Intermittent Fasting – Yay or Nay?

Author : Anushree Kailash , INFS scholar 

Edited by : Subia Khan , Corporate consultant @ SQUATS 

Let’s understand what Intermittent Fasting is:

Intermittent fasting is not a type of diet but a diet strategy or eating pattern which times the total daily food intake into a specific number of contiguous hours to produce an extended fasting phase; as long as 24 hours. For example, one might choose to time all their meals within an 8 hour window every day. For the remaining 16 hours, they would have only water, black coffee or tea (items with no calorific value). Hence, this would result in an intermittent fast of 16 hours every day.

Intermittent Fasting does not specify calorie count or macro split. Hence it is not a diet per se. It is a time bound strategy people use for various health and convenience benefits.

The most popular variants of intermittent fasting being:

  • 16 : 8 fast (A fasting window of 16 hours including sleep hours followed by an eating window of 8 hours every day).
  • Eat – stop – eat or 5 : 2 fast (Out of seven days, complete 2 days are fasted while other 5 are with  normally timed meals). Generally the two fasted days are kept in between of the 5 days to avoid low energy levels.


To certain extent, each of us unconsciously does intermittent fasting on account of our 7-8 hour sleep which eventually results in an 8-9 hours fast.

Science behind Intermittent Fasting

Whether we are fasting or in fed state, our body needs to maintain the required blood glucose levels in order to perform its standard functions. However after several hours of fasting, the body leaves the fed state and enters a fasted state.

Depending on the physical activity level of an individual, a 12 to 24 hours fasting more often results in drop of serum glucose level and depletion of the hepatic glycogen (the glycogen stored in liver to provide energy in case serum glucose falls short) by 20% or more. There is then a switch of metabolic mode where in non-hepatic glucose, ketone bodies and free fatty acids are used as energy sources.

Different hormones assist the metabolic processes (Anabolism and Catabolism) that either cause breakdown of any tissue (fat, muscle, bone etc.) or its growth. For example; anabolic hormone like Insulin aids fat storage as well as muscle growth while Glucagon triggers fat and muscle breakdown (Yes, they work opposite of each other!). With intake of food, levels of insulin rise in the body while that of Glucagon decreases. However in case of fasted state, Glucagon increases and Insulin decreases which causes breakdown of fat to provide the required energy (ATP). This fueling further change if fasting is continued for more than 2-3 days. However it is not relevant to intermittent fasting where the fasting window is usually upto to 24 hours. Hence crux of the matter being that we do lose fat while fasting as we use fat stores as energy when food intake is stopped and glycogen is depleted. But at the same time our body is smart enough to store any excess energy as fat and replenish fat stores during that eating window. Hence it is explicit that there is no real contest to the fact that energy equations be the leader no matter which dieting strategy we use (The basic fundamental to loose being calorie deficit, to gain being calorie surplus).

It can be safely concluded that during intermittent fasting / a prolonged fasted window the catabolic process is initiated which causes fat breakdown for providing energy along with hormonal fluctuations in response but our body is an extremely smart system with lots of counterbalances and adaptations, which knows after 16 hours another 8 will come and they are not the same.

Then who is it for?

While anyone can use this strategy, most people use it for the following reasons;

  • Being on a caloric deficit diet (trying to lose fat) people generally find bigger meals more satiating then smaller and frequent meals.
  • Certain times are inconvenient to eat. E.g. Some people do not feel like eating in the morning or while they are at work.
  • Some people believe there will be hormonal benefits which is good for their fitness goal (fat loss, blood sugar regulation). While it has been researched a lot on hormonal benefits of IF but these claims are not conclusive for human body in totality.
  • Bringing in discipline at diet; IF inculcates strict timings which helps avoidance of any extra calories.  


The fasting and eating window should be selected according to the lifestyle one follows so that it is convenient and sustainable. The factors to consider for this are:

  • Training intensity and timing.
  • Routine social activities
  • Personal preferences.

Who should avoid it?

While IF sets in a disciplined and time based eating patter, some people often reward themselves with a binge after a long fasting window or else they find it inconvenient to consume the required food within a short eating window. This might result in delaying their fitness goals.

While the normal population who are well prepared to practice IF can surely pick it as their diet strategy, following set of people should avoid it without proper medical consultation and monitoring:

  • Pregnant women & Breastfeeding women
  • Underweight persons
  • Children
  • Person with any medical condition which is currently under treatment.

The check points to practicing IF

  1. Adequate water intake: Stay hydrated!
  2. Respect your bodily cues: Sleep quality, immunity, energy levels and hormonal changes vary with IF. Listen to your body!
  3. Exercise and fasting: Intense exercise during the fasting window or exercising immediately after a large meal in the eating window might be troublesome. With IF, timing for workout and meals is a real deal and should be handled thoughtfully for an overall benefit.
  4. Nutrient dense diet is still required: Intermittent fasting does not give the liberty of having empty calories during the eating window. Our body cannot perform at its best without required micronutrients (vitamins, minerals) and essential macronutrients (fats, proteins while carbs being a personal choice!).
  5. Managing hunger pangs: Body secretes hunger hormones according to the timing we are used to (Circadian rhythm). Hence, it is natural to feel hunger pangs when we increase our fasting window. Zero calorie beverages like water, black coffee or black tea / green tea, diet coke (No sugar / cream etc.) can help us tide over these hunger pangs. Coffee has been proven useful for suppressing appetite.


There are many claimed benefits of IF; however its better to stay educated on these claims being applicable to human body or not. Studies are often conducted on a group of people that share some attributes like gender, age group, body composition and medical conditions. More often initial claims for any studies are made with research being conducted on animals. Therefore before believing in such claims, we need to find out whether these conclusions hold true for us and if they are applicable.

We will be addressing these concerns with part 2 of this article “Intermittent Fasting: Vetting popular claims”.

Watch this space for more!

Happy Reading!


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