Remember when we were told breakfast was the most important meal of the day?
“Eat breakfast like a King, lunch like a Prince, and dinner like a Pauper”
What about eating every four, three, or even two hours?
“Eat smaller, more frequent meals to increase your metabolism and prevent weight gain”
Patterned eating is a controversial topic. And, just like almost everything related to nutrition, the research is sporadic, patchy, and disconnected; some nutrition experts are advocating one thing while others are advocating the complete opposite.
There is one method of patterned eating (or lack of), however, that has gained a significant amount of momentum over the past few years.
By definition, Intermittent Fasting (IF) is an eating pattern that cycles between brief periods of fasting, with either no food or significant calorie reduction, and periods of ‘unrestricted’ eating. (1) Unlike ‘conventional diets’, IF does not specify which foods you should eat. Instead, IF protocols specify when foods should be eaten and, conversely, when they should not be. And, unlike ‘conventional diets’, IF has been practiced since earliest antiquity. (2) In religious cultures, for example, fasting was and still is in some cases, associated with patience and other forms of self-control.
Recently, however, the fundamental reasons for fasting has drifted from the passages of their religious imports and entered the aisles of the health and wellness industry.
Intermittent Fasting and Health Benefits:
IF regimes have shown to influence a range of physiological mechanisms within the body and have proven to generate positive health outcomes in individuals.
Some of the health benefits of IF include:
- Weight Loss
And rightly so considering the fundamentals of IF is to restrict your window of eating, reduce the number of meals consumed and in turn consume fewer kilojoules.
- Improve Brain Function
IF may play a role in reducing brain-cell degeneration and improving, or at least maintaining, optimal brain function (3 – 5)
- Regulate Blood Sugar Levels
IF may play a role in improving insulin sensitivity, an important risk factor for type 2 diabetes. (6) On top of this, IF has shown to help reduce visceral abdominal fat, fasting insulin, and insulin resistance. (7, 8). These are all factors which predispose individuals to diabetes.
- Maintain a Healthy Heart
Some fasting protocols have demonstrated a positive reduction in total cholesterol, triglycerol, LDL cholesterol, and systolic blood pressure; all biomarkers of heart disease. (9 – 12)
- Improve Gut Health
The gut microbiome is highly dynamic, exhibiting daily cyclical fluctuations. (13) Time-restricted feeding have shown to contribute to diversity of the gut microbiome and lead to reduced gut permeability and blunted inflammation. (14 – 16)
Tempted yet? Not so fast.
Although there is a plethora of anecdotal evidence from human studies and (borderline) significant effects from animal studies, the mechanisms (and hence the reasons) behind why fasting can produce such benefits in humans is still unknown. On top of this, and regardless of whether the benefits are experimentally significant or not, due to the nature of IF, it should always be approached with caution…
Side Effects of IF include:
- Low energy
- Heartburn, bloating and constipation
- Feeling cold
- Overeating within the ‘eating window’
Precautions of Intermittent Fasting:
There are also some people who should avoid fasting altogether:
- Pregnant and Breastfeeding Women or trying to get pregnant
- History of an Eating Disorder or Amenorrhea (lack of menstruation)
- Low blood pressure
- Nutritional deficiencies
- Gut issues, Food Sensitivities
- Chronic Anxiety/Stress
- Sleep Problems
Hungry to Know How to ‘Fast’?
Although IF seems fairly straight forward (eat, fast, eat, repeat?), there are different approaches used to split the day or week into fasting and non-fasting periods.
As the name suggests, this method of fasting involves restricting the time you spend eating each day. The most common approach is by restricting your ‘eating window’ to eight hours. The remaining 14 hours of your day involves ‘fasting’ where you can drink water, black coffee, other non-caloric beverages. The eating window, however, can be shortened to six hours (or less) depending on the individual.
Although the fasting window may seem overwhelming, if you schedule it right it could be as simple as not eating anything after dinner and then skipping breakfast. Easy done!
Modified Fasting Regimens (5:2 Diet Plan)
This plan involves the consumption of 20-25% of energy needs on regularly scheduled ‘fasting’ days. This regime is the basis for the popular 5:2 diet, which involves energy restriction for 2-non-consective days a week and usual eating the other 5 days.
Complete Alternate Day Fasting:
Possibly one of the hardest methods to commit to, complete alternate day fasting involves doing a 24-hour fast, once or twice a week. In other words, one to two days a week, you eat absolutely nothing.
Food (or lack of) for Thought:
It is important to emphasise that IF is not a ‘fad’, nor is it an excuse to bypass nutrient-dense foods (or food altogether). While fasting may be great for some people, keep in mind that the way you ‘break the fast’ is just as important. It’s counterproductive and potentially dangerous to fast and then immediately binge on unhealthy foods. Instead, try incorporating foods which contain plenty of protein, fibre, vegetables, and health fats.
Now, who’s hungry!
- School of Public Health. Diet Review: Intermittent Fasting for Weight Loss [Internet]. 2018 [ctied 2018 December 19]. Available from: https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/intermittent-fasting/
- Brongers E.H. Instruction and Interpretation: Studies in Hebrew Language, Palestinian Archaeology and Biblical Exegesis. Brill Academic Pub; 1997.
- Bathina S, Undurti N.D. Brain-derived neurotrophic factor and its clinical implications. Arch Med Sci [Internet]. 2015 Dec 10 [cited 2018 Dec 22];11(6):1164-78. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4697050/
- Lee J, Duan W, Long JM, Ingram DK, Mattson MP. Dietary restriction increases the number of newly generated neural cells, and induces BDNF expression, in dentate gyrus of rats. J Mol Neurosci [Internet]. 2000 Oct [cited 2018 Dec 22];15(2):99-108. Available from: https://www.ncbi.nlm.nih.gov/pubmed/11220789
- Lee J, Seroogy K, Mattson M. Dietary restriction enhances neurotrophic expression and neurogenesis in the hippocampus of adult mice. J Neurochem [Internet]. 2002 Jan 21 [cited 2018 Dec 22]; 80(3):539-47. Available from: https://onlinelibrary.wiley.com/doi/full/10.1046/j.0022-3042.2001.00747.x
- Varady K, Hellerstein M. Alternate-day fasting and chronic disease prevention: a review of human and animal trials. Am J Clin Nutr [Internet]. 2007 July 1 [cited 2018 Dec 22];86(1):7-13. Available from: https://academic.oup.com/ajcn/article/86/1/7/4633143
- Barnosky A, Kristin H, Unterman T, Varady K. Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human finding. Translation Research [Internet]. 2014 Oct [cited 2018 Dec 22];164(4):302-311. Available from: https://www.sciencedirect.com/science/article/pii/S193152441400200X
- De Azevedo F, Ikeoka D, Caramelli B. Effects of intermittent fasting on metabolism in men. J Brazilian Med Assoc [Internet]. 2013 Apr [cited 2018 Dec 22];59(2):167-173. Available from: https://www.sciencedirect.com/science/article/pii/S0104423013000213
- Varady KA, Bhutani S, Church EC, Klempel MC. Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults. Am J Clin Nutr [Internet]. 2009 Nov [cited 2019 Jan 2];90(5):1138-43. Available from: https://www.ncbi.nlm.nih.gov/pubmed/19793855
- Heilbronn LK, Smith SR, Martin CK, Anton SD, Ravussin E. Alternate-day fasting in nonobese subjects: effects on body weight, body composition and energy metabolism. Am J Clin Nutr [Internet]. 2005 Jan [cited 2019 Jan 2];81(1):69-73. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15640462
- Antoni R, Johnston K, Collins A, Robertson D. The effects of intermittent energy restriction on indices of cardiometabolic health. Research of Endocrin [Internet]. 2014 Jun 28 [cited 2019 Jan 2];2014. Available from: https://ibimapublishing.com/articles/ENDO/2014/459119/
- De Azevdeo F, Ikeoka D, Caramelli B. Effects of Intermittent fasting on metabolism in me. Brasileira [Internet]. 2013 Mar [cited 2019 Jan 2];59(2):167-73. Available from: https://www.sciencedirect.com/science/article/pii/S0104423013000213
- Zarrinpar A, Chaix A, Yooseph S, Panda S. Diet and feeding pattern affect the diurnal dynamic of the gut microbiome. Cell Metab [Internet]. 2014 Dec 2 [cited 2018 Dec 22];20(6):1006-17. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25470548
- Laugerette F, Alligier M, Bastard JP, Drai J, Chanseaume E, Lambert-Porcheron S, Laville M, Morio B, Vidal D, Michalski MC. Overfeeding increases postprandial endotoxemia in men: inflammatory outcomes may depend on LPS transporters LBP and sCD14. Mol Nutr Food Res [Interet]. 2014 Jul [cited 2019 Jan 4];58(7):1513-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/24687809
- Shen J, Obin MS, Zhao L. The gut microbiota, obesity and insulin resistance. Mol Aspects Med [Internet]. 2013 Feb [cited 2019 Jan 4];34(1):39-58. Available from: https://www.ncbi.nlm.nih.gov/pubmed/23159341
- Tilg H, Kaser A. Gut microbiome, obesity, and metabolic dysfunction. J Clin Invest [Internet]. 2011 Jun 1 [cited 2019 Jan 4];121(6):2126-2132. Available from: https://www.jci.org/articles/view/58109
Alice Bleathman is a passionate nutritionalist with special interests in gastrointestinal health, sports dietetics, and women’s health. As an upcoming dietetics student at Deakin University, Alice aims to inspire individuals to improve their health through wholesome, simple and personalised nutrition programs. As a former writer for the Nutrition Press and Ideal Nutrition, Alice appreciates the power of the internet in educating people on improving their health and wellbeing. As a writer of liliaconvit. com, Alice imparts her thorough and analytical understanding of nutrition concepts to encourage learning about all facets of health and nutrition.