Observations Round 2 – One month of intermittent fasting

My first 30 days on this journey!

Starting May 4, 2016 to June 4th 2016 twenty intervals were recorded during this 30 day period.  The average daily fasting interval was  21.3 hours.  My shortest recorded duration was 13 hours.  My longest recorded duration was 71 hours.  The graph below is exported from the Fasting Secret Pro app.

graph fasting secrecte may 4 to june 4 2016

Since I am new to fasting and am self-managing fasting intervals lasting longer than 24 hours, 71 hours was the longest I felt comfortable fasting, though when time came to break the 71 hour fast I felt fine and likely could have easily continued. My weight decreased by 17 pounds and my body fat percent decreased by 8.7%.  The data that the Tanita measures to be included in future observations are muscle mass, BMR and metabolic age. I have read a lot about different intervals/types of intermittent fasting and the success folks experience with them.  Because I tolerated fasting quite well and felt so much better once incorporating fasting, I pushed my limits more than many of the generic beginner recommendations out there.  I read a lot prior to starting and would have certainly shortened any interval if needed.

I attribute having followed a LCHF/keto lifestyle for a number of months prior to beginning to fast intermittently to a number of things:

  • A smaller percentage of the weight I lost initially was water as glycogen was already partially depleted (related to the significant drop in percent body fat)
  • Fewer/minimal negative reactions associated with initially fasting like headaches and fatigue.
  • Fewer cravings and feelings of hunger
  • I have read that hunger during fasting is due to the process of glycogen depletion. The biochemistry is likely more complicated but that makes sense in that my hunger does subside significantly during longer fasting intervals
  • Switching to fat burning sooner/more efficiently after eating stops
    • Low insulin levels are needed for your body to access stored fat
    • After eating, a post-absorptive phase lasts about 6-24 hours
    • Insulin levels decline, glycogen is depleted and fat stores are accessed for energy
    • If less glycogen is created then it would seem that fat burning would begin sooner
    • If you are keto-adapted your body is better trained to shift to fat burning


Other general observations

  • The first few days, I felt that I was drinking a lot more water than I was voiding. Then I experienced the opposite. I think this was due to insulin levels dropping due to being fasted.
  • I was very conservative regarding activity during my first month. Having no idea how I would tolerate fasting, I did not want to over-do anything as it had been a while since I did regular exercise anyway. Going forward, I will begin to incorporate exercise.
  • The optimal fasting interval for me may be 24 – 48 hours
    • To ensure that my body is past the post-absorptive phase and maximum fat burning is taking place and to train my body to become an efficient fat burner while I am working on decreasing insulin resistance.
    • To ensure that muscle mass is preserved
      • In ketosis, the body uses free fatty acids for energy which minimizes the need for amino acids and so preserves muscle
      • Mobilization of protein is passive as a result of decrease in insulin
  • Decreased appetite and cravings due to ketosis are very helpful
  • Breath mints are your friend
  • I am more insulin sensitive but still have a way to go; adding exercise will have an impact here.
  • A number of planned break fasts have been around dining out/social situations. I did attend a work related dinner at Ruth’s Chris and took the meal home to eat the next day. It is a testimony to fasting/ketosis that the rampent smells of butter on steak and my favorite creamed spinach did not faze me.


I will point out that the article Keto-adaptation: what it is and how to adjust does a good job of explaining the biochemistry of glycogen storage and excess glucose (carbohydrates).  It basically reads that the reason we initially lose a bunch of weight quickly when we go on a diet is due to depleting glycogen (and lower insulin levels).  Fasting, as well as exercise, deplete glycogen.  The reason this point is significant for a LCHF/keto lifestyle + fasting is carbohydrates consumed are very low thus less/no glycogen is being created/replenished. Simply stated keto-adaptation is shifting your metabolism from relying mostly on glucose for fuel, to relying mostly on fat-based sources of fuel by significantly reducing the availability of glucose/glycogen.

Also, physiologic and metabolic adaptation during fasting has a nice grouping of figures that explain the phases that I alluded to in the above observations.

More to come.