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Laura: Five Day Fasting-Mimicking-Diet including my Protocol, CGM, Ketones, and more


This post is for education purposes only and is in no way medical advice. You should consult with your doctor before doing any diet or exercise.


I completed a five-day fasting mimicking diet (FMD) in the first part of June. The FMD was created by Dr. Valter Longo to mimic water fasting as water fasting is generally not tolerated by the average American. See Matt’s write up here for the beneficial effects of the FMD. I did modify my macronutrient intake compared to Dr. Longo’s FMD; I ate closer to 15% carbohydrates and 75% fat to enter ketosis more quickly while keeping his recommended protein consumption.

This is the second FMD that I have completed. The first time, however, I ate whatever I wanted within the calorie limits and my protein intake was way too high. Below I give the reasons why I decided to go through with this fast, what I did to succeed in completing the fast, and my data from the fast.


There are two main reasons why I wanted to do a fast before starting residency:

1. Improvements in metabolic markers. The endpoints of fasting are well studied and reported. For an example, refer to Matt’s FMD write up which shows that 3 months of FMD improves many metabolic markers, including blood pressure, fasting glucose, triglycerides, LDL-C, and CRP.

2. Changes in the biochemical milieu of cells. The three main cell signaling pathways that cause a differential response within cells in the fasted start are mTOR, AKT3 (Protein Kinase B), and AMPK. These pathways are responsible for the beneficial effects seen in reason number 1 and many other effects such as autophagy. A future write-up will be devoted to each of these pathways and their exact effects on the body.

Strategies and Tactics


Magnesium chloride. 2 teaspoons a day (except 1 on Day 1) mixed in with pickle juice (see below). Reason: prevention of presyncope/ lightheadedness. I took this supplement at baseline and as needed for lightheadedness. Each time I got light-headed I took magnesium chloride or pickle juice with water.

Magnesium citrate. I supplemented with magnesium citrate to help keep a regular bowel regimen.


Pickle Juice. I wanted to find a source of concentrated sodium without any calories or additives and pickle juice, specifically the brand Bubbies’, fit this role perfectly. I had 2-8 tablespoons of pickle juice per day depending on how light headed I felt.

Topo Chico. These mineral water beverages were a great way to get more water throughout the day. I drank all three flavors of original, lime, and grapefruit as needed for rehydration.

Decaffeinated Coffee. Matt and I decided to stop our caffeine intake during our fast. Our reasons were two-fold: 1.) a caffeine holiday would decrease our sleep latency and hopefully improve our sleep in our hungry state and 2.) caffeine on a caloric deficit/ fast would most likely cause a resting tremor and anxiety. Still, we love the taste of coffee so we opted for black swiss water process decaffeinated coffee.

Intra-Fast Data and Pictures

Food. Below are tables of the macronutrients and times at which I ate and drank. Additionally I included pictures of the food I ate. In the charts below, the % calories does not add up to 100. This is due to the fact that some of the calories and macronutrients reported on food labels are slightly off (for ex. the chocolate is reported as 160 calories in a serving, but if you do 4*4 + 14*9 + 8*4 = 174 calories). I followed the FMD protocol very closely, except I opted to eat more of my calories from fats rather than carbs to help stay in ketosis.

Left: Food to be eaten. Right: Prepped dinner.

Left: Food to be eaten. Right: Prepped dinner.

Left: Prepped dinner. Middle: My favorite 100% chocolate bar. Right: Delicious snack.

Zero App. I used the zero app to record how long I fasted each day. Day 1: 18hr23min. Day 2: 17hr34min. Day 3:19hrs18min. Day 4: 16hr32min. Day 5: 19hr11min. Day 6: 13 hrs.

CGM and Ketones Data. The following graphs detail my blood glucose and ketone levels while on the fast. The CGM data was relatively precise and accurate when tested against the Contour next finger stick glucose monitor. The average of the differences between the CGM and the finger stick monitor was 6.9 mg/dL as seen below. There is a lag in the CGM behind the finger stick glucose reading because the CGM measures the interstitial glucose vs. capillary glucose of the finger stick. My actual blood glucose was almost always lower than what the CGM was reading.

The green zone on the graphs below is the same as the green zone on our CGM data page and runs from approximately 60 to 116 mg/dL. This range signifies our preferred ranges for glucose variability and will be covered in Matt’s next write up. My average glucose for day 1 was 104 mg/dl, day 2 was 92 mg/dL, day 3 was 110 mg/dL, day 4 was 85 mg/dL, day 5 was 71mg/dL, and day 6 was 89 mg/dL.

Nutritional ketosis is defined as a ketone level >0.5 mmol/L. This is the threshold at which your body begins to switch from glucose to ketones for its primary energy source. I hit this threshold on day 2 of my fast.

Coke Zero*** from day 3 above. I almost never drink sodas, artificially or naturally sweetened beverages, but I decided to indulge and get a medium coke zero from the movie theater. I had about 8 oz over the course of 30 minutes while checking my blood sugar every few minutes. I was very confused at the subsequent large CGM spike because Coke Zero is supposed to have zero carbohydrates. At home I tried a can of coke zero to see if that would affect my glucose, which it did not. I do not know what the theater gave us, but it was not coke (different flavor per my brother who knows his sodas) and it was NOT coke zero.

Blood pressure, Pulse, Weight, and Subjective Feelings. I logged these parameters into the table below.


Fatigue and lightheadedness. These were the two main symptoms I experienced. I did not take any naps during the fast as I wanted to be able to fall asleep as easily as possible at night. The pickle juice and magnesium chloride definitely helped with the amount of presyncope/light headed episodes I had compared to the first time I completed the FMD.

Another interesting symptom I developed was hiccups. Three different times I got the hiccups, and they lasted for at least 10 minutes. Only once did I develop a pounding sensation in my heart. It went away after about 20 seconds and I immediately had some water with pickle juice, and then a topo chico.

Hunger. Day 2 was the worst day of hunger. Even so, I would categorize it as moderate hunger (using a scale of mild, moderate, and intense). My hunger never went above mild after day 3. Instead of hunger pang being a symptom that I needed food, it was more a sensation of light headedness and difficulty focusing that cued me that I was “hungry”.

Sleep. I slept very well during the fast and did not struggle to fall asleep at night, except on day 5. Day 5 was probably one of the worst night sleeps I have had in a long time.

Headache. I had no headaches at all during the fast. I was slightly surprised as I expected at least a caffeine withdrawal headache as this was the first time in probably 4 years that I did not have caffeine in the morning.

Exercise. The day before the fast I did a ton of exercise, including tennis/swimming/kayaking. Most days I did some type of physical activity or movement. Sometimes it was very difficult to feel motivated to exercise with the low energy levels, but I always felt better after completing the exercise. Next fast I would like to do more weight lifting and cycling.

Breaking the Fast

Breaking Fast Meal. I broke my fast with a high fat, high protein, low carb meal that consisted of 8 oz bone broth, 3 scrambled eggs, ½ onion, guacamole and spinach with Cholula. I was only able to eat about half of my plate until I felt uncomfortably full and had to wait until lunch to eat again. A high protein meal is essential after a fast to induce IGF-1 levels to stimulate new cell growth after the fasted state. A low carbohydrate meal is also essential as muscle is insulin resistant after a fast due to the ketosis state.

I would have liked to stay eating low carb for a few more days after completing the fast, however, I through my brother a surprise birthday party before moving out of Florida and so enjoyed cake and ice-cream with him for lunch and dinner. The two glucose spikes around 3 pm and 5:30 pm are from the cake and ice-cream.

Alertness. After eating breakfast I felt absolutely amazing. I had so much more energy than I had in the previous 5 days – it felt great. I continued to have tons of energy many days following the fast.

Weight. I believe the weight I lost was a combination of subcutaneous and visceral fat, and some muscle. However, during the fast I made a new personal record in the number of pull-ups I could do, 8! I have started lifting weights again and cycling and do not feel like my muscle mass/stamina has been impaired at all. I also increased my bone-broth / protein intake during this post-fast time.

Modifications for the Next Fast

Collection of More Biomarkers. There are many additional biomarkers that would be fascinating to measure pre- and post-fast to determine how an individual responds to a water fast. These include, but are not limited to, measurements of LDL-p, Lp(a), cortisol, thyroid function tests, LFTs (if previously elevated), hs-CRP, oral glucose tolerance tests, insulin, antibody tests if autoimmune disease is present (anti-TPO, anti-gliadin, anti-SS-A,, etc) etc. The results of these tests would be more for intellectual curiosity rather than clinical use but long-term trends after single fasts or multiple fasts could have implications for individualized treatments. Additionally, a daily point of care chemistry panel would ensure no electrolyte derangements.

Schedule More Activities. Fasting is boring. An immediate realization is how social and enjoyable eating is and you will certainly miss it over the fasting period. Filling in extra time with fun, active activities such as putt-putt or long walks would help pass the time.

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