Intermittent Fasting for Improving Metabolic Biomarkers: A Systematic Review By: Rawan Taha

Intermittent Fasting for Improving Metabolic Biomarkers: A Systematic Review

By:

Rawan Taha

ARIZONA STATE UNIVERSITY

JUNE 2023

CHAPTER I
INTRODUCTION

Metabolic syndrome in general and obesity specifically are increasingly common health challenges in the general population. Metabolic syndrome includes conditions such as obesity, hypertension, type 2 diabetes, and dyslipidemia and these are risk factors for cardiovascular disease, the leading cause of death globally (Aleksandrova et al., 2018). The rates of conditions identified under the metabolic syndrome are generally high in the population and this presents a major challenge to public health. People with metabolic syndrome and those at risk can be identified using metabolic biomarkers, inflammation indicators detected even in people who have not developed the health condition yet (Aleksandrova et al., 2018). Addressing metabolic biomarkers in preventative efforts can help reduce the rates of the syndrome and associated health complications.

The research problem identified is the high rates of obesity and other metabolic conditions in the United States. As of 2020, 42.4% of Americans were obese (Hales et al., 2020). Additionally, 49.64% had hypertension with many more undiagnosed cases (Chobufo et al., 2020). Type 2 diabetes mellitus rates are on the rise and so are rates of dyslipidemia. These conditions contributing to the leading cause of death are increasingly common in the United States public and an urgent solution is needed to address the public health problem. Dietary changes are universal approaches to reducing metabolic biomarkers and this research revolves around the question of intermittent fasting.

Reduction of metabolic biomarkers in people at risk of developing metabolic syndrome has been studied by numerous researchers and several have focused specifically on intermittent fasting. Kunduraci and Ozbek (2019) evaluated the effect of intermittent fasting among adults in Turkey. They compared the 16:8 (16 hours of fasting and eight hour window for eating) with continuous energy restriction programs and found that both approaches were effective in reducing metabolic biomarkers (Kunduraci & Ozbek, 2019). Similarly, Rynders et al. (2019) found that people who took intermittent fasting experienced a similar weight loss result as those who undertook continuous energy restrictions. The main difference was that Rynders et al. (2019) conducted systematic review of the literature. From these research articles, intermittent fasting presents the same efficacy as continuous energy restriction diets. The studies also establish the safety of intermittent fasting.

Elsewhere, Cho et al. (2019) found that people who used intermittent fasting achieved a higher level of weight loss than those who used regular diets or continuous diet restrictions. Their research was also a systematic review hence collating many research findings from different studies. Findings from the study by Zouhal et al. (2020) also support these findings. The researchers found that compared to people who did not practice intermittent fasting during Ramadhan, those who engaged in intermittent fasting experienced a higher rate of weight loss and a decrease in interleukin and tumor-necrosis factor (Zouhal et al., 2020). These findings further extend the current research to outline the potential inflammatory pathways for metabolic biomarkers associated with not only obesity but also cancer. The findings that intermittent fasting can reduce metabolic biomarkers and contribute to weight loss have also been corroborated in a Polish study involving older women 65 years and older (Domaszewski et al., 2020). The researchers compared the intermittent fasting 16:8 method with the maintenance of previous feeding habits and concluded that the former was superior in weight loss and reduction of body fat percentage (Domaszewski et al., 2020). From these studies, it is seen that intermittent fasting may be superior to usual diets and continuous energy restriction in weight loss and management of some metabolic biomarkers.

Other studies have focused on intermittent fasting combined with other interventions and 12-hour fasting. Jamshed et al. (2022) evaluated the effectiveness of 12:12 intermittent fasting and found that it resulted in a reduction in weight loss but not body fat. The study was conducted with obese adults in Birmingham, Alabama. Hottenrott et al. (2020) combined intermittent fasting with exercise and alkaline supplements. In both intermittent fasting and control groups, alkaline supplements were associated with better performance running. The intermittent fasting group was more effective in weight reduction (Hottenrott et al., 2020). These findings align with other research findings on intermittent fasting and obesity.

The current research outlines the importance of intermittent fasting but is still deficient. Most of the research focuses entirely on body fat and weight as key biomarkers. Research on other biomarkers is scarce. Moreover, in most of the research articles reviewed, the studies were either short-lived or had a small and non-generalizable sample. Some studies were either limited to women or men which makes them hard to generalize to the public. Also, little research has been conducted on other metabolic biomarkers such as blood pressure, glucose, and cholesterol. Therefore, a gap exists in the research on intermittent fasting and its effectiveness in controlling metabolic biomarkers. Filling this gap presents an opportunity to determine the efficacy of intermittent fasting in reducing the rates of metabolic syndrome and conditions in the general public.

Purpose of Study

The purpose of this study will be to determine the effectiveness of the intermittent fasting 16:8 method on decreasing metabolic biomarkers in overweight and obese individuals. The research will determine whether intermittent fasting can reduce the risk of metabolic syndrome in people who are already identified as overweight or obese.

Research Aims and Hypotheses

Aim: To determine the effectiveness of the intermittent fasting 16:8 method in reducing metabolic biomarkers in overweight people.

Null Hypothesis: Compared to the maintenance of usual dietary habits intermittent fasting is not associated with a significant change in metabolic biomarkers in overweight people.

Alternative Hypothesis: Intermittent fasting reduces metabolic biomarkers in overweight people.

Definitions

Intermittent fasting: A dietary habit where the individual avoids any food intake for 16 hours per day and has an 8-hour window to eat (Cho et al., 2019).

Metabolic biomarkers: Biological indicators of inflammation that include waist circumference, blood glucose, blood pressure, triglycerides, and cholesterol levels (Aleksandrova et al., 2018)

Overweight people: People who have a body mass index (BMI) of 25- 29.5 kg/m2

Delimitations and Limitations

The study will be limited to healthy members of the public who have not been diagnosed with any chronic or terminal illness. It will also be limited to people aged between 18 and 65 years old (adults excluding older adults) with a BMI of 25 and above. The study will be limited to people living in an urban center in the United States and those who can provide informed consent and be available for follow-up. The main limitation of the study is that it may not be generalized to other cities or countries due to the possible unique dietary habits of people in this one city.

CHAPTER II

EVIDENCE ANALYSIS

A review of the literature on Intermittent Fasting for Improving Metabolic Biomarkers is presented in the following evidence analysis tables. The quality of each study was assessed along with the type of study, the demographics of the participants, the interventions, and major research findings. In addition, each table delineates the strengths and limitations of each study. The table was divided into subsections of the author, study design, participant details, methodology, findings, and strengths and limitations.

Author and location

Include first author last name, location (U.S, Italy etc.) and include a superscript citation number.

Study Design

Randomized Control, Experimental, Cross-Sectional, Cohort.

Do not use other systematic reviews or meta-analyses.

Participant Details

Number, gender, age, other identifiers

Method Details

Methods in your own words – length of study, exact intervention details, what were they looking to measure.

Findings

Include all appropriate outcomes, p-values for each and if it reached statistical significance

Strengths and limitations

Consider population size, study design, participants, length of study etc.

Jamshed, H., Steger, F. L., Bryan, D. R., Richman, J. S., Warriner, A. H., Hanick, C. J., & Peterson, C. M. (2022)

Randomized

clinical trial

Adults aged 25 to 75 years with obesity and who received weight-loss treatment through the Weight Loss Medicine Clinic

We screened 656 people and enrolled 90 participants

Conducted between August 2018 and April 2020

14-week study

Intervention entailed giving participants weight loss treatment mainly energy restriction and it was randomized to eTRE plus ER and the control group for 8 hours and more than 12 hours respectively.

Among the 59 completers, it was discovered that eTRE+ER was more

effective for losing body fat and trunk fat than CON+ER.

One strength of the study is that it collected firsthand information regarding the experience of the participants regarding obesity and overweight.

The limitations of the study is short duration, use of self-report to assess patient condition.

Cho, Y., Hong, N., Kim, K. W., Cho, S. J., Lee, M., Lee, Y. H., & Lee, B. W. (2019)

Randomized controlled trials and controlled clinical trials

No participants were involved because it was a secondary literature analysis

The method entailed selecting articles with periodic fasting, periodic data, and modified fating and evaluating the trend in these articles.

The findings show that after fasting for 12 hours lipolysis starts in the fat tissues. Skipping breakfast is associated with increased stress.

One limitation is that the studies used were diverse, which makes it to have a broad scope that is not narrowed.

Chobufo, M. D., Gayam, V., Soluny, J., Rahman, E. U., Enoru, S., Foryoung, J. B., & Nfor, T. (2020)

Cross-sectional study design

5000 persons in 15 counties per year.

The methods entails conducting a NHANES by the CDC. The records helped to get systolic and diastolic blood pressure readings of participants.

The findings show that education level determined one’s level of hypertension. Increasing age, obesity, being a man, and those with diabetes were at risk of hypertension.

One strength is that blood pressure readings were done at the same time. One limitation is that two years’ time period is very small or studying changes in habits.

Domaszewski, P., Konieczny, M., Pakosz, P., Bączkowicz, D., & Sadowska-Krępa, E. (2020)

Randomized Control

group of 45 women over 60 years

The interventions entailed assessing and tracking the participants’ body composition and BMI. It also entailed measuring the mental state and ankle-branchial index.

The findings showed that the body mass of the experimental group reduced by 2 kg. Skeletal body mass did not change significantly.

One limitation of the study is that it entailed few participants, which cannot help in drawing reputable and reliable findings.

Hales, C. M., Carroll, M. D., Fryar, C. D., & Ogden, C. L. (2020)

Cross-sectional study design

Adults aged 20 and over

1999-2000 through 2015-2016

The study identified a significantly increasing trend in obesity

One strength of the study is the use of bulk historical data.

One limitation is reliance on historical data, whose authenticity and reliability cannot be determined

Aleksandrova, K., Mozaffarian, D., & Pischon, T. (2018).

Information is from secondary sources

Both adults and children with obesity

The time of the study is not specified as most information is from secondary sources

The study identified the role of biomarkers in obesity related cases and their association in cardiometabolic diseases.

One strength is that the research is broad and comparative.

One weakness is that most of the information used is not firsthand.

Hottenrott, K., Werner, T., Hottenrott, L., Meyer, T. P., & Vormann, J. (2020).

Clinical trials

80 overweight subjects of age 45.5 ± 7.8 years

All participants were tested for 12 weeks

The study determined the combined effects of IF, exercise training and alkaline supplementation in overweight participants on body composition and running performance

The advantages of this study are;

It took a short reasonable time and the data was first hand hence very accurate.

Kunduraci, Y. E., & Ozbek, H. (2020).

Randomized controlled trial

Metabolic syndrome patients, aged 18–65 years in Istanbul Turkey

12 weeks .

The study found out that technique used to achieve energy restriction, in either intermittent or continuous, alleviates the metabolic syndrome biomarkers activated by weight loss.

One limitation is the study was on metabolic syndrome patients hence hot giving accurate data to be used for healthy people.

Rynders, C. A., Thomas, E. A., Zaman, A., Pan, Z., Catenacci, V. A., & Melanson, E. L. (2019).

Randomized trials

11 adults with overweight or obesity (BMI ≥ 25 kg/m2)

8 weeks

The available evidence indicates that Intermient Energy Restrictions paradigms cause equal weight reduction when compared to Continuous Energy Restrictions, with no changes in weight or body fat loss across groups being observed in 9 out of 11 studies assessed.

one limitation of this research is that it uses few participants.

Zouhal, H., Bagheri, R., Ashtary-Larky, D., Wong, A., Triki, R., Hackney, A. C., & Abderrahman, A. B. (2020).

Experimental method

28 males with obesity

30 days

The results of this study show that fasting during Ramadan reduced systemic inflammatory biomarkers in obese males and there was no detrimental effects on the indicators of liver and renal function.

One advantage of this study is that it was carried out during a time when fasting was mandatory hence increasing data accuracy.

Ogden, C. L., Carroll, M. D., Kit, B. K., & Flegal, K. M. (2014)

National survey.

9120 participants

Between 2003-2012 (10 years)

According to the study,  there have been no significant changes in obesity prevalence in youth or adults between 2003-2004 and 2011-2012. Obesity prevalence remains high and thus it is important to continue surveillance.

The advantage of this article is that it used large amount of data hence being more accurate.

Ravussin, E., Beyl, R. A., Poggiogalle, E., Hsia, D. S., & Peterson, C. M. (2019).

Clinical trial

11 overweight adults

4 days

Meal-timing interventions facilitate weight loss primarily by decreasing appetite rather than by increasing energy expenditure

One limitation of this study is that it took a very short time hence may be inaccurate.

Harvey, J., Howell, A., Morris, J., & Harvie, M. (2018).

Randomized Clinical trials

 Study 1; 44 women on Intermittent Energy Restrictions for 6 months

Study 2; 72 women on two types of Intermitent Energy Restrictions for 4 months

6 months and 4 months

According to this study, intermittent dieting could be an effective way to achieve weight loss without having to worry about calorie compensation.

One limitation about this study is that it requires more time for credible results.

Jakubowicz, D., Barnea, M., Wainstein, J., & Froy, O. (2013

Randomized experiments

Overweight and obese women (BMI 32.4 ± 1.8 kg/m2) with metabolic syndrome

12 weeks

The study concluded that High-calorie breakfasts are advantageous and may be a practical substitute for managing obesity and metabolic syndrome at dinnertime.

The advantage of this study is that it specific on the research population hence its findings are useful for that population.

Viegener, B. J., Renjilian, D. A., McKelvey, W. F., Schein, R. L., Perri, M. G., & Nezu, A. M. (1990).

Randomized controlled trials

85 obese women

12 months

From the study, the group that did intermittent fasting lost weight faster than those that did regular treatment.

The advantage about this study is that it compares two populations over different lengths of time.

Acosta-Rodríguez, V. A., de Groot, M. H., Rijo-Ferreira, F., Green, C. B., & Takahashi, J. S. (2017

Controlled experiment

8-week-old male mice

2 weeks

From the study, concentrating their food intake and suddenly boosting their wheel-running activity during the rest period, mice under Caloric Restriction self-imposed a temporal component, exposing previously unappreciated linkages between feeding, metabolism, and behavior.

One limitation is the time allocated was little hence can be led to inconclusive results.

Hoddy, K. K., Gibbons, C., Kroeger, C. M., Trepanowski, J. F., Barnosky, A., Bhutani, S., … & Varady, K. A. (2016).

Random trials

74 obese people between the age of 25-65 years.

8weeks

These results imply that the effectiveness of an 8-week ADF regimen for weight loss may be influenced by the absence of a compensatory rise in hunger along with an increase in fullness sensations.

One limitation about this study is that it is population specific

Julia, C., Péneau, S., Andreeva, V. A., Méjean, C., Fezeu, L., Galan, P., & Hercberg, S. (2014).

Cohort study

46435 people above 18 years

10 years

From the study, when loosing weight, it is essential to maintain a dietary balance.

One strength of this research is that it takes a long time, hence being more accurate.

Horne, B. D., Muhlestein, J. B., & Anderson, J. L. (2015).

A systemic review of public literature on randomized clinical trials

Both male and female

Literature from 2015

There are few literature sources on the randomized clinical trials hence need for more research

Limitations of this research is that it is not conclusive.

Carter, S., Clifton, P. M., & Keogh, J. B. (2018

Randomized noninferiority trial

137 men and women with type 2 diabetes

12 months

In patients with type 2 diabetes, intermittent calorie restriction is comparable to continuous energy restriction in terms of effectiveness in lowering HbA1c.

One strength of this research is that it has updated supporting evidence which makes it valid.

CHAPTER III

METHODS

This systematic review was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards, which guides in the selection of articles for use in information extraction. PRISMA helped in assessing, locating, and incorporating the information that is available into the report. It is worth noting that the PICO approach that entails the use of population, intervention, comparison, and outcome of treatment intervention. The PICO approach helped to develop a model as outlined in the table below. The study was used to determine the impact of intermittent fasting of about 12 to 16 hours could help the obese and overweight to manage their weight. The impact of the intervention was traced across several articles, which showed the impact of intermittent fasting on the metabolic activity rate. The rate of effectiveness of intermittent fasting was evaluated among obese and overweight individuals that participated in the studies. It is worth noting that the studies that were only included were those that were obese or overweight with a BMI of 25 or above.

Throughout this systematic review, the flow diagram of PRISMA located below, determined the guidelines and workflow that was used to analyze and review each piece of literature. The flow diagram also contains information about how each piece of literature was incorporated into this review in terms of locating, assessing, and appropriateness. Research studies that fell under the categories of either meta-analyses or systematic reviews were used to find material or data that was capable of meeting the criteria of inclusion. However, meta-analyses and systematic reviews were not included in finding necessary data or information for inclusion and were excluded from this review.

The core search terms used in the systematic review include “obese”, “obesity”, “intermittent fasting”, “dieting,” fasting and many others. The major databases that were used include PubMed, Google Scholar, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL).

The research articles that were used in this review had to meet the standards in The Academy of Nutrition and Dietetics (AND) Quality Criteria Checklist for Primary Articles. For studies that passed the checklist, the studies were incorporated into the Academy of Nutrition and Dietetics (AND) Evidence Analysis Table (Chapter 2). The tables outlined each research study and summarized the outcomes. It is worth noting that the tables provided a methodical arrangement of each research study by outlining the author(s), year of publication, sample characteristics, treatment and control groups, intervention/exposure examined, results, and strengths and limitations.

PICO Inclusion Criteria

PICO

Potential Search Terms

Population:

Those with obesity and overweight (of BMI 25 or above)

Intervention:

Intermittent fasting for 8-16 hours.

Comparison (you may not have):

Those not fasting but following a hypocaloric diet

Outcome(s):

Reduced body weight and BMI.

Search Terms Used for Systematic Review and Evidence Analysis

Database

Date of search

Search String

Filters Used

Number of results

Number of results after removing duplicates

After reviewing for quality, articles kept

PubMed

4-June-23

“overweight”, “obese” and intermittent fasting

5 years, clinical trial, randomized controlled trial

36

34

9

Google Scholar

5-June-23

“overweight”, “obese” and intermittent fasting

5 years, clinical trial, randomized controlled trial

22,700

11,470

13

CINAHL

15-June-23

“overweight”, “obese” and intermittent fasting

5 years, clinical trial, randomized controlled trial

97

80

6

PRISMA 2009 Flow Diagram

Screening

Included

Eligibility

Identification

Records after duplicates removed
(n = 30)

Records screened
(n = 30)

Records excluded
(n = 15)

Additional records identified through other sources
(n = 2)

Records identified through database searching
(n = 28)

Full-text articles excluded (n=5)

1 excluded for lack of full-text article

3 excluded for no intervention in the research methods

2 excluded for unclear nutrition interventions

Full-text articles assessed for eligibility
(n = 15)

Studies included in the systematic review
(n = 10)

CHAPTER IV

RESULTS

The search was conducted with three databases: Google Scholar, PubMed, and CINAHL. The search was conducted with terms such as intermittent fasting, metabolic biomarkers, overweight, obese, obesity, fasting, BMI, and blood glucose. For current research on the topic, studies were limited to those published from 2015 to 2023. The studies were also limited to those with interventional research methodology only. This excludes cross-sectional studies and systematic reviews. Studies were also selected based on availability of full-text articles, publication in English language, and the researcher’s evaluation of quality using the JBI critical appraisal checklists. As shown in the PRISMA diagram, a total of 28 articles were selected from the database and 2 from an open Internet search for a total of 30 articles included for screening. The PRISMA diagram shows that after screening, 15 records were excluded. After assessment and critical appraisal, an additional 6 records were excluded, remaining with only 9 records that met the inclusion criteria and were assessed as meeting the quality requirements for this study.

The studies prioritized in this review were the randomized controlled trials (RCTs). Seven of the nine articles included in this review were RCTs. Domaszewski et al. (2020) recruited women over 60 years and randomized them to an intervention group of 16 hour complete abstinence from food and the control group followed eating plans reflecting their previous eating habits. Zouhal et al. (2020) randomized males with obesity during the Ramadan fasting period to intervention (15-16 hours of fasting) and control group (no fasting). Additionally, Jamshed et al. (2022) recruited people with obesity in a weight loss clinic and randomized them to 16 hours fasting (intervention) and a self-selected non-fasting diet. Kunduraci and Ozbek (2020) randomized researchers to intermittent fasting (16:8) and continuous energy restriction. Carter et al. (2018) specifically targeted people with type 2 diabetes and randomized the participants to intermittent fasting and continuous energy restriction. Hottenrott et al. (2020) randomized overweight individuals to intermittent fasting and non-intermittent fasting. In each group, participants were further randomized to taking alkaline supplement and placebo for a total of four participant groups (Hottenrott et al., 2020). Ravussin et al. (2019) conducted a randomized cross-over trial with intervention group being an 18-hour daily fasting period.

Results from the RCTs favor the use of intermittent fasting to lose weight as well as improve other metabolic biomarkers. Domaszewski et al. (2020) reported an approximate average of 2 kg weight loss for the experimental group in six weeks for women aged 60 years and above. Similarly, compared to a self-selected non-fasting meal, obese adults following the 16:8 intermittent fasting plan lost 6.3 kg on average over 14 weeks while the control group lost an average 4 kg (Jamshed et al., 2022). Additionally, Hottenrott et al. (2020) concluded that combining intermittent fasting with alkaline supplement results in more weight loss than intermittent fasting alone.

In addition to weight loss, metabolic biomarkers were also improved. Zouhal et al. (2020) realized a decline in interleukin-6 and tumor necrosis factor-alpha, two important inflammatory biomarkers. When compared to continuous energy restriction, intermittent fasting produced similar results and was not inferior to continuous energy restriction interventions (Kunduraci & Ozbek, 2020; Carter et al., 2018). Ravussin et al. (2019) recorded reduced desire to eat, increased metabolic flexibility, and increased fullness in the intermittent fasting group.

The other two studies included in this review were a single-group pre- and post-test study, and an analysis of two previous controlled trials. Hoddy et al. (2016) assessed changes in weight, fat mass, and resting metabolic rates before and after an eight-week alternate-day fasting intervention. They reported an average decrease of 3.9 kg in weight, 2.2 kg in fat mass, and resting metabolic rate of 104 kcal/day (Hoddy et al., 2016). Harvey et al. (2018) examined the outcomes of two previous RCTs involving obese women and reported an average 7.4% weight loss.

The risk of bias in these studies is moderate. In the RCTs, blinding was not possible since participants had to be aware of the diet they are following for adherence. This is a potential risk of bias due to the possible changes in lifestyle accompanied by the dietary interventions. The study with a high risk of bias is Zouhal et al. (2020) because there was no true randomization; participants were assigned to groups based on whether they were willing to participate in Ramadhan fasting or not. In the non-RCT, Hoddy et al. (2016) used a cross-over trial method which reduces the risk of bias. These studies present a quality of research and credible findings.

CHAPTER V

DISCUSSION

The purpose of this review was to research the available interventional studies on intermittent fasting and its impact on metabolic biomarkers. The researcher hypothesized that adhering to an intermittent diet of 16 hours fasting and eight hours eating window (16:8) would reduce metabolic biomarkers associated with obesity, diabetes, cardiovascular diseases, and inflammation. Metabolic biomarkers can indicate the current health problems as well as health problems that the individual is at risk of developing. The aim of this study was to assess the association between intermittent fasting and presence of metabolic syndrome.

The majority of studies included in this review supported the hypothesis that intermittent fasting is associated with lower risk of metabolic syndrome. Weight loss is one of the primary indicators of better health outcomes in people with obesity and at risk of cardiovascular diseases and diabetes. Studies in this review have shown that intermittent fasting can effectively and safely be used to lose weight by presenting significant weight loss in intervention groups compared to control groups (Jamshed et al., 2022). Weight loss is important because it helps in reducing blood pressure as well as reducing the amount of blood glucose and cholesterol. Even modest weight loss significantly reduces the risk of developing cardiovascular conditions and diabetes (Powell-Wiley et al., 2021). Therefore, this evidence on weight loss is significant to recommend using the 16:8 intermittent fasting approach to people struggling with obesity.

Moreover, the benefits of intermittent fasting to the overall metabolic health of the individual have been highlighted. Intermittent fasting may be challenging especially in the initial days due to changes in body metabolism and patterns. However, it has been associated with better satiety and metabolic flexibility (Ravussin et al., 2019). This is a benefit in lifestyle adjustments in that the individual may maintain a healthier lifestyle with intermittent fasting. Its maintenance of fullness and improved metabolism in fasting individuals can improve the activity of beta cells in the pancreas and improve glucose management, enhancing glycemic control (Brown et al., 2021). These results essentially indicate that intermittent fasting is beneficial to the body as it improves metabolic function. This is the connection to metabolic biomarkers. The decline in interleukin-6 and tumor necrosis factor-alpha presents a potential connection between metabolism and inflammation, including diseases such as cancer (Zouhal et al., 2020). The protective potential of intermittent fasting, therefore, goes beyond obesity, diabetes, and cardiovascular diseases and may include other forms of inflammation. Further research on the causal connection between intermittent fasting and inflammatory conditions is needed.

The main benefit of intermittent fasting is that it does not require restrictions on the type of food groups taken. Many other diets target a specific food group and seek to reduce its consumption. An example is the low-carbohydrate diet popularly known as ketogenic diet (Carneiro et al., 2021). The risk of diets that target specific food groups is that they upset the balance of one’s diet and may lead to nutritional deficiencies. In intermittent fasting, the open window for eating can be used to feed on the usual food groups. Nevertheless, the individual must still reduce consumption of unhealthy foods such as ultra-processed, high fat, and high sugar foods when doing intermittent fasting (Domaszewski et al., 2020). This benefit of intermittent fasting may have significant impact on adherence, a topic of further research in other reviews.

This review had several strengths and limitations as well. On the one hand, the review only included interventional studies. This restriction in studies included enhances the validity and reliability of reported findings. The studies included were also limited to the current research studies published in peer-reviewed journal articles, producing a high level of evidence. On the other hand, only a few studies focusing on metabolic biomarkers other than body weight were included. There is scarcity of research on the relationship between intermittent fasting and the wide variety of metabolic biomarkers. More studies are needed to dive deeper into the correlation of intermittent fasting and other metabolic biomarkers other than obesity.

CHAPTER VI

CONCLUSION

This review presented the current scientific evidence of the connection between intermittent fasting and metabolic biomarkers. The purpose of this review was to determine whether current research supports the use of intermittent fasting diets in weight loss and managing metabolic syndrome. Majority of the studies considered in the review are randomized controlled trials and have reported significant weight loss with intermittent fasting. Some of the studies have also reported better metabolism, satiety, and decline in inflammatory metabolic biomarkers, indicating the potential for the diet to reduce risk of inflammatory condition. At this time, the most credible and reliable evidence supports intermittent fasting for weight loss in the short-term. This is beneficial for glycemic control, managing blood pressure, and reducing level of cholesterol in the body hence reducing the complications of cardiovascular and other chronic conditions. Further research on the long-term effectiveness of intermittent fasting and its efficacy in reducing inflammatory biomarkers is required.

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