Intermittent Fasting 101: Beginner’s Guide

Intermittent fasting is currently one of the world’s most popular health and diet trends for its promises of improved health, sleep and weight control. Many diets focus on what to eat, but intermittent fasting is all about when you eat. Intermittent fasting is an eating pattern that cycles between periods of fasting and eating. In fact, you may have already done many intermittent fasts in your life. There are several forms of intermittent fasting:

  • Alternate day fasting, as the name implies, this diet involves fasting every other day.
  • Modified alternate day fasting, which requires you to only eat 25% of your usual intake every other day
  • Periodic fasting, which requires you to full fast for 24 hours or limit food to about 500-600 calories a day on only two days per week e.g. eat-stop-eat diet, the 5:2 method
  • Time restricted eating, which limits your daily eating window e.g. the 14:10 diet, the 16:8 diet
  • The warrior diet, which requires you to undereat for 20 hours per day, then feasting on one huge meal at night within a 4-hour overeating window

When you fast, several things happen in your body on the cellular and molecular level. Advocates claim that extended fasting periods increase levels of human growth hormone, improve insulin sensitivity, promote cells to repair as well as alter gene expression related to longevity and protection against diseases. These suggested that intermittent fasting can have powerful benefits for obesity, diabetes, cancer and many other chronic diseases. It may even help you to live longer.

However, intermittent fasting isn’t for anyone. Some plans may cause more side effects than others. Side effects include muscle mass loss, headache, nausea, anxiety, etc. Besides that, it can be dangerous if you on medication or having medical conditions. Therefore, it is important to check in and discuss with your nutritionist/ primary care practitioner first before choosing a plan that works with your lifestyle. This is particularly important if you:

  • are under 18 years old.
  • are underweight.
  • are a woman who is trying to conceive.
  • are pregnant or breastfeeding.
  • are taking medications.
  • have diabetes.
  • have low blood pressure.
  • have a history of eating disorders.
  • have any other medical conditions.

If you are not in any of these categories, you can try experiment with the different approaches and find something that you enjoy and fits your schedule. Keep in mind that you should:

Best is to plan all your meals and snacks at least a day in advance. Intermittent fasting may make you feel sick, your brain may not perform as well as you are used to. This may only be temporary, as it can take some time for your body to adapt to the new meal schedule. If symptoms persist, you should consult your nutritionist/ physician right away.


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  • Ho, K. Y., Veldhuis, J. D., Johnson, M. L., Furlanetto, R., Evans, W. S., Alberti, K. G., & Thorner, M. O. (1988). Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man. The Journal of clinical investigation81(4), 968–975.
  • Kim I, Lemasters JJ. Mitochondrial degradation by autophagy (mitophagy) in GFP-LC3 transgenic hepatocytes during nutrient deprivation. Am J Physiol Cell Physiol. 2011 Feb;300(2):C308-17. doi: 10.1152/ajpcell.00056.2010. Epub 2010 Nov 24. PMID: 21106691; PMCID: PMC3043636.
  • Zhu Y, Yan Y, Gius DR, Vassilopoulos A. Metabolic regulation of Sirtuins upon fasting and the implication for cancer. Curr Opin Oncol. 2013 Nov;25(6):630-6. doi: 10.1097/01.cco.0000432527.49984.a3. PMID: 24048020; PMCID: PMC5525320.

Jacie Chiew

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