Intermittent Fasting

Oct 20, 2020 | Teacher's Corner

Intermittent fasting is a pattern of eating in which you have two ‘eating’ periods during a day: one during which you eat and one during which you don’t (thus fast). It is a lifestyle pattern rather than a diet, which focusses on when you eat rather than what you eat.


There are a number of ways of fasting intermittently, with the following two being among the most popular and manageable for most people:

The 16/8 method

Here you fast for 14 to 16 hours and only eat during the ‘remaining’ 10–8-hour window. During this eating period, you can eat two meals as well as some snacks. However, while you may eat ‘anything’ during the eating window, you should still be sensible: so restrict high-calorie or junk food.  During the fasting period you may drink water and coffee and tea (no milk). This may sound drastic, but all it actually means is that you skip breakfast!

The 5:2 diet

Here you eat normally (again within reason) five days of the week and restrict your calorie intake to 500 (women) and 600 (men) two days of the week. The two days don’t have to be consecutive, so you could the two that suits you best. 

Other forms of intermittent fasting include Eat Stop Eat (a 24-hour fast one or two days per week, from dinner one day to dinner the next day); Alternate-day Fasting (so you fast every second day); the Warrior Diet (eating small amounts of raw fruits and vegetables during the day and a large meal in the evening – also known as OMAY or One Meal a Day); and Spontaneous Meal Skipping (spontaneously skipping meals when you are not hungry or too busy to eat). (Kirs Gunnars, 6 popular ways to do intermittent fasting, Healthline, 1 January 2020, (accessed 28 July 2020).)

All these methods do work, but they are in my opinion either too difficult (going hungry to bed doesn’t appeal to me) or too unstructured (did I fast two days ago? not going to do it today – let’s see how it goes tomorrow).

The health benefits of intermittent fasting

Intermittent fasting has become generally accepted, although it seems totally contrary to what we were taught in the past (you’ll faint at school or work and be unable to concentrate if you don’t eat a healthy breakfast). However, there are numerous claims that it results in weight loss and improved metabolic health, and a number of studies that provide evidence of its health benefits:

It can help you lose weight and belly fat: Obviously, you eat fewer meals, so unless you compensate by eating much more during the eating window, you will consume fewer calories. When you enter into the state of fasting (about 8–10 hours after your last meal), your body would have burned through the glucose stored in your liver, and begins to break down and use fat to get energy (this is known as ‘metabolic switching’). And for many of us, the most fat accumulates around the liver and other organs, resulting in that ‘spare tyre’. During this process it changes hormone levels to make stored body fat more accessible.

It enhances hormone function:
During fasting you have lower insulin levels, higher growth hormone levels and increased amounts of norepinephrine (noradrenaline), which all increase the breakdown of body fat and facilitate its use for energy. By increasing your metabolic rate, it helps you burn even more calories.

Intermittent fasting changes the function of cells, genes and hormones:
During the fasting process your body initiates cellular repair processes, such as removing waste material from cells. This happens because fasting triggers a metabolic pathway called autophagy, which removes waste material from cells. (Kirs Gunnars, 10 Evidence-Based Health Benefits of Intermittent Fasting, Healthline, 16 August 2016, (accessed 24 July 2020.)

Other health benefits:
A WebMD paper summarises the current scientific evidence, with studies showing that intermittent fasting can stabilise blood sugar levels, increase resistance to stress, and suppress inflammation. It can also decrease blood pressure and cholesterol levels, and improve one’s resting heart rate. (Thompson, D, Improve brain health and memory. ‘Intermittent Fasting’ Diet Could Boost Your Health, HealthDay News, 26 December 2019 (accessed 1 August 2020).)

Reduction of insulin resistance:
This is good news for persons at risk for type 2 diabetes, for by helping to lower blood sugar levels, intermittent fasting reduces insulin resistance. (Adrienne R.Barnosky, Kristin K.Hoddy, Terry G.Unterman & Krista A.Varady, Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings, (accessed 28 July 2020).)

Improved brain functioning:
Studies (albeit mostly on animals such as rats at this stage), also suggest that there could be benefits for one’s brain, because intermittent fasting could reduce oxidative stress and inflammation and increase levels of a brain hormone called brain-derived neurotrophic factor. A deficiency of this hormone has been implicated in amongst others depression. It may also delay the onset of Alzheimer’s disease or reduce its severity (J Lee, et al., Dietary restriction increases the number of newly generated neural cells, and induces BDNF expression, in the dentate gyrus of rats, National Library of Medicine, (accessed 31 July 2020); Halagappa, VKM, et al., Intermittent fasting and caloric restriction ameliorate age-related behavioral deficits in the triple-transgenic mouse model of Alzheimer’s disease, 26 April 2007, National Library of Medicine, National Library of Medicine,(accessed 23 July 2020.)

The do’s and don’ts of intermittent fasting


  • Do consult a doctor before you start if you suffer from an underlying health condition such as type 2 diabetes, low blood sugar or an eating disorder.
  • Do listen to your body. Start small and if you start to feel lethargic or any negative effects, do eat something.
  • Do stop if you’re exercising and start to feel lightheaded, dizzy or very tired.
  • Do follow some dietary rules:
    • Don’t drink any artificially sweetened beverage or zero-calorie cool drinks.
    • Fasting doesn’t give you a licence to eat anything you want. You will still have to make healthy and smart food choices.
    • Eat a low carbohydrate diet.
    • Eat foods with a high fibre content (these are more filling) and pair it with foods higher in healthy fats.
    • Limit high-calorie foods. If you eat more than your recommended daily allowance, you will still gain weight.
    • Your first meal after fasting should preferably contain protein, vegetables and a complex carbohydrate



  • Don’t restrict calories during the eating period: You need to give your body energy so that it can function properly.
  • Don’t binge-eat during the eating period: The opposite of restricting calories is binging, which can also be detrimental because you will increase calorie consumption and slow down the benefits of fasting altogether.
  • Don’t undertake high-intensity exercise during the fasting period: Stick to your normal workout routine, and don’t work to the point of exhaustion. If your body requires more energy that it is able to draw from your fat cells, you will start to burn muscle for energy. (Jones, I, The dos and don’ts of intermittent fasting, posted 18 October 2019, accessed 2 August 2020; Sheroes, All about intermittent fasting: food, benefits dos & don’ts, 4 June 2018, accessed 2 August 2020

Intermittent fasting can be a great way to not only lose weight, but keep the weight down permanently, but only if you approach it sensibly, and follow basic guidelines.

(Marielienne Janeke)