Carb Nite® Experiment Complete

NOTE:  In my earlier release of this post, I incorrectly reported my "After" HgA1c value as 5.7.  It was actually 5.2.  I've now corrected that error.

Back in November I began an experiment to see what effects a diet called "The Carb Nite Solution" would have on me.  You can read about what I was trying to do here, and some of the progress in my experiment here and here.

The approach of Carb Nite® begins with a foundation of a very low carb diet, punctuated with evenings where a significant amount of carbs are consumed leading to a sharp insulin spike.  This spike is said to trigger better insulin and leptin sensitivity, and the approach prescribes a carb night approximately every week.

With that background I intended to see if;

  • Carb Nite® would have any impact on my insulin sensitivity
  • The spike in glucose from the Carb Nites would be compensated by the increased insulin sensitivity the rest of the week, as measured by hemoglobin A1C
  • I felt any different
  • I observed any other health, weight, or other changes

I've completed my experiment.  I did the test for about 3 months, with the first Carb Nite on November 13, and the last on February 11.  In a sentence, I've concluded that, for me, the experiment likely did improve my insulin sensitivity over that period of time, and that this was not enough to compensate for the spike in glucose about once a week since my HgA1c increased somewhat, and that, for me, I did not like the impact on my feeling/health.

This is MY Experiment

Before diving into the details, I want to emphasize that this was an n=1 experiment, an experiment with only one subject, me.  As such, part of these observations might have just been due to chance, and may only be the way this stuff affects me.  These may not be the things that would happen to anyone else or it may not even be typical for any group of people.  In other words, "your mileage may vary."

On the other hand, n=1 experiments are valuable because sometimes what happens to the masses, doesn't happen to us individually.  By testing on oneself, we know for sure what the changes we tried do to us as individuals.

Insulin Sensitivity

Before starting this experiment, I did my own "home brewed" glucose tolerance test.  The idea of a glucose tolerance test is to measure blood glucose for a period of time after ingesting a fixed amount of glucose to measure how your body processes it.  If you are insulin sensitive, blood glucose will spike up and drop back down to normal relatively quickly.  If you are insulin resistant, blood glucose will spike even higher, and take longer to drop back to normal.

I did the test about a week before starting the first Carb Nite® and then did it again about a week after the last carb nite.  My results are shown in the graph below.

From the graph, it's evident that in the "after" test, my blood glucose didn't spike quite as high, and came back down to baseline more quickly than in the "before" test.  This would indicate that the experiment likely improved my insulin sensitivity somewhat.  (Keeping mindful of my caution above though, I don't know if it's normal for my insulin sensitivity to vary from day to day this much so with a one time test like this, it is certainly not conclusive.)

This result is plausible however, so I believe it's probably true.  When people, including me, first start practicing a low carb or particularly a ketogenic diet, it takes time for the body to adapt and begin to rebuild the enzymes and cellular structures needed to process the additional fat and adapt to using fat and ketones for fuel.  It certainly makes sense that after about four years of using next to no glucose for fuel, my body would not be as good at processing it.  By forcing my body to process a spike of carbohydrates periodically, as in this experiment, it would stand to reason that it would get better at it after 3 months.


If my insulin sensitivity is improved with Carb Nite, does that mean I'm healthier?  In an attempt to assess that, I also did a Hemoglobin A1C test before and after as well. HbA1c is a measure of "glycated hemoglobin" in the blood.  Hemoglobin is a molecule in red blood cells that transports oxygen.  Glucose in the blood reacts with hemoglobin causing the hemoglobin to become glycated.  The more glucose in the blood over a period of time, the more glycated hemoglobin is present.  When blood cells are formed the hemoglobin isn't glycated.  Over time it becomes more glycated depending on how much it is exposed to glucose in the blood.  Blood cells have a lifespan of about 3 months so at any given time you should have some fresh blood cells and hemoglobin and some old blood cells and hemoglobin.  HbA1c is a measure of the concentration of glycated hemoglobin and thus is a good measure of the average blood glucose levels over a period of about 3 months.  It is also more or less a direct measure of the effect that glucose has on the tissues and systems in your body.

HbA1c is measured as a percentage which can be roughly correlated with an average blood glucose level over that 3 month period.  Typically "normal" is interpreted as around 5% which is estimated to correspond to an average blood glucose of ~97 mg/dL"

My "before" test of A1C was 4.9%.  My test after the experiment was 5.2%, a slight increase. This tells me that in this experiment, for me, the weekly spikes in glucose may have been large enough to affect my body in a negative way -- enough that the insulin sensitivity benefit couldn't compensate.


Weight is one of the least accurate measures related to health and yet it's the one we all seem to look at.  I didn't make a significant attempt to track my weight throughout this experiment but I did take a look at before and after.  It looks like my weight went up about a pound and a half.  The problem with weight though is that you probably need about a five pound difference to be significant at all.  

I do also use a body fat measuring scale, and my body fat percentage went up about 1/2%, which again, is very much within the range of error since this measure is very sensitive to other factors such as level of hydration.


One of the most significant things I detected throughout this experiment was my general perception of how I felt.  As the experiment progressed I just didn't feel as good.  I didn't seem to have the usual energy that I have had since I switched to a low carb approach.  I also started to get heartburn more regularly.  Not just on the days I consumed carbs, but throughout the whole week.  Prior to this experiment, I literally didn't have heartburn for almost 4 years since adopting low carb, and it completely went away within a couple weeks after ending the experiment. Finally, despite no measureable change in weight, I have felt like I have gained weight, particularly around the waist.  It's possible some fat redistributed to around the waist (not a good thing) or I'm feeling some bloating, or it's just psychological.


Another observation I made towards the end of this experiment relates to a potential increase in systemic inflammation.  Two health issues I dealt with over the course of this experiment were a cold that I had trouble getting rid of, and a bout of plantar fasciitis in my left heal.

I have had maybe two colds since I originally switched to a low carb approach but then I got another one while doing this experiment.  The other two colds were over within a couple days and were mild.  The one I got while doing this experiment I just couldn't seem to get rid of.  While I believe the actual infection was gone within about a week, I had sinus pain, and significant congestion for over a month.

The issue with my heal is something I have had on and off for most of my adult life.  Once I started wearing proper shoes (I found that a brand called San Antonio Shoes (SAS) almost completely cured the issue.) Even when It cropped up again after moving to a house with a slab foundation (with floors that don't have much flex) I could still take care of the issue with proper stretching exercises and utilizing the proper shoes.  Since starting this experiment however, this has gotten much worse, enough that it was painful all day, difficult to walk, and forced me to visit a doctor who confirmed the plantar fasciitis diagnosis.  While his modified exercises and topical anti-inflammatory helped, it hasn't gone away.  I'll have to see if it continues to get better now that I've discontinued the carb nite experiment, but it has started to improve.


As with any n=1 experiment, it's impossible to make hard and fast conclusions for a trial like this, particularly any that would apply to anyone but myself.  For me however;

I believe that this approach did improve my insulin sensitivity.

I believe that my metabolism and health was negatively impacted by the approach and that this was likely due to my particular sensitivity to carbohydrates.  (I believe I would probably be diabetic, if not for practicing a very low carb approach.)

This approach isn't right for me (although I do recognize that Carb Nite isn't necessarily intended for continuous practice.)

It might still be good for me and certainly would do no harm to do a high carb day (probably with more "healthy" and whole foods and less sugar) on occasion.  Perhaps just a few times per year.

I feel much better and my energy has returned now that I'm back on a very low carb/ketogenic approach.

I recognize that since this is a one time, n=1 experiment, a lot of the observations could be based on random variation and in fact, the cold and the plantar fasciitis could actually have led to the increase in HgA1c instead of the other way around.  With a single test like this, there's really no conclusive way to tell, but I suspect that it's the sugar spikes that led to the inflammation instead of the converse.

I'm now about a month into my next experiment which i'll describe in a future blog post.  You can get a bit of a hint about it by looking at my book list on the home page (or the link reproduced here) where I list all the related books I've been reading.  (The most recent at the top of the list.)  If you'd like to purchase any of those books, please use the links provided which take you to the page for the book.  If you buy a book, or anything else on Amazon, from one of those links, it helps keep this blog going.