Fat to Fit – A journal of my fitness journey – Team-BHP

Fat to Fit – A journal of my fitness journey  Team-BHP

Intermittent Fasting 101

When we think of diet (low fat, low carb, keto, Atkinson’s and so on), it is always about what food to eat and what food to avoid.

Intermittent fasting is not a diet, but an eating pattern. It tells you when to eat and when not to. Two major benefits of intermittent fasting are autophagy and weight loss.

I have been using intermittent fasting as a lifestyle the past two years. Intermittent fasting is one of the important tools that helped me in my fitness journey from a 90+ kilo fat to 68 kilo fit person.

Many of my friends have used intermittent fasting as a lifestyle in healthy weight loss and 4 of them have reversed diabetes. I will write about reversing diabetes using IF in a future post.

In this post, I will discuss about intermittent fasting basics, how it works, the types of intermittent fasting and some common doubts on intermittent fasting.

Intermittent fasting is also called “IF” in short. I will be using both these terms in this post.


Before we get into the details of IF, let us look at an important hormone, Insulin which is secreted by the pancreas. We all know about its role in regulating glucose levels in the blood. Insulin signals the cells to use glucose circulating in the blood as source of energy. Insulin is also a storage hormone. It signals fat cells to convert glucose circulating in blood into fat and store it for later use.

In the presence of insulin, body does not burn fat. But burning fat is the key to weight loss. To make the body burn fat, we need to achieve zero insulin levels for extended periods of time. Low carb diets like Paleo, Keto and Atkinsons achieve this by limiting carbs which in turn reduces blood glucose levels which in turn keeps insulin levels very low, thus enabling the body to burn the stored fat for fuel. Workouts can achieve this by burning glucose for energy and bringing down insulin levels.

Intermittent fasting achieves this by extending the fasting period (when you do not eat any food).

How Intermittent Fasting Works:

It takes about 12 hours after a carb loaded meal for insulin levels to reach zero (with low carb meals, this happens much sooner). Fat burn can occur only after these 12 hours. But in today’s lifestyle of abundance of food, we start eating right from the time we get out of bed and all the day till we go to bed – coffee, breakfast, pre-lunch snack, lunch, post lunch snack with coffee and dinner. We usually get only 8 to 10 hours of time window when we are not eating. Because of this we never allow insulin levels to reach zero.

In intermittent fasting we extend this “not eating” time window beyond 12 hours so that body can start burning fat for fuel after insulin levels become zero.

Types of Intermittent Fasting:

There are two windows in intermittent fasting – eating window and fasting window. Eating window is when you have your meals and fasting window is when you do not eat anything. Depending on the duration of fasting and eating windows, following are some of the famous IF protocols.

16:8 – 16 hours of fasting window and 8 hours of eating window
18:6 – 18 hours of fasting window and 6 hours of eating window
20:4 – 20 hours of fasting window and 4 hours of eating window
OMAD (One Meal A Day) – In this method you fast for 23 hours and eat a single meal within a time window of an hour.

How to Start:

There are two ways to start intermittent fasting.

In the first method, you start with a 13-hour fasting window. Have an early dinner by 7pm and have your first meal of the day at 8am. Eat nothing between 7pm and 8am. Do this for a few days and then increase the window to 14 hours pushing your first meal to 9am. Keep increasing it till you get to the 16-hour window.

In the second method, you start with a 16-hour window from day 1. Have your last meal of the day at say 8pm and the first meal of the day at 12 noon the next day. This method gets you into IF faster and you will start seeing results sooner. I used this method when I started my IF lifestyle. You may experience symptoms like severe hunger pangs or mild headaches in this method. This is your body resisting the switch over to burning fat as fuel. But this lasts only for two to three days. Once you tell your body you are not giving it any food, the body automatically starts breaking up the stored fat for energy. And when this happens you will start feeling much more energetic in fasted state than you were when you had your early meal.


The most important benefit of IF is autophagy. I consider this as the main advantage with weight loss as the beneficial side effect.
In 2016, the Nobel Prize for Physiology was awarded to Dr. Yoshinori Ohsumi for his research on autophagy.

“Auto” means self and “Phagy” means eating. Autophagy literally means self-eating – in a good way. We know cells keep dividing in our body and new cells are created from this division. After several divisions, cells become dysfunctional and cannot be used for further division. Autophagy is body’s way of cleaning up these damaged cells and recycling them for energy – or self-eat. Autophagy is part of our evolution process to clean our body of debris and to extend life. It is body’s own way of housekeeping.

However, Autophagy gets activated only in fasted state. When we are constantly in the fed state, body is busy processing the food that we have put in that it does not get time for housekeeping. Intermittent fasting, with its extended fasting hours activates this process. Autophagy gets active only after 18 to 20 hours of fasted state. So, to get the benefits of autophagy, we need extended fasts. I do an extended fasting of 36 hours or 48 hours once a month and 20+ hours of fasting once or twice a week.

By getting rid of all the defective cells and debris, Autophagy essentially slows down or sometimes even reverses the aging process. In my own experience, when I started IF, my friends started telling me I was looking younger. That is the power of IF. As a reference below is a comparison. The left image is me when I was 38 years old. The right one is me at 48 years.

IF and Workouts:

As I have mentioned in the previous posts, if the goal is to lose weight, diet is the key. So, if you practice IF without any physical activity, you will still lose weight in a healthy way.

However, adding workouts to IF gives you a double advantage of getting healthy and fit. Also, when you workout in the fasted state, you will aid the body to use up all the stored glycogen (glucose stored in muscles and liver) faster and switch to fat burning till the next meal.

Do 30 to 45 minutes of brisk activity in fasted state. This could be a brisk walk, jog, cycling, swimming, badminton or any other similar activity. The goal should be to perform this activity 12 hours after the last meal just when insulin levels hit zero. And extend fasting for a few hours after the activity.

Another useful workout to go with IF is HIIT (High Intensity Interval Training). In this method, you perform at high intensity for 30 seconds to a minute and then recover a couple of minutes and repeat. HIIT due to the high intensity efforts uses up the glycogen stores faster and helps in quicker weight loss.

Which IF method to follow:

This greatly depends on your current health and weight and your goals. If you have a lot of body weight to lose, then longer fasts like 20:4 or OMAD will be beneficial. If you are not too overweight and want to maintain your weight, then 16:8 with a few longer fasts will help.

I recommend mixing it up and keep the body from settling into a routine – after all that is what our body has been designed for.

Personally, I have made 16:8 as my standard with an hour’s workout 5 days a week. I do 20+ hours of fasting on my recovery and rest days. I do an extended fasting of 36 or 48 hours once a month.

Common Doubts on IF:

Below are some of the common doubts that come to everyone’s mind when considering IF.

Breakfast is the most important meal of the day and you are asking me to skip breakfast:

We have grown up with everyone from our parents to Kelloggs telling us breakfast is the most important meal of the day.

In the million+ years of human evolution, the concept of timed meals appeared only in the civilized society. In the paleolithic age of hunter gatherers there was no concept of breakfast, lunch and dinner. Human beings used to hunt for food and till the next hunt go without food. There is a reason why our body developed the fat storage mechanism. This is to store fat during abundance and burn fat when there was no food. This is what helped humans to survive. But in our present lifestyle, we only activate the fat storage part and never let the body to use the stored fat.

With the extended fasting hours, we are activating the mechanism that our body has evolved over a million years. Also, technically, the first meal you have after a fast is the breakfast. There is no need to have it at 8 in the morning.

Will I get acidity:

Another question most of my friends ask me is will they get acidity with IF. Body is an intelligent machine. As we have trained it with breakfast at 8 am day after day, it gets into a routine and even before you put food in your mouth, it can start the preparing for digestion by secreting acid in the stomach. Once the body sees that food is not arriving at this expected time, it takes just three to four days for it to reprogram this schedule.

What is allowed during the fasting window:

This is an important doubt everyone beginning IF has. What can I have during my fasting window? Anything that has zero calories (I definitely do not recommend Coke Zero) – green tea, black coffee (without cream or sugar), or just plain water. In longer fasts, you may consider having a glass of lime juice with salt to compensate for electrolytes.

What should be the eating window:

There is no rule for this. You can choose your eating window based on your lifestyle and preference. For example, in a 16:8 fast, you could skip your morning meal and set your eating window between 12 noon to 8pm, or skip your evening meal and set your eating window between 8am to 4pm.

Who can do IF:

Fasting is not recommended for pregnant ladies, kids below 18 years and for people who are underweight. Everyone else can follow IF.


After experimenting with various techniques like calorie counting, low carb, Keto and IF, I find IF to be the most sustainable lifestyle change for a healthy life and to maintain a healthy weight.

Last edited by graaja : 20th November 2020 at 23:04.