin secretion interaction might have been a potential threat to the study, as it would significantly influence the weight of the individuals and as a result affecting upon the results on the study. The second potential threat to internal validity in a research design could have been maturation of the subjects who were chosen for the study (St. Clair, Cook & Hallberg, 2014). Hence, in this particular study there might have been a possibility that among the 609 chosen participants some may had certain health issues that would have caused a variation in the results or the number of participants for the study. One of the key threat that a research design could face internally is the mortality of the subjects chosen for the research (Fok, Henry & Allen, 2015). In this particular research, there might have been possibility of participants dropping out of the research as a result of lack of interest. In fact, 142 candidates dropped out of this particular study programme due to lack of interest towards the study. Some of the potential threats to external validity of a research design could be population related threats. For this particular study, the participants were chosen from San Francisco and Stanford only however, the objective of the study was for a large population.

Association of genotype pattern or insulin secretion with dietary modification effectiveness

Hence, from the above discussion it can be concluded that the research have faced some threats that may have influenced the outcomes of the research. Some of the recommendations that could have been helpful in avoiding these potential threats to validity of this research design. The duration of the research could have been shorter instead of 12 months long duration in this way, the prior studies related to this subject could have been minimised in terms of a threat. Similarly, the internal threat to validity for the aspect of maturity could have been minimised by decreasing the time period regarding the experiment for this particular study. In order to minimise the mortality threat, the research could have been based upon a large group of individuals instead of a small group. The research conducted could have avoided the use of baseline tests for minimising the effects of test in the study conducted for this research. The individual who is assigned to collect the data for the study could have been uninformed about the purpose of the study. By doing so, the research could have greatly minimised the threat of external validity and a more reliable outcome could have been gained from this research. Hence, using blind data collection procedure could have been more effective for the specific research. The groups that were selected for the purpose of observation could have been a control group so that it could avoid the threat of internal validity. These are some of the measures that could have been adopted by the authors to minimise the potential threats.

References

Fok, C. C. T., Henry, D., & Allen, J. (2015). Research designs for intervention research with small samples II: Stepped wedge and interrupted time-series designs. Prevention Science, 16(7), 967-977.

Gardner, C. D., Trepanowski, J. F., Del Gobbo, L. C., Hauser, M. E., Rigdon, J., Ioannidis, J. P., … & King, A. C. (2018). Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion: the DIETFITS randomized clinical trial. Jama, 319(7), 667-679.

Kratochwill, T. R. (2015). Single-case research design and analysis: An overview. In Single-Case Research Design and Analysis (Psychology Revivals) (pp. 13-26). Routledge.

Milagro, F. I., Mansego, M. L., De Miguel, C., & Martinez, J. A. (2013). Dietary factors, epigenetic modifications and obesity outcomes: progresses and perspectives. Molecular aspects of medicine, 34(4), 782-812.

St. Clair, T., Cook, T. D., & Hallberg, K. (2014). Examining the internal validity and statistical precision of the comparative interrupted time series design by comparison with a randomized experiment. American Journal of Evaluation, 35(3), 311-327.

Zohrabi, M. (2013). Mixed Method Research: Instruments, Validity, Reliability and Reporting Findings. Theory & practice in language studies, 3(2).