Cyclic Ketogenic Diet and Thyroid Hormone

Thyroid GlandCyclic Ketogenic Diet and Thyroid Hormone

Brief Summary:

Recently I completed a 10 week experiment doing a variation of a cyclic ketogenic diet called the Carb Nite Solution, which basically entails eating strict low carb (less than 30 gm per day) with one 6-8 hr window of massive carb loading per week.  At the end of this experiment, before going on a trip to Italy, I had a series of fasting labs drawn.

So far we’ve looked at my:

I’d now like to explore my thyroid hormone levels (if you want to learn more about the basics of thyroid physiology I go into it briefly in one of my earlier posts).

Carb Night Thyroid

One of the main purposes of adding the Carb Nite according to Kiefer is to prevent the body from slowing down it’s metabolism.  This is important because as you can see from the above numbers, after doing 90 days of nutritional ketosis, I became hypothyroid (subclinically hypothyroid depending on who you ask).  You can see that after adding carbs back into my diet, my thyroid numbers drastically improved!  So it looks like having some carbs/insulin onboard is necessary for me to maintain my thyroid function.

After 10 weeks of Carb Nite, my thyroid hormone levels didn’t take too much of a hit.  It looks like the 1-2 days of carb refeeds really did the trick in preventing me from becoming hypothyroid.  The TSH did go up from 1.23 to 2.23 and my RT3 is still higher than I would like, but it these numbers definitely aren’t as bad as what I saw after 90 days of pure ketosis.

On Jimmy Moore’s Livin la vida low carb podcast, Chris Kreser came on as a guest host and discussed how going low carb can have detrimental effects on your thyoid (you can listen to it here).  This podcast was serendipitously released yesterday!

Here’s are some highlights:

  • Low carb diets can cause hypothyroidism
  • One way to address this is simply to add carbs back into diet
  • Insulin required to make conversion from T4 to T3
  • People who do very low carb and people who fast, who have low insulin levels, show a decreased conversion of T4 to T3
  • This can cause no issues in people… OR these can cause worsened hypothyroid symptoms in people.
  • Can supplement with selenium (fish and brazil nuts) and zinc (red meats, organ meats, shellfish) which will help improve conversion of T4 to T3.
  • Must make sure iodine levels are sufficient
  • Reduce inflammation and stress (which also decease conversion of T4 to T3, decrease TSH output, AND decrease sensitivity to thyroid hormone)


Having the 1-2 weekly Carb Nites really did provide enough stimulation to my thyroid to prevent hypothyroidism.  I’ve read in some places that an optimal TSH is 1.00 or less…. and my RT3 is definitely still too high, but as you can see, this is still much better compared what I found after being in uninterrupted ketosis.

I suspect that the hypothyroidism from being in ketosis too long contributed to my limited weight loss.

After 12 weeks of nutritional ketosis, my umbilical circumference only changed from 34.5 to 33.5 inches and my weight only decreased from 180 to 178 lbs.  Not a very significant change at all… hard to believe that hypothyroidism didn’t play a significant role in these paltry results.



When I woke up this morning, it suddenly occurred to me that my supplement stack was different during this time around compared to when I did straight ketosis.  One of the components that I added in was Mark Sisson’s Damage Control Master Formula which has Selenium, Zinc, and Potassium Iodide in it, among a host of other things…

So with this confounder, I can’t say for certain that the carb refeeds were 100% responsible for my thyroid levels…

Image credit from

17 Responses to Cyclic Ketogenic Diet and Thyroid Hormone

  1. mike says:

    At the end of the day, I do not hear many people saying calories do not count. At some point even Peter Attia and Mark Sisson admit to lose fat you need a small caloric deficit. To confuse the situation they just say “don’t count calories” eat the right foods and you will naturally lose fat. So if a person is not “estimating” calories, how can they troubleshoot? They cannot. To even estimate well, you have to weight the portions of at least the majority of food, which then becomes obsession over the diet, which is not healthy either.

    Here is what I am thinking in your case. Did you have higher ketone levels during the ketogenic diet than you did during Carb Nite? Your Carb Nite ketone levels were low, which may in itself explain the thyroid being stable. Could it be the carb refeed? Sure, it could be that too. On average, I would say you may have been deeper into ketosis that first time around though. Again, it becomes a matter of spending money and measuring and obsessing. I am ok with that, at least to understand visually, portion sizes and blood numbers.

    There are also people like Ron Rosedale that say a lower thyroid is a perfectly normal response to a ketogenic diet and it no cause for concern. The potential thyroid issues are why I avoided the low car diets until now. I admit I was “sucked in” by Keifer’s assertion that a large refeed would assure my thyroid stayed normal.

    I do now firmly believe sugar, sugar in processed foods, french fries, buns, sodas, Gatorade, bagels and sugared coffee are the real problem.
    But we need some real answers on how to lose fat, reliably, safely, long term and feel safe that lowered thyroid is ok. Hopefully Nusi will figure this out in testing.

    Have you calculated your protein %’s from Carb Nite and your keto experiment? I think you need to do that. If you were always well above 30% protein, you most certainly could have been turning it to sugar and burning it and your lean mass rather than fat. Your comments about “still being hungry” sounds like protein acting like sugar to me.

    As a caveat, while I know a lot about this, I am not a success story yet. I am just going by what I hear, which can be a problem. Listening to too much conflicting advice usually makes people not follow one plan correctly.

  2. Cheryl says:

    Hi BJJ Caveman, I used to follow your posts when I was on LCFs. I was wondering your thoughts on going on a ketogenic diet, and if its realistic or not. I am an endurance athlete mainly but also do some weight lifting. I did NK for about a year but found that I lost more muscle mass than actual fat mass (revealed through DEXA). I also consulted some medical professionals and personal trainers. Some of which stopped short of calling me anorexic. I also developed a bad problem with abdominal bloating. I looked about 7 months pregnant and it took them awhile to figure out what was causing it. I eventually had to stop the LC diet, increasing the protein first and then the carbs. Things are back to normal now. Do think its really realistic for athletes to do NK? I’m just curious because my experience with it wasn’t all that positive.

    • Mike says:


      First let me say, a ketogenic or ULC diet, if done properly, has been proven to be the most muscle SPARING diet on the planet.

      It is “supposed to” allow weight loss in a caloric deficit, while potentially sparing 90% of muscle, while losing fat. The amount of fat you eat, NOT protein, is what causes the muscle sparing.

      Without trying to offend you, were you eating properly on the ketogenic eating plan? How much endurance training was going on?

      1. Did you eat enough calories to not cause starvation mode?
      20% maximum cut in calories, 15% safer.
      This is INCLUSIVE of exercise calories being lost due to cardio.

      2. Adequate protein 15-20%, no more than 25%.

      3. 70%-80% fats. Coconut oil, butter, fish oil, avocados.

      4. Plenty of hardy vegetables, greens, occasionally berries.

      If your someone doing a lot of endurance training, that will eat muscle every time. It also increases cortisol, especially in women, which in turn, will cause your body to hold onto fat stores.

      Do you have detailed food logs of that time period? If not, you may not truly be able to blame the ketogenic diet.

      Overeating protein causes the body to learn to burn protein like glucose.
      From that point, once in a caloric deficit, guess what, the body will burn muscle as glucose.

      Endurance activity, coupled with not enough fat intake or too high a caloric deficit, could certainly cause what you are describing. Especially, if your doing high heart rate training for more than a few minutes 2-3 times a week.

      You can check out Jeff Volek’s presentation about Ketogenic diets from the low carb cruise on youtube. He and Stephen Phinney have proven multiple times in medical studies on athletes, that they lose fat and GAIN muscle on a ketogenic diet. Some gain a large amount of muscle.

      Am I qualified to state this personally? I am on day 60 of a Cyclical Ketogenic Diet. According to my tracking I have lost between 15 to 20 pounds of fat and no apparent loss of muscle, as measured by stopwatch in weight sessions.

      My follow up Dexa scan will confirm if I have lost lean mass. However, I do not think Dexa can truly measure “muscle”, only lean mass. Which includes bone and possibly other tissues and organs.

      To sum up, caloric deficits and endurance training, cause lean mass loss.
      It is the bodies natural defense mechanism.

    • BJJ Caveman says:

      I can’t add too much more than what Mike kindly wrote.

      The biggest concern I’d have with what you describe is not enough calories, plain and simple.

      Everything I’ve read indicates that ketosis is the most muscle sparing sort of diet there is…. as long as there are enough calories, and enough baseline level of protein (the formula I remember is 0.5-1 gm of protein per pound of body weight).

      When you did NK before, did you confirm it with blood ketones?

      Abdominal bloating – did you have any other GI issues going on at the time? Did you have any intake of gluten? Dairy? A lot of fiber?

      Ultimately, if things are back to normal with you right now, and you are happy with where you are, then NK might not be the best for you.

      I believe NK works very well for a lot of people… but that being said, I believe more in self experimentation, to truly discover if it works for you… after all everyone is different, and what works or someone else might not work for you… hence my own continual experimenation.

  3. Hemming says:

    How many grams of carbohydrate did you consume on the carb nite? What kind of carbs was it?

    • BJJ Caveman says:

      I was eating anywhere from 200 – 300 gm.

      I tried to make it mainly clean carbs, like rice and potatoes… then other things started sneaking in there like peanut butter cups and gluten free cupcakes and an occasional pizza or cheesecake.

  4. Hemming says:

    I forgot to ask. DOes Kiefer mention in the Carb Nite Solution how much fat and protein to eat depending on your weight and goals?

    • BJJ Caveman says:

      He gives some simple meal plan break downs in the Appendix section. Very generalized.

      An Example is “Simple Menu Planning, Lower Calorie Day 1” – with a meal plan for the entire day and a macro break down at the bottom of “usable carbs 10 gm, Fiber 12 gm, Fat 99 gm, Protein 144 gm”

      Or “Simple Menu Planning, Higher Calorie, Day 7” – with a similar but more dense meal plan and macro break down of “Usable carbs 15 gm, Fiber 20 gm, Fat 135 gm, Protein 194 gm.”

      • Hemming says:

        Thanks for both of the answers. I actually thought that Kiefer did give some guideline as to how much to eat depending on your goals. Anyway, I think I’ll pick up his new book once it launches…

    • Mike says:

      There are sample menus, but I do not think he would agree with them anymore, for most people. Specifically, the amount of protein advised is probably too high for most.

  5. Cheryl says:

    I was just curious of any other athletes have had negative results on a Ketogenic diet. I personally loved the diet, and I did drop down to 5% bodyfat, however I also lost a lot of lean muscle mass as well. I have all the Volek and Phinney books, listened to the podcasts and followed all the rules. I was on it for about a year, it didn’t work for me. The bloating was just undigested food, I am not exactly sure what caused the buildup yet, but right now I am back eating simple carbs and proteins and it has improved a lot. I didn’t get the results from being in NK or the high fat/low carb diet, that I wanted. In fact I did better on the high carb/high protein/low fat diet. I didn’t like that diet as much but at least I only lost fat mass as opposed to fat and muscle.

    • mike says:


      Dexa confirmed I lost 13.5 pounds fat and only .75 of a pound lean mass in 3 months. I weight train for 15 minutes once a week. My trainer said a normal dieting person would have lost 4-6 pounds of muscle in losing 14 pounds of at. Ketogenic diets spare protein and muscle breakdown. My proof is there.

      If your a woman who got down to 5% body fat, any diet would have lost muscle, that is a danger zone for men let alone women at 5%.

    • BJJ Caveman says:

      I’m glad you brought up this point. Ben Greenfield in a few of his recent podcasts actually brought up the issues he faced doing ketosis while training and performing in long distance iron man type of events. There were some benefits, but ultimately he found that things were too difficult, and he’s actually no longer doing it.

    • BJJ Caveman says:

      Also just wanted to ask, were you following your total caloric intake during this? The fact that you were losing muscle mass may have indicated that you weren’t meeting your caloric and/or protein needs.

      I’d be interested to hear more about your experience.

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