Apr 20

The Fasting Disaster


Fasting has been all the rage lately. Jimmy Moore and Jason Fung released a book on it that quickly shot up the New York Times Best Sellers list. In fact, it has been so popular that they launched a podcast on it at the beginning of this year. Oh, I did I mention the episode featuring Jason Fung and fasting is still the most downloaded of the 2 Keto Dudes podcast?

Yet other high profile low carbers such as Dr. Stephen Phinney are not part of the fan club. My personal favorite article on the subject was Not So… Fast… (A Rant) from the prolific Amy Berger.

While on low carb myself, I’ve only ever intentionally fasted for 14 hours at a time, which was only done to meet the requirements of a blood draw. But while I don’t feel hungry when fasting, I don’t feel… right.

To be sure, I’ve wondered if I want to eat all the time so that I either maintain or gain weight, given I’m underweight right now. And therefore my feeling odd when not eating is perhaps entirely mental manifestation. Regardless, a fast of a few days probably wouldn’t be that bad anyway, right?

The Experiment

The plan was pretty simple:

  1. I’d take a blood draw in the morning at the beginning of the fast.
  2. Fast for three days while both supplementing and keeping electrolytes high, but otherwise drinking only water.
  3. Take a final blood draw for comparison on the morning 72 hours after the first blood draw. So in all, 86 hours will have passed since my last meal, making it a total of 3.5 days.


Day One: I was surprised to find I wasn’t hungry at all. This seemed to back up my theory that if I had already made the commitment to myself to forgo eating, my brain wouldn’t send me subconscious “shouldn’t we be eating?” signals.

As happens with me when I’ve lowered my total calories for an experiment (but while still being keto), I feel run down and puny. I have an overall feeling of lower energy. I also feel a little dispirited in this state, but its hard to tell how much of that is annoyance of that phase of the experiment vs it being an actual physical response.

However, that not-feeling-right sensation I mentioned above?… I was certainly getting that signal. But I had hoped I’d only feel it on the first day.

Day Two: I still wasn’t feeling hungry. And while I did continue to feel low in energy, it wasn’t notably better or worse.

However, the not-feeling-right sensation was definitely much, much higher. It was like nothing I’ve experienced before this point. In my imagination it was as though my body found a red phone line and called some special center of my brain to say, “ABORT! ABORT!” No physical pain, no odd changes in the senses, nothing other than a feeling… a feeling this was terribly wrong.

By the evening I decided to go ahead and cut the experiment short. I’d take my blood on the morning of Day Three as opposed to Day Four. Heck, at least it was a 2.5 day fast in the Data Can. I just knew I’d feel annoyed if my numbers had hardly changed. (Just writing that last sentence makes me laugh out loud now…)

General Bloodwork

In every blood draw now, I get a slate of general panels like a CMP and CBC. The latter is known as a Complete Blood Count and has 14 markers. These numbers always been in range… until this time.


Ref Range 3/21/17 3/23/17
RBC 4.10-5.70 5.02 5.85
Hemoglobin 13.0-17.0 15.3 18.1
Hematocrit 37.0-49.0 44.6 52

All of these markers have to do with red blood cells and their functionality, which I won’t cover here. What I really wanted to see is if I had fallen off on my electrolytes, which would explain both the run down feeling and my general sense of malaise.


Ref Range 3/21/17 3/23/17
Sodium, Serum 134-144 137 136
Potassium, Serum 3.5-5.2 5.1 5.8
Calcium, Serum 8.7-10.2 9.6 10.5

Interesting — instead of being under, I was over on K and Ca.


Of course the big one is the lipid profile. And if you follow me, you already know what I’d predict after fasting for the very first time given the Inversion Pattern –> a record increase in LDL cholesterol.

So what happened? I hope you’re sitting down for this….


Ref Range 3/21/17 3/23/17 Difference
Cholesterol, Total 100-199 371 479 +108
HDL-C >39 72 70 -2
LDL-C 0-99 284 368 +84
LDL-P <1000 2068 3348 +1280
Small LDL-P <=527 <90 546 +546
Triglycerides 0-149 76 205 +129

Indeed it was a record!

Let’s unpack a few things:

  • Like the Extreme Drop Experiment from last year, this one had a heavy shift in dietary energy, as in a sudden drop off. And likewise this huge degree of change broke the Inversion Pattern with LDL-P, while still demonstrating its general direction (lower fat = higher cholesterol).
    • Given the pattern up to this point, we’d have expected LDL-P to land around 2200, but it instead landed much further upward at 3348. This is strikingly consistent with with the drop experiment that likewise overshot in the other direction (from 2597 to 1487 in three days!).
    • Yet LDL-C would be expected to land around 355 +/- 22 and sure enough it landed at 368.
  • While I don’t like doing these huge shift experiments, I am glad they continue to reinforce the general mechanics of the Inversion Pattern and further establish its nature.
  • Once again Small LDL-P pops up in a low dietary energy context.

Final Thoughts

  • While the experience wasn’t great, the data from this experiment was golden! As predicted, the Inversion Pattern kicked in and demonstrated just how fast cholesterol can rise while fasting, particularly for a hyper-responder like myself. I guess that last bit doesn’t actually sound like good news, but don’t worry, the blood test taken just 4 days later (not shown) had my Total and LDL cholesterol drop down near where they were on 3/21.
  • I already didn’t enjoy fasting for even a half day before this experiment… now I’m very sure I don’t want to fast for longer either. This might be something I’d consider if I weighed more, but probably not. The incredibly alarming feeling I experienced was something I’d prefer to leave in the past.


Hat tip to James DiNicolantonio who pointed out my Uric Acid likely had likely risen and I sure enough it proved to be true:

Ref Range 3/21/17 3/23/17
Uric Acid, Serum 3.7-8.6 5.8 8.2

I run a script that captures every marker outside its reference range and (unfortunately) mostly noticed those that did. Technically, Uric Acid was still inside, but obviously moving upward fast. Would it have gone above range had I been fasting another day? Alas, I’m now unwilling to find out anyway.

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92 Comments on "The Fasting Disaster"

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Very similar experience for me.
1. Ketogenic diet for several month
2. fasted for 4 days (96hs) before blood work
3. blood work 14 days later (eating “normally” and not being in ketosis)

Fasted 4 days ===>>> eating “normally” + not in ketosis
Tot Col 434 ====>> 338
Trig 109 =======>> 92
LDL-C 337 ====>> 259
HDL 75 ========>>61

Theresa F.

For some reason, I’m not concerned with my cholesterol going up while fasting, nor does the ‘hunger’ that lasts maybe a minute bother me. I feel it’s merely psychological since anyone burning fat has plenty to ‘eat’ in their fat stores. My energy is good, I feel fit and my HA1C went down from 6.7 to a steady 5.4. The effortless weight loss and almost total lack of carb cravings is a real relief, as well, but to each their own. 🙂

Nicole recine

The electrolytes likely reflect dehydratation. I hope you rechecked them since. Those being abnormal can cause heart arrhythmias


Do you think dehydration contributed to the changes? Particularly in light of the CBC changes?


Brilliant article


Why is a TC of 371, DL-C of 284 and LDL-P >2000 GOOD??


I’m wondering what this would look like on a non hyper responder Dave. Any hypothesis on whether it might have something to do with the results?


I wonder if what you saw here was actually a good thing (if done in the short term, not chronically?!

If in fact fasting stimulates autophagy, then perhaps we are seeing blood cell turnover where you made lots more and then the old ones get broken down.

Similarly, since cholesterol is involved in so many repair and production processes such as hormone precursors.

Julie Gregory

Hi Dave,

Another fascinating experiment! The folks at ApoE4.Info (www.apoe4.info) have been closely following your work with admiration. We applaud your citizen scientist approach to understanding the role of cholesterol. We’d like to invite you to speak with us at the LowCarb San Diego event in August. We’re especially eager to hear more about what you’ve learned about being a hyper-responder of dietary fat. I suspect your work may have implications for our population. Please contact me at: [hidden] for details. Thanks for your consideration.




Fascinating as usual! I’ve asked you think on Twitter but to reiterate, what I really want to know is: based on lipid response to fasting, when is the ideal time to measure lipids to give the absolute *best” insight into future CHD risk? Is it best to do one in the middle of a normal day, one 12-14 hours fasting, and perhaps one just after a meal?


Macro Four

Interesting that you found fasting uncomfortable. I have done two three day fasts always breaking them for social reasons rather than for feeling unwell. The difference is I am chowing down mostly on my own on body fat as I am overweight. My understanding via the 2ketodudes protein episode is that there is an upper % limit to the body fat you can convert so It makes sense that if fasting when not overweight your body would signal discomfort at eating too much body protein.

Thanks for putting up with your pain mistress called science!

Macro Four


I’m not interested in fasting at all, but am always about 14 or 15 hours fasted when I have my cholesterol checked and I have high total (around 300), high HDL, low trigs, high LDL and high particle count. I wonder if I tried getting tested after breakfast if I would have a better reading? I have not heard of a hyper responder to fasting before.


you should get it checked normally like you do after a 14 hour fast but eat high fat for the three days before like Dave Feldman has done. That will work better.


Is it known if the ratio of cholesterol to other “passengers” in LDL and VLDL stays constant? Or could it be that when the body needs more fat due to e.g. Fasting, the relative amount of cholesterol in LDL and VLDL goes down.

So you see a rise in VLDL and LDL but there might not be a change in the bodies’ total circulating cholesterol?


Incredible short term changes, what do you think the long term effects would have been, for people doing 10+ day fasts? Gene changes would kick in?


(Minor typo with small LDL-P: +564 -> +546)


I see exactly the same effect in my tests. So the implication is to stop fasting because it drives LDL to unhealthy levels?

Leigh Yaxley

Why assume that the LDL levels are unhealthy? That’s just the old paradigm with which we have all been brainwashed.
Some people in this world are short and some people are very tall. Is it dangerous for them to be so different to the average height of the human population.
I think the same applies to cholesterol.

Fleur Brown

How about repeating the experiment but trying a 16/8 fast for a few weeks by skipping breakfast….you may lose some weight though.
Dr Mark Hyman who says he needs to keep his weight up as he is very slim, eats some starches like sweet potato to ensure he doesn’t lose weight so when you eat after the 16 hour fast you may need to add in some low GI starchy carbs perhaps.if you start losing weight.
Dr Terence Kealey has written a very illuminating and interesting book on skipping breakfast ” Breakfast Is A Dangerous Meal “….

Just got lab results today which flabbergasted me. I have been on the extreme LCHF version of my diet needed to actually lose weight (I shoot for 500-1000 cal, 90% from fat and most of that saturated fat). BTW, doing LCHF for over 5 yrs. Cholesterol numbers are through the roof for me: LDL-P 2260 LDL-C 227 HDL-C went down from my usual range and is at 53. What interests me about my results are the high Triglycerides (168) and high glucose for me (104). Any speculation about what would drive these numbers up due to my near-fasting? If I… Read more »
I wonder if the rise in your numbers with fasting is a type of stress response. I am a hyper responder and recently noticed a huge rise with acute stress – in a nutshell, I was admitted to hospital and very worried, cholesterol on admission 250, then sent home next day thinking all was ok, relaxed, then 3 days later got the results I wasn’t ok and spent the next 4 days in hyper stressed mode worrying myself sick. Cholesterol was 350 at next appointment! 10 days later in reduced state of stress, cholesterol was 227. This was all psychological… Read more »
Hi dave Thanks for providing such a useful information. I’m an hype-responder too and never tried longer than 14 hours fasts. Maybe one day I’ll try it with your experiment in mind to see if I can stand it. Apart from that, I’m wondering why Lipid tests don’t include NEFAS (Non Esterified Fatty Acids). If I’m not mistaken they take some part in the Lipid trafficking in the blood stream the difference being that they don’t come bundled in Lipoproteins but are bound to Albumin. Isn’t this a missing data point in any study about Lipid levels ? To my… Read more »
Nils Hoernle, MD
Hi Dave; These are curious results (speaking as a doctor who looks at lab results all day every day). The high potassium is surprising, and could be from hemolysis during the blood draw (the needle tip not being exactly in the vein slices the passing red cells open, releasing potassium). Or from the electrolytes? Also, it’s unusual to see a true bump in Hct from one day to the next unless it’s from vascular volume loss (so the increase is relative to the decrease in blood serum). Fasting, we know, causes insulin to drop and Glucagon to rise, thus mobilizing… Read more »
Leigh Yaxley
Dave, I have a simple explanation to offer. Here goes: 1) Since you are well adapted to LCHF your metabolism is primarily utilizing fat for energy. 2) During the 3-days of low fat consumption (and especially low fat + calorie deficit – the extreme drop) you are effectively ‘starving’ your metabolism and it will compensate by cranking up lipolysis of adipose tissue and greatly increasing your level of circulating free fatty acids (FFA) – akin to fasting. 3) Most people think of adipose tissue as just ‘fat storage’, i.e triglyceride (TG) storage but it is also a large reservoir of… Read more »
Bert mellinger

Occums Razer. Dave what if you redrew your charts with the following formula: Fat= Calories burned – dietary carb – dietary protein. So fat is 100% while fasting. And while in a calorie deficit, fat is dietary fat plus deficit fat burned.
This would explain the continued increase in ldl p while fasting.


Hi Dave – are all your blood tests done, fasted (e.g. overnight if not ‘fasting’) and at the same time?

I’ve been in and out of keto for a few years and generally just supplement carb for intensive cycle rides. I’ve stopped counting macros but my last (overnight fasted) bloods where not so ‘good’:

HDL 82
LDL 432
TRIG 122
TC: ??!!


Interested in why you think your RBC etc increased?

Hi Dave , Thank you for sharing your findings, they are fascinating! I have been lchf for 10 years. I started out on Atkins and over the years have slid off here and there but for the most part have kept to it. Since hitting post menopause I have gone to Keto and IF. I am post trauma after being hit by a car last February so somewhat sedentary since then. I am about 20 lbs overweight and working on losing it. It’s slow going! I recently moved and on gaining a new family doctor, he ordered a lipid panel.… Read more »
Dennis Shumaker
I recently completed a 3 day 19 hour water only fast from Oct 19 430pm to Oct 23 1130am I took the blood test 45 minutes just before breaking by fast Oct 23 1043am. I do have a blood test from Oct 17, a few days prior to starting my fast. Too bad I cant post a pic of my metabolic panel and cholesterol. I too see very elevated levels of Bilirubin, AST, Total Cholesterol, Triglycerides, LDL and VLDL Before/After Bilirubin 0.5 -> 1.6 AST 46 -> 60 Total Cholesterol 183 -> 222 Triglycerides 86 -> 175 VLDL 17 ->… Read more »
I am a 55 year old woman, quite thin. I have always had reasonably low cholesterol (total around 160). But the past three months, I’ve been doing intermittent daily fasting (with a few 24 hour fasts here and there) of 19 hours (eating only between 2 and 7 pm). My most recent total cholesterol came back as 297! HDL was 91, and tryglicerides 60. As those last numbers were okay, my doctor did not recommend statins (which I wouldn’t take anyway). I do have a heart disease in my family (father died at age 55 of heart failure; not overweight… Read more »


Based on all the research documented on here, I would expect LDL-C to increase with IF.

I’m curious why you started IF, since you are already thin? (I’m in the same boat, thin and practicing some IF, CVD in family).

IMO, your lipid panel is enviable, TG/HDL of 0.7. If you are disappointed that you need to give up IF because of a TC score, I’d encourage you to get some better metrics before making a decision. At 55, you might consider a CAC test. Ivor’s talk is a great intro on that.



The effect you observed is not uncommon. See this 2014 study: https://www.sciencedaily.com/releases/2014/06/140614150142.htm. Fasting needs to be done over a period of time to see changes. What you probably experienced is your body trying to fight the sudden change by dumping more cholesterol into your blood.The inversion you speak of is probably a temporary self-protection effect, and not a long term phenomena.

Di Smith
I am female age 61. 173cms ( 5’8’). Currently 63kgs ( 139 lbs) Very active and well (athletic most of my life) I always look slim, but my body fat with calipers has always had me in the obese range! Normal weight and BMI 21. I work full time in my own business and am happy. No medications beside supplements, mg, d3, Omega 3, zinc. I have followed LCHF since 2013. 3 months ago I stopped drinking completely (was wine about 2 sometimes 3 glasses, every day) I felt it had become a bad habit. I wanted to focus more… Read more »

Hello Di,

Since we sound similar and I’m going to start LCHF soon, your post was of interest to me so I found this that you might be interested in: https://friedmansprout.com/2015/04/01/how-does-a-ketogenic-diet-affect-you-part-3-c-reactive-protein-a-marker-of-inflammation/. Have you thought of doing IV therapy? You can get an inflammation reducing cocktail and that might help these numbers. Just a thought!
Best wishes!


Hi Traci
Thank you, the article was interesting and happily, I believe I know what was causing the high CRP so will not do an IV therapy. My CRP is usually very good. Best wishes with the LCHF lifestyle:)

Abhishek Anand
It is interesting to note that your small LDL-P rose that much. My small LDL-P hardly budges: it stays between 1040-1089 even when my LDL-P fluctuates between 1617-2295. Steve Phinney and others have proposed that during fasting, the body mobilized the cholesterol stores in adipose tissues. https://www.ncbi.nlm.nih.gov/pubmed/2035468 I never quite understood how this happens. Do the adipose tissues directly store LDL particles which come back to circulation after weight (fat mass) loss? Or fresh LDL particles from the liver visit the adipose tissues and there stuff in more cholesterol from the adipose tissues? If one’s adipose tissues were formed when… Read more »
I’ve been doing alternate day fasting for 5 years, and I started that after moving to an all organic diet with essentially no processed foods. Some years before the alternate fasting, my triglycerides were at 100, and in those days I had a sweet tooth. I just got them measured after an eating day (so after ~12 or so hours of fasting) and they were 340. Another guy on reddit who does intermittent (not alternate) fasting, says his triglycerides are at 52. I’m not sure what to make of this. (I’ll add that ADF was very natural for me. It… Read more »

Ok, so I’ve just watched one of your talks. Here’s more data on my lipids, and this is from a person who has been doing ADF for 5 years, loves it, and has a steady weight. This was measured the day after an eating day, and so on 12 or 13 hours of fasting:

Total cholesterol: 184 mg/dL
HDL: 53
LDL: 63
Trig: 340

So my Trig’s are high, but my LDL’s are low. Hm. Do I understand correctly that it’s the LDL’s shuttling around Trigs? If one’s high, shouldn’t the other be?

I don’t know if it’s useful, but I do have some other lipids results from some years before, when I was doing nothing special for diet, other than whole, organic, foods. I was also a long-time, 28 yr, vegetarian. I would have to say that at that time, I had a bit of a craving for both sugars and fats. Total cholesterol: 189 mg/dL HDL: 50 LDL: 119 VLDL: 20 Trig: 100 So while my total cholesterol and HDL are similar to my recent test, my Trigs are more than three times lower and in the (supposedly) normal range, but… Read more »
Thanks for your reply. They seem curious to everyone else involved, too. To answer your question, no, I am not doing a ketogenic diet on my eating days. I did try a higher fat low carb diet at one point, prior to doing ADF, and found it didn’t work for me. It made me tired and foggy. Presently, my diet consists of basically: veggies, fruit, eggs, chicken, a little rice, a little fermented, gluten free bread, a small amount of nuts & seeds along with some coconut. I have just made a modification due to a UTI: I have removed… Read more »
Dawson Oliver

Your “inversion” is nothing more than dehydration. Anytime you fast you must be more hydrated than usual. When you are dehydrated everything in your blood in more concentrated so you are going to see increases in CBC, CMP, Lipids, and decreases in electrolytes. This article is utterly useless.

Douglas Hoover
My Name is Douglas Hoover- In the spring of 1975, I read 2 books by Dr. Paul Bragg, Water, The Shocking Truth, and The Miracle of Fasting. I fasted for 19 days to get rid of gout and get off the Zyloprim…Gout disappeared after 6 days. Continued fasting every year for 21 days (distilled water only) and every 5th year fasted for 40 (while working the entire time in my construction company. Fast forward 34 years, I performed 26 21-day fasts and 8 40 days fast. I know very little about biology, medicine or science! However, I do know this… Read more »