Intermittent Fasting: What is it?

Approved by Consultant Nutritionist, Malavika Athavale.

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Intermittent Fasting (IF) is essentially an on and off cycle of fasting and eating that claims numerous benefits, including weight loss, preventing weight gain, lowering blood pressure, increasing insulin sensitivity, improved cardiovascular health, extended lifespan and increased resistance to age-related diseases. It is said to do so through both, reduced frequency of meals and caloric restriction. ​1–3​

Click here to see the conditions where Intermittent Fasting can help.

Intermittent fasting is about when you should eat, and not about what you’re eating. This means it is possible to maintain different types of diets while simultaneously also following an intermittent fasting protocol.

Different types of intermittent fasting methods exist, which are about dividing eating and fasting through the course of a day or the duration of a week. Here are two of the better known ones:​4​

  1. Sixteen by Eight [16/8]: In this method, we fast for 16 hours and can eat anytime during the remaining 8 hours. For example, finish dinner by 8pm and then eat your next meal at 12pm the next day. Your 16 hour fasting window can be modified to suit your preferences and schedule.
  2. Five by Two [5/2]: This method involves fasting for 2 days of the week and eating during the remaining 5. You can eat 500 – 600 calories during your fasting period.

Personally, I try and do four 16/8 fasts a week, followed by a 24 hour fast, and then take a break on the weekend.

Eating during 16/8 intermittent fasting isn’t allowed, though we can drink a few liquids, mentioned below. None of the beverages mentioned below should have sweeteners, whiteners, milk, sugar or other flavours. We can also have nutritional supplements, as long as they do not have any calories. Avoid those cod liver oil capsules and similar supplements during your fasting period. If in doubt, check the nutrition label on the product. You may need to take some of your regular medications during your fasting window and most of these are fine. Consult your doctor if you’re in doubt.

  1. Black coffee
  2. Black or green tea
  3. Club soda
  4. Water

Frequently Asked Questions about Intermittent Fasting

What should I break my fast with? Anything you like. I tend to feel heavy and sluggish if I break my fast with big and/or carb heavy meal. After a few fasts, you’ll come up with your own fast-breaking routine.

What should be my last meal before a fast? Again, anything you like. It depends on how your body reacts to which foods. I prefer eating a meal of vegetables, lentils, legumes and protein just before beginning a fast, as I think it lasts longer and doesn’t cause hunger pangs for longer than if I include rotis or rice in the meal. After a few trials and fasts, you’ll figure out what works best for you.

What can I eat during my eating window? Eat meals during your eating window that are normal for you. For example, if you’re diabetic, you may want to lay off the carbs during your eating window.

Do I need nutritional supplements? This depends on how much nutrition you can pack into your eating window. Considering we’re eating less frequently, it is possible we may not complete our RDAs of required nutrients. Speak to your doctor or nutritionist and understand what you require, and how to obtain it from dietary sources, failing which, you could consider consuming supplements.

Can I exercise while fasting? Yes, you can, though there are a few considerations, such as timing, macros based workouts, eating the right food after exercising and so on. Additionally:​5​

  1. It is possible to burn more body fat
  2. Possibility of slowing down of metabolism, if you’re fasting long term
  3. Workout performance may be lower than otherwise and
  4. You may either lose or be unable to build muscle mass

Is this a one off thing or a lifestyle? That’s an individual decision that I suggest you take after you’ve experienced intermittent fasting as well as your body’s reaction to it. Speaking for myself, it’s a lifestyle and one that I plan to continue.

Can those with gallbladder conditions intermittently fast? Fasting has implications on the gallbladder and could effect related conditions such as stones. Please speak with your doctor prior to beginning fasting if you have a gallbladder condition.

Who should not consider intermittent fasting? Fasting should not be undertaken by those with hormonal imbalances, pregnant and breastfeeding women, diabetics (under qualified supervision), those with eating disorders and the underweight. ​6​

Why am I not seeing results / when will I see results? This depends on what results you’re looking for. I see improvements in blood sugar levels after a single day of fasting, and weight improvements are usually on a weekly basis. Also, fasting alone may not bring about results – it needs to be combined with healthier lifestyle and dietary choices. Finally, individual bodies respond differently.

Should I eat at the same time every day? Can I vary my fasting hours?Is it okay to count only my fasting hours since I can’t eat at same time each day? You can eat whenever you like as long as you’re maintaining a continuous 16 hour fasting window on the day of your fast. Personally, I keep things a bit random and try not to settle down into a steady schedule or rhythm, apart from ensuring I fast 4 – 5 times a week.

Is it better to eat bigger meals less frequently or smaller meals more frequently, during my eating window? How many meals can I eat in the 8 hour eating window? As long as you’re able to get enough calories (energy) and complete your daily requirements of micro-nutrients, feel free to adjust your eating patterns per your own schedule and preferences. I suggest small, frequent, nutrient dense meals, following a low carb healthy fat diet with plenty of legumes, lentils, vegetables and other plant based foods.

Can intermittent fasting be harmful otherwise? There is little evidence that intermittent fasting is harmful in healthy, normal, overweight or obese adults, mentally (moods) or physically.​7​

Do you have more questions? Ask them in the comments below and I’ll update this article with your questions and the answers.

If you need company and support during your IF journey, join my fasting circle on the LIFE app, my Facebook group – Intermittent Fasting for Health and Wellness or the Telegram group – Healthy Living, where we have a useful bot to help too.

Recommended reading: Delay, Don’t Deny: Living an Intermittent Fasting Lifestyle


  1. 1.
    Mattson M, Wan R. Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. J Nutr Biochem. 2005;16(3):129-137. https://www.ncbi.nlm.nih.gov/pubmed/15741046.
  2. 2.
    Stockman M, Thomas D, Burke J, Apovian C. Intermittent Fasting: Is the Wait Worth the Weight? Curr Obes Rep. 2018;7(2):172-185. https://www.ncbi.nlm.nih.gov/pubmed/29700718.
  3. 3.
    Mattson M, Longo V, Harvie M. Impact of intermittent fasting on health and disease processes. Ageing Res Rev. 2017;39:46-58. https://www.ncbi.nlm.nih.gov/pubmed/27810402.
  4. 4.
    Gunnars K. What is Intermittent Fasting? HealthLine. https://www.healthline.com/nutrition/what-is-intermittent-fasting. Published June 4, 2017.
  5. 5.
    Lindberg S. How to Exercise Safely During Intermittent Fasting. HealthLine. https://www.healthline.com/health/how-to-exercise-safely-intermittent-fasting. Published October 26, 2018.
  6. 6.
    Malinowski B, Zalewska K, Węsierska A, et al. Intermittent Fasting in Cardiovascular Disorders-An Overview. Nutrients. 2019;11(3). https://www.ncbi.nlm.nih.gov/pubmed/30897855.
  7. 7.
    Patterson R, Laughlin G, LaCroix A, et al. Intermittent Fasting and Human Metabolic Health. J Acad Nutr Diet. 2015;115(8):1203-1212. https://www.ncbi.nlm.nih.gov/pubmed/25857868.

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