What is Intermittent Fasting

What is intermittent fasting?
Intermittent Fasting (IF) is an eating plan based on when you eat rather than only what you eat. There are different variations of intermittent fasting, but all are based around the idea of restricting eating to limited periods of time. Research has shown this eating pattern to be very beneficial in weight loss and also for overall health.
How do you intermittently fast?
No food is allowed during a fasting period but water, coffee, and tea are permitted. Other non-caloric items may be allowed depending on the type and goal of your individual fast. Not everyone who does intermittent fasting follows the exact same protocol. An example of a common schedule includes a 16:8 split, where 16 hours in a day is spent fasting, and any eating must occur during the remaining 8 hour time span. Likewise, in an 18:6 split, 18 hours is spent fasting, and feeding is within the remaining 6 hours. Some may prefer to have the eating frame earlier in the day, and some later (ex. skipping breakfast). Other variations include eating only one time each day or even fasting for longer custom periods of time, such as multiple days in a row. In all of these methods, there is a cycle of longer fasting period followed by shorter feeding time.
What are the benefits?
Weight loss: By reducing the number of meals throughout the day, intermittent fasting typically leads to a reduction in calories, but recent research has shown that fasting can lead to greater weight and fat loss than simple calorie restriction alone. (1) During a fast your body adjusts hormone levels, making stored body fat more accessible to burn. Typically, after 12 hours of food intake cessation, there is a switch from fat/cholesterol synthesis and fat storage to ketone production. This change begins to burn fat while at the same time preserving muscle mass and function. This means that intermittent fasting regimens that activate this metabolic switch can improve body composition. (8) While weight loss may be the most common reason people seek out intermittent fasting, the benefits go far beyond simply losing weight. Insulin resistance: Diabetes is a major health concern throughout Singapore today, with MOH declaring a “War on Diabetes” in 2016. Intermittent fasting helps regulate insulin levels, making it an excellent way to protect against Type 2 Diabetes. A study in 2018 at the University of Alabama showed that within a group of prediabetic obese men, the participants with a feeding window limited to 6 hours a day showed dramatically lower insulin levels after 5 weeks than those eating the exact same meals over a 12 hour span. (2) Heart health: The participants in that same study also showed a significant reduction in blood pressure over the 5 week period. (2) Intermittent fasting may also provide cardiac protection even after cardiovascular events. In observational studies, Muslims with a history of ischemic event show a reduced incidence of decompensated heart failure during the fasting month of Ramadan when compared with other times of the year. (3) Ketosis is common during intermittent fasting, and one recent study showed that over a year of continuous care in patients with Type 2 Diabetes which included nutritional ketosis, most biomarkers of Cardiovascular Disease were reduced. (9) Brain health: According to a study in Nature Reviews Neuroscience, when discussing the depletion of liver glycogen stores and a switch to production of ketones in the state of fasting and extended exercise: “Such metabolic switching impacts multiple signalling pathways that promote neuroplasticity and resistance of the brain to injury and disease.” (4) Multiple studies have also shown that caloric restriction can have a positive impact on memory and cognition. (5, 6) Inflammation: An article in Cell states that hypocaloric diets or fasting regimens are associated with improved outcomes of metabolic, autoimmune, and inflammatory diseases in humans, including NAFLD (Nonalcoholic Fatty Liver Disease). According to this study, “Monocytes are important producers of pro-inflammatory cytokines and play a critical role in the induction and maintenance of inflammation.” The study identified a drastic effect from short-term and intermittent fasting on the level of these monocytes in the blood and tissues. Since monocytes are important producers of inflammatory cytokines, it is conceivable that “repetitive short-term fasting or caloric restriction decreases susceptibility to pathological inflammatory disease.” (7) Other benefits of intermittent fasting may include decreased total and LDL cholesterol, improved sleep, cellular repair, protection against neurodegenerative diseases, increased lifespan, and more.
While intermittent fasting has seen an increase in interest lately, the concept is not new. In fact, this eating pattern has been practiced throughout human history for both religious and therapeutic reasons. The effects of time restricted eating have only recently started to be studied and understood by modern science, but the positive effects have already shown to be wide ranging and significant. Intermittent fasting can be easier to follow for many who have been frustrated by conventional diets. While we also recommend learning about food types and quality, starting an intermittent fasting routine does not require a long learning curve. If you have questions about any of the topics discussed here, the doctors at any of our clinics in Singapore will be able to help guide you on you health journey.
1) Byrne, N., Sainsbury, A., King, N. et al. Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study. Int J Obes 42, 129–138 (2018). https://doi.org/10.1038/ijo.2017.206

2) Elizabeth F. Sutton, Robbie Beyl, Kate S. Early, William T. Cefalu, Eric Ravussin, Courtney M. Peterson, Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes, Cell Metabolism, Volume 27, Issue 6,2018, Pages 1212-1221.e3, ISSN 1550-4131,https://doi.org/10.1016/j.cmet.2018.04.010.

3) Salim I, Al Suwaidi J, Ghadban W, Alkilani H, Salam AM. Impact of religious Ramadan fasting on cardiovascular disease: a systematic review of the literature. Curr Med Res Opin. 2013 Apr;29(4):343-54. doi: 10.1185/03007995.2013.774270. Epub 2013 Feb 18. PMID: 23391328. https://pubmed.ncbi.nlm.nih.gov/23391328/

4) Mattson, M. P., Moehl, K., Ghena, N., Schmaedick, M., & Cheng, A. (2018). Intermittent metabolic switching, neuroplasticity and brain health. Nature reviews. Neuroscience, 19(2), 63–80. https://doi.org/10.1038/nrn.2017.156

5) Witte AV, Fobker M, Gellner R, Knecht S, Flöel A. Caloric restriction improves memory in elderly humans. Proc Natl Acad Sci U S A. 2009 Jan 27;106(4):1255-60. doi: 10.1073/pnas.0808587106. Epub 2009 Jan 26. PMID: 19171901; PMCID: PMC2633586. https://pubmed.ncbi.nlm.nih.gov/19171901/

6) Leclerc E, Trevizol AP, Grigolon RB, Subramaniapillai M, McIntyre RS, Brietzke E, Mansur RB. The effect of caloric restriction on working memory in healthy non-obese adults. CNS Spectr. 2020 Feb;25(1):2-8. doi: 10.1017/S1092852918001566. PMID: 30968820. https://pubmed.ncbi.nlm.nih.gov/30968820/

7) Jordan S, Tung N, Casanova-Acebes M, Chang C, Cantoni C, Zhang D, Wirtz TH, Naik S, Rose SA, Brocker CN, Gainullina A, Hornburg D, Horng S, Maier BB, Cravedi P, LeRoith D, Gonzalez FJ, Meissner F, Ochando J, Rahman A, Chipuk JE, Artyomov MN, Frenette PS, Piccio L, Berres ML, Gallagher EJ, Merad M. Dietary Intake Regulates the Circulating Inflammatory Monocyte Pool. Cell. 2019 Aug 22;178(5):1102-1114.e17. doi: 10.1016/j.cell.2019.07.050. PMID: 31442403; PMCID: PMC7357241. https://www.cell.com/cell/fulltext/S0092-8674(19)30850-5#secsectitle0070

8) Anton SD, Moehl K, Donahoo WT, Marosi K, Lee SA, Mainous AG 3rd, Leeuwenburgh C, Mattson MP. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity (Silver Spring). 2018 Feb;26(2):254-268. doi: 10.1002/oby.22065. Epub 2017 Oct 31. PMID: 29086496; PMCID: PMC5783752. https://pubmed.ncbi.nlm.nih.gov/29086496/

9) Bhanpuri, N.H., Hallberg, S.J., Williams, P.T. et al. Cardiovascular disease risk factor responses to a type 2 diabetes care model including nutritional ketosis induced by sustained carbohydrate restriction at 1 year: an open label, non-randomized, controlled study. Cardiovasc Diabetol 17, 56 (2018). https://doi.org/10.1186/s12933-018-0698-8

Estrogen Dominant Body Type


In this shape and body type a person can experience one or many of the following symptoms or conditions:

– Pear shaped body
– Moodiness and irritability- especially during menstrual cycle
– Infertility
– Lack of libido
– Vaginal dryness
– Constipation
– Craving chocolate or creamy foods
– Depression related to menstrual cycle

Thyroid and Dysfunctional Body Type


In this shape and body type a person can experience one or many of the following symptoms or conditions:

– Fatigue
– Depression
– Anxiety
– Craving bread, pasta and sugar
– Loss of libido
– Dry skin
– Hair thinning and loss of eye brows
– Cold intolerance
– Loss of menstrual cycle
– Difficulty making decisions

Liver Overload Type


In this shape and body type a person can experience one or many of the following symptoms or conditions:

– Pot belly
– Tired and grumpy especially in the mornings
– Craving of fried and fatty foods
– Craving alcohol
– Bad breath
– Large slit down centre of the tongue
– Joint problems
– Ankle swelling
– Spider or varicose veins
– Chemical sensitivities

Stress Response Overload or Adrenal Type


In this shape and body type a person can experience one or many of the following symptoms or conditions:

– Anxiety
– Prolonged chronic stress
– Trouble getting to sleep and staying asleep
– Craving for salty foods and chocolates
– Memory and concentration issues
– Have trouble staying awake in the afternoon.