Anatomy of a Fast
Disclaimer: I am not a medical professional. Consult your physician before trying this or any other dietary and/or fasting regimen. If you try to mimic this fasting protocol you do so at your own risk.
This timely link from the esteemed Dr. Jason Fung perhaps best explains the difference between “Calorie Restriction”– capital “C,” capital “R”– that is, eating at some caloric deficit below maintenance, versus the generic calorie restriction from fasting. Once again, minimizing insulin is the key factor to maximizing weight loss: The Fed and the Fasted State
AM Bodyweight: 210 pounds.
Per my last Workout Blog, my one meal of the day prior to fasting was approximately 2,000 calories with only 40 calories coming from carbohydrates and 200 calories coming from protein. The remainder of calories came from fat.
Clearly, dietary protein was low– even by RDA standards. Not quite a “fat fast” but fairly close. Protein will increase insulin levels, though not to the extent of carbohydrates, and I wanted to get a jumpstart to the fast.
I’ve been in ketosis for the better part of six-weeks now, so I’m not anticipating too much difficulty transitioning into the fast.
Two-hour post-prandial glucose measured at 81 mg/dl and the ketone beta-hydroxybutyrate (B-OHB) measured at 2.2 mmol/L.
AM Bodyweight: 208 pounds.
Today went as any other day. I normally only eat one meal a day, in the evening after my workout. I have a planned deload this week and didn’t workout today.
I drank only coffee, water and unsweetened tea.
I did notice some hunger this evening, but it quickly passed. I can only suppose my biological clock was anticipating my daily meal.
I feel a bit more (nervous) energy than usual; in the first few days of fasting catecholamines ramp up your energy levels to entice you to get moving and find food. This is consistent with previous fasts; and, if previous fasts are any indication, I don’t expect to get much sleep tonight.
I had to urinate several times. Most likely water loss as I burned off glycogen.
Perhaps I just drank too much coffee.
At approximately 24 hours since my last meal glucose measured at 51 mg/dl and B-OHB measured at 6.4 mmol/L.
Yes, my blood sugar is low. No, I’m not hypoglycemic. I’ve been as low as 35 mg/dl (after fasting for 96 hours) with no ill effects.
That said, I have had one episode that I would characterize as hypoglycemia– I was about 60 hours into a fast and ran on the treadmill for 45 minutes.
An hour later I felt weak, shaky and was sweating– I ate a couple of Quest Bars and felt better almost immediately.
Since then, I don’t do cardio any later than 12 hours after my last meal (that is, the morning after my evening meal). Fasted weight training, on the other hand, has never been an issue.
See the 72 Hours section for more detail.
AM Bodyweight: 203
I slept better than anticipated last night. I went to bed at 11:30 PM and was out by midnight. I woke up at 5:30 feeling refreshed.
I don’t suppose I burned 5 pounds of bodyfat the last 24 hours so the obvious explanation is that the vast majority of weight loss was from water released as I burned off glycogen. That would explain the frequent urination that I noticed yesterday.
Once again I only drank coffee, water and unsweetened tea. I consumed a couple grams of table salt this morning and again later in the afternoon to replenish sodium and a gram of lite salt in the evening to replace potassium.
No workout again today. I plan to lift tomorrow evening– weight, sets and reps will depend on how I’m feeling.
All in all, much easier than yesterday. There were no fleeting episodes of hunger and energy levels were fine, I wouldn’t characterize them as “nervous.”
At approximately 48 hours since my last meal glucose measured at 46 mg/dl and B-OHB measured at 6.7 mmol/L.
AM Bodyweight: 203
I slept well the night before. I went to bed at about 11 and woke up at 5:30 again.
Energy and mood was stable. No feelings of hunger whatsoever.
The only ill effect is extremely noticeable “keto breath.” I can’t smell it, but I can certainly taste it.
Once again, I only consumed water, coffee and unsweetened tea. I also took a couple grams of table salt for sodium and a gram of lite salt for potassium.
I measured my glucose and B-OHB before working out today and they came in at 44 mg/dl and 7.8 mmol/L, respectively.
I hit the weights for a light deload session today, details are posted here.
The workout went well. A few minutes after the workout I measured glucose and B-OHB again. Glucose increased to 61 mg/dl and B-OHB dropped to 6.1 mmol/L.
In my workout post I linked to an article by Dr. Peter Attia where he similarly measured the effects exercise had on his glucose and B-OHB levels. He also saw an increase in glucose and a decrease in B-OHB post exercise following an intensive resistance training session that included a lot of anaerobic conditioning work (sleds, plyometrics, etc.).
Again, my glucose and ketone levels saw a similar change following today’s workout, although not to quite the extent as Dr. Attia’s. Today’s workout was a light deload session of just a few sets with no anaerobic conditioning involved, after all.
On the other hand, his low-intensity aerobic work lowered glucose and increased ketones. Although I didn’t test my levels at the time, I’m sure this had something to do with my hypoglemic experience following the 45 minute cardio session mentioned in the 24 Hour section of this post.
Although I don’t have the data handy, I have measured glucose and ketones after a morning fasted cardio session and noticed a decrease in glucose and increase in B-OHB. However, this was while eating a ketogenic diet with a once-daily meal, so the fasted cardio session followed no more than 12 hours since my previous meal.
I do think cardio on a ketogenic diet is perfectly fine, perhaps even preferable– especially if refueling strategies have a role to play in a particularly long distance effort.
But doing cardio on a fast of any prolonged duration is going to seriously test the limits of the ability of B-OHB to replace glucose as fuel.
I strongly advise against it.
AM Bodyweight: 199
I’m looking really “flat” with little muscle tone or vascularity.
I broke the fast at the 92 hour mark with a meal of eggs scrambled in cheese and butter. It was probably the best scrambled eggs I’ve ever had, even when you consider I hadn’t eaten in nearly four days.
Final glucose and B-OHB measurements were 51 mg/dl and 6.0 mmol/L, respectively.
While I had planned on a five day (120 Hour) fast, I can’t really say why I decided to call it quits. I wasn’t necessarily hungry, but I did feel strangely compelled to eat something.
I’d probably chalk it up to boredom more than anything.
I suppose I’ll return to the once-daily, keto meal regimen as usual.
While I’ve lost 11 pounds in four days, I’m certain it was mostly water so I’ll continue to track my weight every morning to see just how much weight loss was “real.” If I had to guess, I suppose I’ll be around 206 this time next week.
Update (19 June 2017):
Weighed in at 206 this morning.