Extended Fast: Background and Goals

I realize I’ve gone total tech bro with my passion for keto and fasting but ohmygodyouguys, keto and fasting.


This isn’t my first extended fast by some definitions. Prior to this, the longest fast I’ve done was 105 hours – 3 days before my last round of radiosurgery and one day after. I also did 4 days when transitioning to lorlatinib. This time I set my sights for 7 days before starting my new, complementary metabolic therapy.

Read about my first 3-day fast here.

The overarching goal of my way of eating is to keep my blood glucose-ketone index (GKI) as low as I can, spending as much time as possible in the therapeutic range below 1.0. Over the past several months I’ve found that the best rhythm for me is a 40-70 hour fast at the beginning of the week to reset my GKI and then one giant, multi-course meal a day (OMAD to the bros) on the other five or six days. In reality, I usually have two meals on Sunday and fast again until my morning GKI is under 1.0 as it tends to slowly rise over the week.

I’ve been checking my GKI almost every morning and some afternoons since February. What impresses me most is how dramatically non-diet variables will have an impact. I now have instant feedback on the way stress and sickness raise my blood sugar and clear evidence of how exercise can lower it.

Maggie’s GKI (Glucose-Ketone Index) Over Time

Morning fasted GKI tracked since Feb 12. Note that these are overestimates due to my glucose monitor calibration but the trend is valid. (note below)

On a few occasions I’ve tracked my GKI through the course of the day to understand the fluctuations. You can see it’s naturally higher in the morning, the “dawn phenomenon,” but highest after my daily meal. It might be worth moving my daily meal to first thing in the morning so that I can maximize my time spent in the lower ranges but for now I have to be practical with my work schedule. Plus, once I eat, my mental clarity is shot.

GKI (Glucose-Ketone Index) Throughout the Day

GKI through the day
  • The blue, red and yellow lines are a standard Thursday, Friday and Saturday. You can see how my GKI slowly rises as the week goes on and I’m further away from my fast.
  • The green line is a day after having too much carbohydrate and protein (1770 calories, 35g net carbs, 65g protein, 143g fat the previous day – this is fewer calories than the night before the blue line but the wrong distribution of macros).
  • Finally, the orange line represents a deeply fasted state (day 6 of this fast, actually).

A Note on Accuracy
One note about all GKI numbers: The FDA only requires glucose meters to be accurate within 20%. To test mine, I took it with me to the hospital on blood test day and tested within the same minute I had my blood drawn. My keto mojo gave me an 87. The hospital lab results came back 72. This is barely within the FDA accepted range and means all my GKI readings may be 20% higher than they really are. Awesome news!!

Extended Fast Goals

I think it’s important to understand the ‘why’ of a thing before doing it. Personally, I want to:

  • Get Healthy. I’ve been pretty destroyed since Beijing. I’d been hoping to rest last weekend but instead spent 30 of 60 hours in a plane in a mad rush to get my drugs and get back in time to go straight from international terminal to office. My edema secondary to lorlatinib has been out of control, the lymph nodes under my jaw (not known tumors) have been super swollen, and I’m just plain exhausted. I know from experience and human history that fasting helps me heal.
  • Spend as much time in the therapeutic zone of low low GKI as possible. Starve out those cancer cells while arming my healthy cells with sweet sweet ketones.
  • Enjoy the massive immune benefits including a complete recycling of my immune cells around days 3-5. Out with the tired soldiers, in with fresh reinforcements!
  • Enjoy the autophagy benefits and rid my healthy cells of the broken parts that fuel cancer.
  • Give my organs a rest. My digestive system works overtime on the massive amounts of raw veggies I feed it. My liver and kidneys are constantly processing the nutrients and toxins even in my mostly organic food. I declare a week long vacation for everyone! Well, a working vacation. No one gets to take real time off.
  • Curiosity. Leaving this out would be a lie of omission. I’m super curious what it’s like to not eat for a week and whether I can do it.

This all needs to be done before starting the Care Oncology metabolic protocol which happens immediately after my upcoming trip to the Mayo. Plus, with Brad out of town for the month there are fewer temptations.

I have the perfect window of opportunity!

Next: Extended Fast Results & Experience Summary

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