Do those 40+ mile weeks do only good things to your body or could they be hurting you ? Is all this exercise catabolic ? Have you ever heard of hypothyroidism ? How about screwing up the hypothalamus-pituitary-adrenal axis ? If you are a chronic exerciser you might want to read on.
Define catabolic: The metabolic breakdown of complex molecules into simpler ones, often resulting in a release of energy.
“I tried to rescue my Jessica from the clutches of the cardio contingent, but to no avail until a month ago when she called to tell me that a blood test had confirmed her doctor’s suspicion: she had hypothyroidism — her body no longer made enough thyroid hormone. Her metabolism slowed to a snail’s pace and the fat was accumulating. Now she had a culprit to blame, it wasn’t the cardio causing her problems, it was her body rebelling. When Jessica asked my advice, I told her to do two things: schedule a second test for two weeks later and until then, stop all the goddamn running.”-From the article, Women Running into Trouble. By John Keifer, on Elitefts.com
There are plenty of studies showing that chronic cardiovascular workouts may help to shut down the thyroid gland and its production of T3 thyroid, the body’s metabolic regulator. If you need those references, the 2 articles in this blog post, one by Keifer and one by Kresser, have plenty to just get you started.
Wait a minute Gait Guys, months ago you wrote about gluten in my food affecting the thyroid and now possibly longer cardio exercise as well ? Yup, there are suggestions that it can be the case in many people. But that doesn’t mean you need to freak out. You just need to be aware and be smart.
First, lets review the gluten thing one more time for our new readers. (if you want to read our gluten ataxia article from moons ago, here it is). Several studies show a strong link between AITD (autoimmune thyroid disease (both Hashimoto’s and Graves’)) and gluten intolerance. The link is so well-established that researchers suggest all people with AITD be screened for gluten intolerance, and vice versa. And some experts will even tell you to not trust the intolerance screens, rather just stay away from gluten all together.
AITD is a case of mistaken identity says Dr. Kresser in his article. He mentions that
“the molecular structure of gliadin, the protein portion of gluten, closely resembles that of the thyroid gland. When gliadin breaches the protective barrier of the intestinal gut, and enters the bloodstream, the immune system tags it for destruction. These antibodies to gliadin also cause the body to attack thyroid tissue. This means if you have AITD and you eat foods containing gluten, your immune system will attack your thyroid”
Ok. Back to exercise now.
OK Gait Guys you have my attention now. So, you are telling me that regularly repeated sustained exercise can also possibly affect me as well ? The answer is yes. There is some reasonable and growing research on this topic, so just educate yourself and make your choices and watch for signs.
Here is how it works. T3 is the body’s metabolic regulator and it can crank up to generate heat and fuel production through catabolic processes generating energy. It can also down-regulate (hypothyroidism) to slow the body’s metabolism and lower body core temperatures. This slow down can cause weight gain and lethargy even if the person is active and exercising (Do you ever go to the gym and see those folks who are always on the treadmill or ellipticals, never seeming to lose weight ? Sure they could be eating 3 square meals at Crispy Creme but it could also be their thyroid). When T3 is in balance the body can regulate temperature and energy production without problems. Thus it can be extrapolated that long standing steady exercise (floating around that 65-75% VO2max) will generate long periods of increased body core temperatures and energy expenditure raising the watchful eye of the thyroid. If it could talk, the thyroid would be saying, “Hey, what’s going on out there guys ? Why are we cranking up the heat and blowing all these fuel sources, EVERYDAY !? ” And since the thyroid is always on this alert, it is watching for signs it needs to REACT to preserve the organism and its energy stores. So when it see these long periods of increased temperature and energy expenditure it naturally senses that it must intervene to preserve them. Thus, it drops T3 output, temperature drops as well as metabolism. The brain and hormonal regulatory feedback systems decide then that the problem is solved, the organism can survive to live another day. Unfortunately for the athlete this is not a productive thing when training for a marathon, so they override the signs and symptoms and get back at it tomorrow. Now, in this state, other fuel sources become vulnerable including muscle and bone mass. Plus cortisol ramps up and we all know how destructive long term heightened levels of cortisol can be. Not only are they catabolic in sustained high levels, they alter the adrenal hormonal loops with the brain, sacrificing hormones like DHEA and pregenalone to mention only a few (ie.Pregnenalone Steal Syndrome) and their associated feedback loops.
We see alot of serious athletes with this kind of stuff and sometimes we have to order hormone panels for these problems to see just how messed up the loops are and to determine where to start. Sometimes we just look at them and ask why they think more training trumps rest and recovery.
As a brilliant doctor in these fields said to me the other day while discussing Keifer’s article, “When the HPA axis is activated, the CRH response from the hypothalamus to pituitary begins the upregulation of the adrenal axis and directly inhibits TSH. And the glucocorticoid response will also inhibit TSH. If the body is under siege and goes into a catabolic state it should naturally have an inbuilt protective mechanism to slow the rate of breakdown! ” Thank goodness our body has this mechanism !
What did he say ? In a nutshell, what he said is that the hormonal systems are all connected via feedforward and feedback loops to make sure the body is balanced and healthy. When the body is working out too much and expending too much energy, heat and breakdown for long periods of time turn on these protective feedback loops in an attempt to protect the body. The thyroid and adrenals are often at the mercy of the process, as well as your healthy hormone levels, muscle and bone mass (read more on this in Kresser’s short article) as well as energy.
Staying healthy, it is a fine line. Don’t forget that rest and recovery are critical for your performance, but more importantly for your health. A recovery day should be just that, recovery ! Not an easy 50 mile bike ride ! That is not deemed as recovery to the hormonal regulatory mechanisms of the body. This stuff bodes us to share the statement……. “more is not always better”. Don’t forget that your body needs to be fed rest and recovery just as much as good food and sleep. And, do not mistake this article to say that exercise is bad either, we all know the truth there.
There are some really great articles out there that talk about the similar physiologic effects of brief high intensity workouts when compared to sustained steady state exercise. And, they might help save your body in the process if you are one of the vulnerable ones (and there are alot of vulnerable ones !).
Want to read John Keifer’s orginal article on this, go back up to the link provided at the top of the page. We tried to summarize a very difficult topic (even for some physicians) so don’t feel bad.
Shawn and Ivo
Ya, we are a little more than just Gait Guys. We try to take care of our athletes on every level. This may not have been gait related today, but it sure was running related.