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Intermittent Fasting FAIL? You're Not Alone!

Several years ago, I tried intermittent fasting when it first became all the rage. Result? I was hungry all day and ended up binge eating that night. I'd been on a low-carb diet for quite a while.

I now know that the problem was likely low cortisol. I've had symptoms of low cortisol all my life: allergies, wonky blood sugar, sinus infections, and recently, my three-month bout with bronchitis--in the summer. And I'm hypothyroid, a condition that tends to go hand-in-hand with low cortisol.

Cortisol helps regulate blood sugar. Without enough cortisol you can get hypoglycemia; your liver won't make enough blood sugar. In other words, I need to eat breakfast, lunch and dinner. When I had a more stressful job, I also needed some snacks in between.

Since about half of people with thyroid problems also have adrenal problems(1), and Syncrap (levothyroxine, a thyroid medication) is the second-most prescribed medication in the US(2), low cortisol must be a pretty common condition. Yet I rarely read about any caveats with regard to intermittent fasting. When Chris Kresser published an article saying he didn't recommend fasting for his patients with wonky blood sugar (that is, most of his patients), some Jason Fung fanboys chimed in with suggestions to drink enough water, eat enough fat, and of course exercise. Water and fat are necessary nutrients, but they don't fix endocrine problems. Further, drinking water without any salt can make you feel worse if you have low cortisol. (In fairness to Fung, he wrote that people with too much cortisol shouldn't fast, but doesn't say anything about low cortisol.) Kresser writes that fasting raises cortisol levels (and therefore blood sugar), but for someone who doesn't make enough cortisol, it seems to me that fasting would cause hypoglycemia.

Obviously, intermittent fasting isn't on my to-do list for 2020. I'll eat breakfast, lunch and dinner with plenty of fat and salt and few carbohydrates. I'll take my adrenal and thyroid medicine and my supplements. Nassim Taleb defines rationality as what leads to survival, which often means ignoring some of the experts.


  1. Stop the Thyroid Madness Updated Revised Edition by Janie Bowthorpe, page 47. Laughing Grape Publishing, 2019.
  2. Prescriber Checkup By Ryann Grochowski Jones, Lena V. Groeger, Charles Ornstein, ProPublica, Updated February 2019. Accessed January 1, 2020. https://projects.propublica.org/checkup/

Comments

Galina L. said…
Regularly as a FB group admin I come across interesting cases. Sometimes some people develop sleep problems, increased irritation, even high blood pressure while eating less often. When somebody complains on such set of problems I always ask how often the individual eats/or advice right away to eat an extra meal a day. So far everyone got better. I do come across benefits of fasting very often, however, humans do have individual differences
jeangenie said…
Thank you for this post. It describes me in a lot of ways. Sinus infections and hypoglycaemia - in the middle of the night I can be so hungry that I have to eat to get back to sleep. I don't know about thyroid. I've never had occasion to have it checked but I know I have trouble when I try intermeittent fasting. I can manage to push breakfast back to lunchtime but then I eat something before bed or in the night. I'll follow your links and investigate further. Jean x
Lori Miller said…
Good to hear from you, Galina! I agree people need an individualized plan.

Jeangenie, I'd recommend a 24-hour saliva cortisol test.
Val said…
Belated holiday greetings Lori! (Damn, this holiday season seemed to come & go even FASTER than in years past!)
My latest numbers from my DIY thyroid tests were improved and I am feeling a little better (generic levo & Thyro-Gold) although still plagued by fatigue & cold intolerance...
I just have to wait it out for the rest of our (relatively mild) Texas winter - but 32 degrees this AM made me anxious to finish up in the barn & return to my toasty lil’ farmhouse!
Lori Miller said…
Dr. Davis says free T3 and free T4 should be in the upper half of the reference range. He also recommends taking 500 to 1000 micrograms of iodine per day in the form of kelp tablets.

I think my cold tolerance is a lot better, but it could be the mild winter we're having.

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