Types of participants
This review will consider studies that include free-living (not hospitalized) male and female adults aged 18 years and over (adults of any age will be included; however age will be considered as a potential moderator) who are overweight or obese (i.e. have a BMI greater than or equal to 25 or 30). Participants will be excluded if they have secondary or syndromic forms of obesity or are diabetic, undergoing bariatric surgery, pregnant or breast feeding, and taking medication associated with weight loss (e.g. orlistat, metformin) or weight gain (e.g. steroids, antipsychotics).
Types of intervention(s)/phenomena of interest
This review will consider studies that evaluate intermittent fasting interventions (defined as consumption of 800* kcal or less on at least one day, but no more than six days in a calendar week) that follow participants for at least 12 calendar weeks from the start of the intervention.
*as there is no accepted formal definition of "fasting" - the NICE upper limit for a very low calorie diet will be used in this review.5
Types of comparators
Interventions will be compared to control (no intervention) or usual care (which is likely to consist of advice to continuously follow a reduced calorie diet, which is usually around 25% of recommended energy intake).
Types of outcomes
Primary outcome: any objective, validated measure of adiposity: measured (not self-reported) body mass; body mass index; waist circumference; skin fold thickness; bio-impedance; hydrostatic or BodPod measures; and dual X-ray absorptiometry (DXA) or magnetic resonance imaging (MRI) scans. Secondary outcomes: adverse events; quality of life; disease risk markers (e.g. blood glucose, cholesterol, blood pressure); diet and physical activity.
Types of studies
This review will only consider randomized or pseudo randomized controlled trials.
The search strategy aims to find both published and unpublished studies. A three-step search strategy will be utilized in this review. An initial limited search of MEDLINE and CINAHL will be undertaken followed by analysis of the text words contained in the title and abstract, and of the index terms used to describe the relevant articles. A second search using all identified keywords and index terms will then be undertaken across all included databases. Thirdly, the reference list of all identified reports and articles will be searched for additional studies. Studies in English language, published since database inception will be considered for inclusion in this review.
The databases to be searched include:
Medline via OVID Host
Embase via OVID
Cinahl via EBSCO Host
Cochrane Central Register of Controlled Trials (CENTRAL)
The search for unpublished studies will include:
Initial keywords to be used will be intermittent fasting or periodic fasting, alternate day fasting or intermittent calorie restriction, and overweight or obesity. A provisional full search strategy (to be confirmed following the initial search) is presented in Appendix I.
Assessment of methodological quality
Papers selected for retrieval will be assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) (Appendix II). Any disagreements that arise between the reviewers will be resolved through discussion, or with a third reviewer.
Data will be extracted from papers included in the review using the standardized data extraction tool from JBI-MAStARI (Appendix III). The data extracted will include specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives.
Quantitative data will, where possible be pooled in statistical meta-analysis using JBI-MAStARI. All results will be subject to double data entry. Effect sizes expressed as odds ratio (for categorical data) and weighted mean differences (for continuous data) and their 95% confidence intervals will be calculated for analysis. Heterogeneity will be assessed statistically using the standard I-squared and tau-squared. Where possible, subgroup analyses will also be conducted based on baseline weight status of participants (i.e. overweight [BMI: 25-29], obese [BMI: 30-39] & morbidly obese [BMI 40+]); gender; age; length of study and IF approach. Where statistical pooling is not possible the findings will be presented in narrative form including tables and figures to aid in data presentation where appropriate.
Conflicts of interest
The authors have no conflicts of interest to declare.
The authors would like to thank Teesside University for funding this review.
1. World Health Organization. Overweight
factsheet. 2015. [Internet]. [Cited in May 2015]. Available from: http://www.who.int/mediacentre/factsheets/fs311/en/
2. Scarborough P. Bhatnagar P, Wickramasinghe KK, Allender S, Foster C, Rayner M. The economic burden of ill health due to diet, physical inactivity, smoking, alcohol and obesity
in the UK: an update to 2006?07 NHS costs. J Public Health. 2011; 33(4): 527-535.
3. Butland B, Jebb S, Kopelman P, McPherson K, Thomas S, Mardell J, Parry V. Tackling obesities: future choices. Foresight Programme of the Government Office for Science. 2007. Available from: https://www.gov.uk/government/collections/tackling-obesities-future-choices
4. Laddu D, Dow C, Hingle M, Thomson C, Going S. A review of evidence-based strategies to treat obesity
in adults. Nutr Clin Pract. 2011; 26(5): 512-525.
5. NICE. Obesity
: identification, assessment and management of overweight
in children, young people and adults. 2014. [Internet]. [Cited on August 28, 2015]. Available from: http://www.nice.org.uk/guidance/cg189
6. Antoni R, Johnston KL, Collins AL, Robertson MD. The Effects of Intermittent Energy Restriction on Indices of Cardiometabolic Health, Research in Endocrinology. 2014; Article ID 459119
7. Horne BD, Muhlestein JB, Anderson JL. Health effects of intermittent fasting
: hormesis or harm? A systematic review. Am J ClinNutr 2015;102(2): 464-470.
8. British Dietetic Association. Food fact sheets: detox diets. 2014. [Internet]. [Cited on August 28, 2015]. Available from: https://www.bda.uk.com/foodfacts/detoxdiets.pdf
9. NHS choices. News analysis: Does the 5:2 fast diet work? NHS choices: your health your choices. 2013. Available from: http://www.nhs.uk/news/2013/01January/Pages/Does-the-5-2-intermittent-fasting-diet-work.aspx
10. Brown JE, Mosley M, Aldred S. Intermittent fasting
: A dietary intervention for prevention of diabetes and cardiovascular disease?. Br J DiabVasc Dis.2013;13(2): 68-72.
Appendix I: initial list of search terms
intermittent fast* OR
alternate-day fast* OR
intermittent energy restriction OR
intermittent calorie restriction OR
fasting calorie restriction intervention OR
intermittent restrictive diet OR
very low calorie diet OR
periodic fasting OR
body mass OR
body size OR
body weight OR
Weight gain OR
Weight maintenance OR
Weight management OR
adverse events OR
blood glucose OR
blood pressure OR
body mass index OR
dxa (scan) OR
physical activity OR
quality of life/QoL OR
skin-fold/skin fold thickness OR
waist circumference OR
Appendix II: Appraisal instruments
MAStARI appraisal instrument
Appendix III: Data extraction instruments
MAStARI data extraction instrument