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Intermittent fasting (IF) is an umbrella term for various diets that cycle between a period of fasting and non-fasting during a defined period. Intermittent fasting can also be used with calorie restriction for weight loss.
- 1 Practice and variations
- 2 Research
- 3 See also
- 4 References
Practice and variations
Some people may use intermittent fasting to diminish caloric intake and lose weight. Preliminary research indicates that intermittent fasting may affect risk factors for some diseases.
Intermittent fasting protocols can be grouped into 2 categories: whole-day fasting and time-restricted feeding (TRF).
- Whole-day fasting involves regular one-day fasts. The strictest form would be Alternate day fasting (ADF). This involves a 24-hour fast followed by a 24-hour non-fasting period. The 5:2 diet allows the consumption of 500–600 calories on fasting days.
- Time-restricted feeding (TRF) involves eating only during a certain number of hours each day. A common form of TRF involves fasting for 16 hours each day and only eating during the remaining 8 hours, typically on the same schedule each day. A more liberal practice would be twelve hours of fasting and a twelve-hour eating window, or a stricter form would be to eat one meal per day, which would involve around 23 hours of fasting per day.
Recommendations vary on what can be consumed during the fasting periods. Some would say only water, others would allow tea or coffee (without milk or sugar) or zero-calories drinks with artificial sweeteners. Yet others would allow “modified fasting” with limited caloric intake (e.g., 20% of normal) during fasted periods rather than none at all.
The 5:2 diet became popular in the UK in 2012 after the BBC2 television Horizon documentary Eat, Fast and Live Longer. Via sales of best-selling books, it became widely practiced.
According to NHS Choices as of 2012, people considering the 5:2 diet should first consult a physician, as fasting can sometimes be unsafe. In the UK, the tabloid press reported on research claiming the 5:2 diet could reduce the risk of breast cancer, improve brain and immune functions, or extend lifespan, but there is inadequate evidence for such statements. A news item in the Canadian Medical Association Journal expressed concern that promotional material for the diet showed people eating high-calorie food such as hamburgers and chips, and that this could encourage binge eating since the implication was that “if you fast two days a week, you can devour as much junk as your gullet can swallow during the remaining five days”.
A 2014 review described that intermittent fasting has not been studied in children, the elderly, or the underweight, and could be harmful in these populations. It also suggested that people choosing to fast for periods of time greater than 24 hours should be monitored by a physician, as changes to the gastrointestinal system or circadian rhythm can occur. The review concluded that fasting is unlikely to have much effect on conditions other than obesity, such as aging or other chronic conditions, unless combined with long-term calorie restriction and a plant-based diet, such as the Mediterranean diet.
According to another 2014 review, intermittent fasting can lead to weight loss, though long-term calorie restriction can lead to slightly more weight loss compared to intermittent fasting. Intermittent fasting has been found in healthy and obese adults to reduce basal insulin, triglycerides, and blood glucose in fasting periods shorter than 24 hours. A 2014 review showed that intermittent fasting may reduce inflammation mechanisms and possibly affect cancer risk. Reductions in weight, improvements in cardiovascular and metabolic variables, such as fat mass, LDL cholesterol, triglycerides, and C-reactive protein in non-obese individuals have been recorded. Laboratory and preliminary human research indicates that intermittent fasting may influence metabolism of different food sources.
- Calorie restriction
- Henry S. Tanner (doctor)
^ Mager, D. E (2006). “Caloric restriction and intermittent fasting alter spectral measures of heart rate and blood pressure variability in rats”. The FASEB Journal. 20 (6): 631–7. doi:10.1096/fj.05-5263com. PMID 16581971.
^ Patterson, R. E; Laughlin, G. A; Lacroix, A. Z; Hartman, S. J; Natarajan, L; Senger, C. M; Martínez, M. E; Villaseñor, A; Sears, D. D; Marinac, C. R; Gallo, L. C (2015). “Intermittent Fasting and Human Metabolic Health”. Journal of the Academy of Nutrition and Dietetics. 115 (8): 1203–1212. doi:10.1016/j.jand.2015.02.018. ISSN 2212-2672. PMC 4516560 . PMID 25857868.
^ a b c Mattson, M. P; Longo, V. D; Harvie, M (2017). “Impact of intermittent fasting on health and disease processes”. Ageing Research Reviews. 39: 46–58. doi:10.1016/j.arr.2016.10.005. PMC 5411330 . PMID 27810402.
^ a b Varady, K. A (2011). “Intermittent versus daily calorie restriction: Which diet regimen is more effective for weight loss?”. Obesity Reviews. 12 (7): e593–601. doi:10.1111/j.1467-789X.2011.00873.x. PMID 21410865.
^ Fisher, Roxanne (1 June 2016). “What is the 5:2 diet?”. BBC GoodFood, Worldwide.
^ a b c d Fleming, Amy (27 January 2015). “Fasting facts: is the 5:2 diet too good to be true?”. The Guardian. Retrieved 18 January 2018.
^ Rothschild, Jeff; Hoddy, Kristin K; Jambazian, Pera; Varady, Krista A (2014). “Time-restricted feeding and risk of metabolic disease: A review of human and animal studies”. Nutrition Reviews. 72 (5): 308–18. doi:10.1111/nure.12104. PMID 24739093.
^ Moro, Tatiana; Tinsley, Grant; Bianco, Antonino; Marcolin, Giuseppe; Pacelli, Quirico Francesco; Battaglia, Giuseppe; Palma, Antonio; Gentil, Paulo; Neri, Marco; Paoli, Antonio (2016). “Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males”. Journal of Translational Medicine. 14 (1): 290. doi:10.1186/s12967-016-1044-0. PMC 5064803 . PMID 27737674.
^ Stote, KS; Baer, DJ; Spears, K; Paul, DR; Harris, GK; Rumpler, WV; Strycula, P; Najjar, SS; Ferrucci, L; Ingram, D. K.; Longo, D. L.; Mattson, M. P. (2007). “A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults” (PDF). The American Journal of Clinical Nutrition. 85 (4): 981–8. PMC 2645638 . PMID 17413096.
^ “How to diet”. Live Well – NHS Choices. UK National Health Service. 9 December 2011. Retrieved 10 February 2014.
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^ Healy A (11 June 2013). “Dietitians warn against fad diets”. Irish Times.
^ Mosley, Michael (5 September 2012). “Eat, Fast & Live Longer”. Horizon. Episode 49×03. BBC. 2. Retrieved 10 February 2014.
^ “The UK’s Hot New 5:2 Diet Craze Hits The U.S. – Weight Loss Miracle?”. Forbes. 17 May 2013. Retrieved 10 February 2014.
^ “News analysis: Does the 5:2 intermittent fasting diet work?”. Health News. UK National Health Service – NHS Choices. May 2013. Retrieved 23 November 2016.
^ “Could 5:2 diet play a role in preventing breast cancer?”. NHS Choices. 17 June 2016.
^ Collier, R (2013). “Intermittent fasting: The science of going without”. Canadian Medical Association Journal. 185 (9): E363–4. doi:10.1503/cmaj.109-4451. PMC 3680567 . PMID 23569168.
^ a b c Longo, Valter D; Mattson, Mark P (2014). “Fasting: Molecular Mechanisms and Clinical Applications”. Cell Metabolism. 19 (2): 181–92. doi:10.1016/j.cmet.2013.12.008. PMC 3946160 . PMID 24440038.
^ Barnosky, Adrienne R; Hoddy, Kristin K; Unterman, Terry G; Varady, Krista A (2014). “Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: A review of human findings”. Translational Research. 164 (4): 302–11. doi:10.1016/j.trsl.2014.05.013. PMID 24993615.
^ a b Anton, Stephen D; Moehl, Keelin; Donahoo, William T; Marosi, Krisztina; Lee, Stephanie A; Mainous, Arch G; Leeuwenburgh, Christiaan; Mattson, Mark P (2017). “Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting”. Obesity. doi:10.1002/oby.22065. PMID 29086496.
^ Mattson, Mark P.; Allison, David B.; Fontana, Luigi; Harvie, Michelle; Longo, Valter D.; Malaisse, Willy J.; Mosley, Michael; Notterpek, Lucia; Ravussin, Eric (2014-11-25). “Meal frequency and timing in health and disease”. Proceedings of the National Academy of Sciences of the United States of America. 111 (47): 16647–16653. doi:10.1073/pnas.1413965111. PMC 4250148 . PMID 25404320.
^ Horne, Benjamin D; Muhlestein, Joseph B; Anderson, Jeffrey L (2015-08-01). “Health effects of intermittent fasting: hormesis or harm? A systematic review”. The American Journal of Clinical Nutrition. 102 (2): 464–470. doi:10.3945/ajcn.115.109553. ISSN 0002-9165.