View Full Version : IF vs cortisol

Brad Davis
01-17-2008, 04:39 PM
I apologize for kinda double-asking this question. I tacked it onto the back end of and old thread and got no answers, so suspect that it wasn't noticed.

I've read that it's good to eat post-WO to decrease cortisol levels.

Why should we not be concerned about this if we IF, workout outside the feeding window, and wait many hours before eating? For example, several of my workouts lately have been at 11-12 at night and I didn't eat until 1-2pm the next day.

Actually, why should we IFers not be concerned about cortisol in general (as compared to folks who eat normally)? My limited understanding is that cortisol levels are kept under control partly by regular eating.

Thank you very much.

Garrett Smith
01-18-2008, 05:57 AM
Cortisol is not always a bad thing, it's what allows us to get out of bed in the morning.

My impression would be that we would like to have a cortisol curve that is optimal, not too high and not too low (adrenal fatigue), preferably as low as possible while maintaining our energy, faculties, and blood sugar levels properly/optimally.

Curious studies on induced hypoglycemia, not totally the same as fasting, but possibly something that can relate to your question. You decide, as a search of PubMed under "intermittent fasting cortisol" only came up with these two as things I could relate to your question:

Recurrent hypoglycemia does not impair the cortisol response to adrenocorticotropin infusion in healthy humans. (http://www.ncbi.nlm.nih.gov/pubmed/9781630?ordinalpos=4&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVDocSum)
Following exposure to intermittent hypoglycemia in healthy humans, fasting morning ACTH and cortisol levels are reduced...

Intermittent hypoglycemia impairs glucose counterregulation. (http://www.ncbi.nlm.nih.gov/pubmed/1446801?ordinalpos=6&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_RVDocSum)
Fasting (5.3 +/- 0.1 vs. 5.4 +/- 0.1 mM) and nadir (2.3 +/- 0.1 vs. 2.4 +/- 0.1 mM) glucose levels achieved during insulin infusion did not differ on study days 1 and 4. In contrast, the glucose levels required to stimulate an increase in EPI (2.8 vs. 3.1 mM), glucagon (2.8 vs. 3.2 mM), cortisol (2.4 vs. 2.9 mM), GH (2.6 vs. 3.0 mM), and autonomic hypoglycemic symptoms (2.2 vs. 2.5 mM) were all significantly lower on study day 4 versus study day 1 (P < 0.005-0.05). Basal levels of EPI and cortisol, but not glucagon, GH, or NE also were reduced on the final study day.

What could one try to take from these studies, especially without seeing the whole thing? IF, while not causing hypoglycemia per se, would likely cause a lower level of blood sugar through the day than eating multiple meals would, especially non-Paleo ones (like super insulin-spiking whey/maltodextrin/sugar bombs). In those two studies, there is apparently lowered cortisol after episodes of hypoglycemia in both healthy and diabetic subjects (I'm thinking or relating that to post workout windows here, a stretch, but the best I can do with what I found).

Interesting, as cortisol raises blood sugar, so I would assume that a true hypoglycemic episode would raise cortisol levels (unless the sum of a hypoglycemic episode, or multiple ones, is enough to fatigue the adrenals into an inability to make enough cortisol).

I think those in favor of PWO feeding and cortisol are only looking at the short-term picture. Also, they're trying to figure out the Black Box.

An observation of mine, and maybe others will chime in, is that people who do IF are likely folks who appear to deal with stress well. Chicken or the egg scenario, correlation/causation, whatever. It would appear that IFers, based on their apparent capability of dealing/handling stress on a daily basis, are not flooded with cortisol due to worry/fear/etc.

Just some thoughts.

Mike ODonnell
01-18-2008, 07:20 AM
Good question....as much as cortisol gets the "bad guy" rap (yes even from me at times) it still has a much needed purpose if we want to break down and repair/rebuild our cells....as well as other stress related fight or flight needs. I think the real fear of cortisol when it comes to "keeping muscle" is in 2 key places:

1) During an extended exercise event (usually anything over 45-60min starts the increase in corisol)
2) All day long as a "stress" response

As far as the response during the night and in the AM, I believe because of the huge GH spike during the first few hours of sleep, it is a total body response to breakdown and repair muscles and get ready the next day to start taking in nutrients and using them for rebuilding process. Also if you look at the GH response after a more brief (under 45min) high intensity session, you will see less of cortisol and more GH. But it can also in the next couple of hours reverse, so I still believe that some sort of pwo with healthy amino acids would be necessary.

It is also interesting to note that most heart attacks happen at night (most early AM) while people sleep and their cortisol is peaking. Although you would have to look at the whole health picture of those people.

Also good to note that alot of very overweight people have basically no cortisol left in them from stress all day long (burned out), that in turn has lead to the adrenal disfunction and weight gain. So stress reduction is key for many health reasons as we were meant for short bursts of stress with "fight or flight"....not all day events of "where's my report Johnson? I want it done by 3pm!".

So...in pure health, performance, muscle recovery needs...I would say this:
- Keep workouts under 45min
- Any workouts lasting hours (more endurance events/sports), may be good to sip a "small carb"/protein or fat/protein (depends on activity intensity) mix during to minimize muscle breakdown and speed up recovery
- Supplement BCAAs pre workout and pwo (especially if you are going to bed right after...get some aminos in there)
- If you want, experiment with BCAAs first thing AM while you are doing IF
- Keep stress levels low all day long....go breathe some fresh air, get a perspective on life...etc...

That right there should do you plenty good and keep you healthy.....cortisol while at times should be minimized, falls into the old nitrogen retention paranoia from old bodybuilding philosophies....and I am not going to set my alarm for 3am just to go get a protein shake...no thanks.

Garrett Smith
01-18-2008, 08:29 AM
Cortisol is only one of the body's blood glucose regulating mechanisms.

PWO supplementation helps suppress cortisol for that window (I'm not sure of the size of the window involved), as the increase in blood sugar from a PWO feeding (esp. high carb) doesn't need the cortisol to keep blood sugar steady. As for long-term cortisol response, which is what I'm interested in, I'd guess that consistent PWO hyperglycemia (and typical endurance athlete and BBer constant all-day attempts at keeping blood glucose "stable" by keeping it constantly elevated) and ensuing reduction in insulin sensitivity over time would eventually require more cortisol to keep blood sugar steady.

Excessive amounts of cortisol in the blood impair memory and other mental processes. Simply based on the observations of IFers statements of mental clarity during fasting periods (and the lack of it, or reduction, after feeding) would lead me to believe that an IFer's cortisol levels are lower than most. FWIW.

Brad Davis
01-20-2008, 04:40 PM
Thank you both for your replies. That's a lot to think about!

Mike ODonnell
01-20-2008, 07:31 PM
Wouldn't sweat it too much....plenty of people are keeping and gaining lean muscle on IF...so if your "cortisol" fear is muscle loss....the body is self regulating. Adding some BCAAs around training and in the AM may also help.

Robb Wolf
01-23-2008, 10:05 AM
If we are insulin sensitive we should see an easy shift to fat metabolism and possibly ketone production which will keep cortisol in check. As Garrett mentioned, some cortisol is not a bad thing, we just don't want to see things go too sideways.

There are some inexpensive saliva test kits for monitoring cortisol levels but a simple assessment of "am I performing better, worse or the same" can help direct whether one is going to wild with the IF.