42 hours fasting results

How did I end up doing it?

I am doing Intermittent Fasting for 23 weeks now. Starting from about 18th week my weight loss plateaued and I needed to do something to get it moving. So I recalled that I can try doing extended fasts which are fasts longer than 24 hours. Well, I decided to do 42 hours fast that starts on 6:00 PM and ends after 42 hours on 12:00 PM.

Initial setup

Fasting length

From 5:40 PM on Wednesday, Nov 9th to 11:59 AM on Friday, Nov 17th.

Fasting progress

Detailed progress

Same information as a graph

Final result

After 42 hours of fasting 12:00 PM

weight after 40 hours of fasting

The fast has been finished successfully. Overall feeling is good. Nothing special to report except for crumbling belly feeling yesterday in the evening.

  • Initial weight was 77.2 kg (170.2 lb). Final weight is 74.7 kg (164.7 lb). That’s after drinking a cup of water and a cup of coffee which added about 0.4 kg (0.9 lb) of weight.

Significant weight loss at the very last hours of the fast

Again the same observation

Initial setup

Weight at 14th hour of the fast just before going for a walk/running was 75.8 kg (167.1 lb), body fat 23.9 %.

After walking

After walking/running for 66 minutes on 14th hours of the fast and doing 6.67 km (4.14 mi), weight became 75.3 kg (166 lb), body fat 23.8 %.

Overall weight loss 0.5 kg (1.1 lb), body fat 0.1 %.

Now, after 5 months of measuring weight to fat loss dependency,
Speaking of myself, I know that losing 0.1 % of body fat corresponds to 100 gram (0.22 lb) of fat loss.

Net body fat loss

So net body fat loss is 100 gram (0.22 lb) and the rest of 400 gram is water (sweat, breathing) and possibly energy that went on heating the body, since I walked at 5 degrees centigrade (41 F) with only T-shirt and light jacket on.

Why Calories In equals Calories Out is wrong again

According to tracker calculation below I burned 378 calories, which is 378 / 9 calories in 1 gr of fat = 42 gram of fat loss.

Again, it contradicts what my scale is showing, which means that Calories In = Calories Out theory is wrong. But we knew this already.

Books that literary make you who you are


There are a number of posts that I wrote about books and how they helps us change our lives and ourselves. The books below literary helped me to change my body composition and shed dozens of pounds of fat that came from eating sugar, sweets, starchy foods and drinking soft drinks, in short, what we call nowadays Ultra Processed Food.

It seems to me they could be helpful to some of you who wants to make a change.

Books on fasting I read and recommend

I sorted the books based on how I liked them the most.

  1. FAST. FEAST. REPEAT by Gin Stephens
  2. The Obesity Code by Jason Fung
  3. The Complete Guide to Fasting by Jason Fung
  4. Why We Get Sick by Benjamin Bikman
  5. The Circadian Code by Satchin Panda
  6. Fat Chance by Robert Lustig
  7. The Case Against Sugar by Gary Taubes
  8. The Intermittent Fasting Revolution by Mark Mattson
  9. The Every Other Day Diet by Krista Varady
  10. Delay, Don’t Deny by Gin Stephens (it was her first book on the subject. In comparison to her second this one has more personal info about Gin’s experience with IF)

Books on nutrition that I read, but they were not that easy to make it through

  1. The Case For Keto by Gary Taubes
  2. The Big Fat Surprise by Nina Teicholz
  3. Metabolical by Robert Lustig
  4. Swallow This by Joanna Blythman (I’ve finished only 3/4 of this book. It turned to be quite boring)

Intermittent Fasting isn’t a diet

There is a difference

There is a big difference between Intermittent Fasting (Time-restricted Eating) and a diet (Calorie Restriction).

In the Flipping the Metabolic Switch: Understanding and Applying Health Benefits of Fasting (Obesity, 2018 Feb., 26(2): 254-268) paper by Mark P. Matson et al. they are defined as follows,

  • Intermittent Fasting (IF) – This eating pattern involves fasting for varying periods of time, typically for 12 hours or longer.
  • Calorie Restriction (CR) – This eating pattern involves a continuous reduction in caloric intake without malnutrition.

Your typical diet

During regular diet when caloric intake is restricted a few things happen to your body.

  1. The body tunes down your metabolism. As a consequence you can have a feeling of cold, mood change and feeling of tiredness.
  2. Due to lower Leptin hormone, which signals to the brain that you have not enough stored energy, you start feeling continuous hunger.
  3. While at first you lose some weight (mostly muscle), in the end after struggling with the diet you gain your weight back, but more. After all 99.5 % of diets fail.

As for Intermittent Fasting

While you fast for at least 16 hours, which allows your body to deplete glycogen stored in muscles and liver, your body will switch from using glucose as a main source of energy to using ketones produced by liver from fatty acids (fat).

  1. When this transition happens your body is perfectly happy, there is no feeling of hunger.
  2. Metabolism is actually elevated and you feel good.
  3. There is almost no loss of muscle mass, but a connective tissue. Instead what is lost is the fat that was stored by your body. And if you do resistive training or walking while fasting there will be actually muscle mass gain!


So diet and fasting are complete opposites of one another.

One thing to mention is that it takes time (a number of weeks) for body to get used to fasting.
And even then you still could feel hunger in evenings due to naturally elevated level of the Ghrelin hormone. So it’s not simple, but doable and has such health benefits, not mentioning fat loss, which makes it beneficial in the long run.

Weight loss is very easy when you know how

Processed Food is a blocker for weight loss

When you eat sugary and starchy foods, aka Processed Food your glucose level in the blood is high, as a consequence Insulin hormone level is also high. When it’s high fat is stored.
If you eat more than 3 times a day and have snacks between the meals Insulin will stay high. So fat will continue to accumulate in the body.
Fructose in processed food is very harmful too, but it’s for another post, meanwhile check what Dr. Robert Lustig has to say about it.


Drop Insulin level by constraining when you eat, which is called eating window. I have on average 5 hours eating window and 19 hours of fasting time.

Research shows that having 8 hours eating window could be enough for body to switch to burning stored fat.

My emphasize is on the word could. This is because it’s not enough to follow 8 hours eating window. Because if you do, but continue to eat Processed Food, fasting for 16 hours could be not enough to use all glycogen stored in muscles and liver. If this happens your body won’t switch to burning fat at all.

So weight loss algorithm is simple

  1. Have at most 8 hours eating window and 16 hours of fast time.
  2. Eating sugary and starchy food during eating window prevents you from losing weight during 16 hours fast.
  3. Walking or doing resistance training at the very last hours of the fast, when body switched to using stored fat as energy speeds up the fat loss even more.