Steady State Cardio = Thyroid Killer?


I ditched “steady-state cardio” — those endless slogs of running for hours at the same pace — a long time ago… partially because I hated it (so boring!) but mostly because smart people told me that intervals and strength training were much better options for fat loss.

But before I got smarter about my training, I did a lot of steady-state cardio. I used to participate in triathlons, and I spent hours slogging my way back and forth in the pool and dragging my ass along the bike trail, on foot and on wheels, for training. Hours. And hours. All the while monitoring my “progress” on my heart rate monitor and the scale.

Those were dark days.

Anyway, now when I run, I only do intervals. Sometimes the intervals are more like sprints, sometimes they’re more like jogs — but the total sessions never last more than 30-35 minutes and the intervals themselves never go for more than three minutes. My heart rate bounces around like a drop of water in a super-hot skillet.

But even knowing what I know and doing what I do, I have to admit that sometimes, when I think about how I “need to get serious about losing the 15-20 pounds I gained during the thyroid-adrenal adventure,” the scared, emotional part of me wonders if I should be running or jogging or swimming or biking for extended periods of time, instead of the short bursts required by throwing around barbells and lifting weights faster.

My rational mind knows the smart move is intervals, heavy stuff, and walking. But Emotional Me is pretty lame sometimes. Emotional Me is all, like, Ohmygod. I should totally be running for 90 minutes every day to get thinner.

Then Rational Me tells Emotional Me to read this article: Why Women Should Not Run

Before you react to the title of the article, let me explain that it totally supports the idea of high-intensity interval training (HITT) while it deconstructs the dangerously entrenched idea that steady-state cardio is a good idea for women.

Here are two powerful quotes that are particularly relevant for (a) women with hypothyroidism and (b) women who want to lose excess body fat.


“Studies demonstrate beyond any doubt that in women, cardio chronically shuts down the production of the thyroid hormone T3.”


“Training consistently at 65 percent or more of your max heart rate adapts your body to save as much body fat as possible. After regular training, fat cells stop releasing fat the way they once did during moderate-intensity activities. Energy from body fat stores also decreases by 30 percent. To this end, your body sets into motion a series of reactions that make it difficult for muscle to burn fat at all. Instead of burning body fat, your body takes extraordinary measures to retain it.”


The article is supported by a lengthy list of references and does a nice job explaining the science without getting too technical and overwhelming. It’s just the right combo of common sense and science to give me the confidence to stick to my interval path.

Read the whole article: Why Women Should Not Run


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  • Jennifer says:

    I am both (a) and (b) and this is just what I’ve been thinking. I am new to Crossfit, on Day 12 of my Whole30 (no cheating! woot!), and cannot imagine doing this without your blog. I love your recipes, advice, tips, and humor. And I bought your cookbook and am working through it! Thank you!!!

  • Heather A. says:

    About 7 years ago I went through some huge life changes that resulted in depression and access to mass quantities of junk food (for the first time in my life!)- not surprisingly, I started to gain weight.

    Like a lot of people, I took up running. And gained. And so I ran more. And gained. Then started biking, gained, did a triathlon, gained.

    All told, I gained 50lbs in a year while being more active than any other time in my life! I was eating “healthy” aka whole grains, no more fast food, and yet still I gained steadily.

    When I quit running, I lost about 20lbs in the course of 4 months without really trying. I started eating Primal ala Mark Sisson and lost another 15.

    I still shake my head at how I trained hours each day for six months for a triathlon and ended up losing a whopping FOUR POUNDS in that whole time! I am glad I have learned better, but man.. I really wasted my time and potentially harmed my health in the process.

  • I read this article recently and was just telling my husband about it when your blog popped up in my facebook feed. I fall into both categories: woman with hypothyroidism (due to Hashimotos) and a woman who wants to burn fat. I am considered “obese” on the BMI scale (I’m 187 and 5’3). The problem is I do like long distance running. But I also love CrossFit. and I’m torn. I have a race coming up next month, but after that I supposed my long runs will go out the window. It makes sense, as I saw more fat loss in the first few months of CrossFit than I did with years of running. Thanks for expounding on this!

  • Melissa says:

    I read this today and it makes me sad. While I love intervals, I also like running longer distances. I’ve been lifting heavy and running for a couple of years.

    Unfortunately my thyroid and other hormones are tanked. One day I may have to give it up for good, but I am trying to balance both if possible

  • Thu says:

    Yeah, I will admit that the tone of the article (as well as the title) rubbed me the wrong way at first, but I did read it all the way through, and I understand what it’s trying to say, beneath all the ranting.

    However, I do not run to lose weight. (And also, I HATE treadmills.) I run, a LOT, because I love it. It is something I enjoy. It’s my zen time. I crossfit and I paleo (do you like how I made those verbs?) for my body; I run for my spirit and my mind 🙂

    • Naomi says:

      I too, thought the article was poorly written… very crass. I can totally relate to the zen feeling! You just totally let go and you’re in your runners world… love it.

      • Dallas says:

        Naomi, I think it’s worth pointing out that an article isn’t “poorly written” simply because you don’t like what it says. It’s not considerate or prudent to attack other people’s perspectives based on feeling threatened by the implications if the author is, in fact, absolutely correct, as Melissa is. A little respect is due, in my opinion.

        • Naomi says:

          I did NOT say I felt it was poorly written because of WHAT it said. It did not like HOW it was said, and I too am entitled to my opinion in this public forum on the WORLD WIDE WEB.

          The first paragraph of this article upset me followed by “Nobody told these people to do these things”. ACTUALLY THEY DID.
          When I got the gym tour and instruction when I first started working out before I owned a computer and had the capacity to do my own research, I followed what the idiot who worked at the gym told me for 2 years. I did what my fit friends told me to do…. RUN! Some people may not know exactly what to do when they are starting out at the gym, but at least they are starting out.

          I didn’t like this article because it
          1. Written insenuating that people who do steady state cardio are idiots, which is unfair because they are obviously doing what they think is the right thing to do
          2. Acts like stopping steady state cardio is the cure all. It’s not. I’ve been doing HIIT workouts for 2 years, and I eat clean, more recently paleo. I still suffer from low t3, low t4 and a myriad of other symptoms.

          I fail to see how my former comment was an attack, and I don’t understand why you needed to say that I am threatened and not entitled to “attack other’s perspectives” when, apparently you are.

  • Dallas says:

    Interestingly, high-intensity interval training does a pretty good job at temporarily reducing the conversion of T4 into T3 (, which is one reason that I see so many secondary hypothyroidism cases in functional medicine patients who overdo the frequency of their HIIT. HIIT is a powerful but double-edged sword, and in folks who have secondary (non-autoimmune or subclinical) hypothyroidism, the metabolic stress (and thus hypothalamic perception of stress) of HIIT can be yet another roadblock to normalizing the HPA and HPT axes. Thanks for sharing this topic with your readers.


    • Mel says:

      Thanks for weighing in, Dallas! I’ve been keeping my HIIT to once a week because of my thyroid issues. Generally speaking, would you say that’s a good idea, or do you think HIIT is off the table for us thyroid freaks?

      • Mel says:

        Also, WHY IS IT ALWAYS MALES?! Don’t the scientists care about us ladies?

        “OBJECTIVE: To compare the thyroid hormonal responses to high-intensity interval exercise (IE) and steady-state endurance exercise (SEE) in highly trained males (n=15).”

      • Dallas says:


        I think the once-a-week bombing is acceptable, if for no other reason than to convince yourself that you’re still badass. 😉 It’s also important to note that very short (<10 minutes or so, though there's nothing magical about that number as a threshold) stuff drives less of a stress response (central to downregulation of the HPT axis) than long-AND-hard stuff. Hence… our longstanding case against the Sexy Metcon. Of course, a truly all-out effort for 5 or 8 minutes can also drive up cortisol, though it's less likely to do so than an all-our effort for 20 or 30 minutes. It's the combination of hard AND long that's the real killer. I recommend actual *interval* work for thyroid folks. CF-type workouts are not typically interval sessions – they're most "get it done as fast or as hard as you can" deals. For secondary hypothyroid folks, I like a work:rest ratio of 1:2 or 1:3 (or even full recovery), meaning you get some decent recovery between hard intervals in combination with higher volumes of low-intensity stuff – like you're already doing! 🙂

        • Mel says:

          Thanks for clarifying! I’m sure that will be really helpful for people who are trying to sort out how to best take care of themselves.

          I have to admit, I DESPERATELY want to reduce my work:rest ratio when I sprint, but I’ve been sticking with 1:2 and 1:3 and telling myself that badasses rest hard. 🙂

          • Rach says:

            As another lady with thyroid issues (yay, Hashimoto’s!), this conversation between you and Dallas has been so, so useful. I work very hard at NOT beating myself up for the lack of cardio in my workout schedule, since it was so ingrained in my head from the stupid-teenage-years that MORE CARDIO = thin. It’s refreshing to read people discuss the actual science, rather than spew “fitness” “facts”.

            I’ve got more reading to do, but thank you again for this post 🙂

          • Erika says:

            A big thanks for the discussion and clarification between you and Dallas! I am two weeks into my scaling back completely from CrossFit and running in order to better manage my hypothyroidism and newly diagnosed adrenal issues. I’m having a super tough time being ‘okay’ without the all-out-max-effort WODs and long distance running. Maybe it’s my competitive nature? In any case, Mel, thanks for sharing your story and, Dallas, thanks for sharing your expertise.

          • Krista Golish says:

            I am really happy that I stumbled upon this post and especially yours and Dallas’s discussion. I was diagnosed with hypothyroidism within the past 6 months and was wondering why it all of sudden was an issue for me. I had been crossfitting regularly for about a year prior to the diagnosis, about 4-6 times per week. I’ve gained weight and had severe digestive problems for a year despite eating paleo most of it… And four doctors later they can’t figure out the digestive issues. I’m wondering if I need to cut back on the number of metcons I do weekly and focus more on strength/lifting and skills? Plus add walking back into the mix. Melissa, would you mind sharing your weekly “schedule” of what you do for exercise? Walking/Crossfit/strength/yoga… I’d love to be able to get this all under control and back to “normal”! Or if there is any updates to this info since it was originally posted?? Thank you!

          • Hi, Krista! It’s taken about 2 years for me to get my adrenals and thyroid dose back in good working order. For a while, I stopped all exercise and just walked… then I added strength training back in. Meanwhile, I was working with a functional medicine doctor to heal my adrenal system and get my thyroid dose right. I also did a lengthy elimination diet to fix digestive issues. I finally got all excellent blood work at my last set of blood tests and have the green light to start doing some high intensity workouts again. I work with a personal coach to make sure my workouts are right for me, and I use a heart rate monitor and HRV monitor to make sure I’m not over-taxing my body. I recommend that you find a functional medicine doctor that can partner with you to sort out all your stuff — it’s complex and if you have adrenal issues along with your thyroid stuff, there’s not an overnight solution. Sorry I don’t have better news! But the good news is that you can heal yourself and feel awesome again.

            My current workout schedule looks like this:
            walk 10,000 steps every day
            epsom salt bath at least every other day
            strength training plus a short (5-10 minutes) metcon 3X a week

            I’m also trying to get yoga back into my schedule to help with workout recovery and stress management.

        • Eric says:

          I was going to comment citing the article about HIIT, and ask if anyone had some insight on how these two articles played together. Thanks for getting down to the nitty gritty on that, Dallas. That’s a nice clarification for me.

  • Mel says:

    I think it’s important to remember that the article is not demonizing RUNNING at all. The problem is extended periods of time at an elevated heart rate that’s more than 65% of maximum.

    For example, when I walk for an hour, my heart rate stays low (around 50% of my max). That’s steady-state but it’s not the “bad cardio” referenced in the article because it’s a low heart rate that’s not putting stress on my body. That doesn’t cause the same effect as when I run for an hour (which would push me up beyond 65% of my max).

    I would guess that if a very conditioned runner can keep his/her heartrate below 65% of max, they wouldn’t have the same issues as a less fit person like me. Make sense?

    • Deb says:

      I was wondering why walking is ok!?! I guess u want to be under 65%? I so want to do intervals but I still have 50 pounds to lose & worry about my “aging” joints! I have started weight lifting 3x’s a week & love feeling strong! I’m nervous about crossfire – love eating paleo – however since st Patrick’s day splurge have been terribly inconsistent with my food! Planning another whole30 to get my head back in the game but lately I have been so prone to binging! On ” crappy processed horrid foods”! I love ur blog & cookbook & all the great comments on here!!

      • Mel says:

        Walking for long duration is great because it’s (usually) a low heart rate. When I started doing CrossFit, I started ignoring all this heart rate stuff, but now that I’m special 🙂 I’m back with my heart rate monitor and paying attention to the numbers, in addition to how I feel. Because, honestly, I like the way I feel when I’m going all out — and that’s not so good for my body any more.

        When I walk “fast,” I can still only get my heart rate to about 50% of max, which is below the threshold of the worrisome “steady state cardio.” Having said that, I don’t imagine that I’ll ever do more than an hour-ish walk, even at low heart rate.

        • deb says:

          Thanks! I LOVE long walks on weekends – I suppose I should get my garmin out of my junk drawer & check where I’m at!

  • Tim says:

    Your thoughts on the C2 rower for women?

    • Mel says:

      The mode of movement isn’t as important as duration and heart rate… that is, these same rules apply to swimming, rowing, cycling, etc. Extended work at high heart rate can be problematic. Sprints/intervals with recovery is probably a better choice.

    • Jaime says:

      4 x 500m sprints with 2:00 (or full recovery) between each one is miserable, but fun. 🙂

  • Wendy says:

    I’m so glad you posted this today! I am bummed about not eating right for the last 5 weeks, and not being able to dial in the way I WANT to eat on a regular basis. And running totally came to mind…I could lost the 10lbs and totally eat what I want if I ran. So, thanks for the reminder. I like intervals, it’s fun. And while I do want to be able to run a solid mile and even a solid 5K at a moments notice. I don’t want to be a long distance runner.

  • Once again thank you, thank you, thank you! I have never enjoyed running for long periods, and it makes sense after reading this article. I much prefer walking and I like doing the intervals from time to time just to change things up. Thank you for sharing!

  • Carol Lovett says:

    I’m happy I never liked cardio 🙂 I do more of a “no sweat” workout. I do 5 minutes on a bike to warm up then I immediately switch to pilates and medicine ball workouts.

  • Suzi says:

    Oh, heck! No one needs to tell ME not to run long distances. Honey, I’d only be doing that if Leatherface or Freddy Kruger was chasing me! HA! Besides, I don’t have the body for running: bad ankles/knees and big b00bs. Not a good combo if you want to run without falling flat on your face. 😉

  • Mariah B says:

    I love the original article, your post, and you.. for being so honest. 🙂 I’m so thankful I found lifting instead of chronic cardio.

  • Stacey says:

    I can’t lie, this article made me feel pretty blue. I’ve been working out, yup, cardio, and not losing weight. I run three days a week and lift or HIIT two days. The problem is, I’m training for a half marathon and really enjoying it. I hate to think that I should abandon long cardio when this race is over, not because I believe it is the key to weight loss, but because I’ve been enjoying it. I guess I could just try to balance it more… intervals and only one long run each week?

  • Cynthia says:

    I knew there was something wrong caused by the intensive running phase of my life (in my late 20s). Coupled with ultra low fat Ornish style eating it was a disaster!

    Yeah no one has to tell me not to run.

    But the no cardio thing makes me a little sad. You see, I love to dance. And at least some of my dance-oriented activity is probably somewhat high-intensity (Zumba). I don’t do it for the cardio really, I do it for the stress reduction and the joyful movement and the room full of nice people all dancing together. Tell me it’s not killing my thyroid…dammit…

    • Mel says:

      I suspect the stress relief of Zumba outweighs the fact that you’re doing it for more than 20 minutes… and it’s not consistent high-intensity the whole time, right?

      • Cynthia says:

        I should probably check my heart rate more often. I did notice that when I got really zealous about Zumba when I first started it (going 5 times a week, probably) my weight did start to go up instead of down. I have been consciously dialing the intensity back a little.

  • Maggie C says:

    Umm…. this guy needs to get published but my history:
    SAD diet, junk food, shot up to 300lbs. at age 21
    Cut the junk, ate vegetarian, for a year, got to 250 by age 22
    Joined a gym at age 28 or so, got to 220 with some weights.
    Started running from age 30-37, cleaned up my diet tremendously (CW style! no fat, lotsa carbs) generally stayed within +/- 10 lbs of 210 that whole time while generally running 8-10 hours a week. Eating 1400 or so calories. Dress size (16-18) barely changed.
    Started primal at age 38. by age 39, down to 180, with very limited exercise, down to a size 12. Added HIIT/Crossfit 6 months ago, down to 173 and a size 10. Probably eat 1800 or so calories a day. Still work out less- maybe 3 hours a week.

  • Chris says:

    This is something I struggle with a ton. I get the stuff in the article and I’ve read others that are similar. Unfortunately, I still LOVE running. L.O.V.E. I feel powerful and strong when I run. I don’t enjoy weights at nearly the same level. I’ve toned down the running a ton a lot because, yes, my thyroid bonked several years ago (Hashimotos), but I still run. It’s like an addiction I tell you.

  • Suzi says:

    Oh – and although I’m personally not a runner (see my previous post) and this isn’t promoting long distance running, I just have to give a HUGE SHOUT OUT to all of the Boston Marathon runners who, after completing 26+ miles continued running another 2 miles to Mass General Hospital to donate blood after the bombings! WOOT! (Love that dirty water! Ohhhh- BOSTON YOU’RE MY HOME!)

  • Allison says:

    First, I totally feel you on having the LSD flashbacks (long slow distance, not the “other” kind 😉 My work schedule got bad for several months and thanks to lack of sleep and a less than optimal diet I’ve packed back on all the pounds I thought I had lost years ago. I definitely have the moments of insane panic when I think maybe I should just be cutting major calories, or running for hours. Thankfully I then have a moment of clarity and go down to my garage to throw around some weights. 🙂

    Second, I’ve seen this article floating around facebook and it’s great! Thanks for putting it up for more folks to see!

  • Whitney Gilles says:

    Mel, on the subject of lifting weights faster, do you apply that to the 5-3-1 programming? How quickly do you move through those lifts?

    • Mel says:

      I don’t ‘lift faster’ on my heavy lifts. The “lifts weights faster” philosophy is only applied to lighter weights — and you absolutely should not be trying to lift heavy weights with anything but alert, conscious, deliberate, slow movement.

      When Jen Sinkler says to lift faster, she’s referring to more “metcon” type workouts with kettlebells, light barbells, and dumbbells.

      Hope this makes sense.

  • karen says:

    Mel, what about Bodyrock or Daily HIIT??

    Are those workouts okay for a hypothyroid/PCOS girl??
    If not, what should I be doing???

    • Mel says:

      Hey, Karen!

      I’m no expert, so I can’t advise you on what you should or shouldn’t be doing. I shared this article because I think it makes good points at STEADY-STATE cardio and how it can potentially be problematic.

      I’m not familiar with the programs you mentioned, but my understanding is that real high-intensity workouts should be done 1-2 times per week maximum. But if you’re unsure, I recommend you talk to a trainer or naturopathic doctor who can help guide your program. Sadly, there are no hard and fast rules I can point you to — the “right” training program for you is based on YOUR particular hormone situation.

      Sorry I can’t be more specific for you!

  • NJ Paleo says:

    I have seen this article a few times. As a distance runner I have to say that there is probably some truth to it. I desperately love distance running and have found that when I keep my long easy runs SLOW I have better results all around. Speed is for HIIT days or for racing.

  • Justin says:

    Give that a read, it Examines all of Kiefers citations, lots of what he says is the exact opposite of what the studies prooved. Obviously cardio isn’t the best form of exercise for a change in body composition but it doesn’t make you hold onto fat or have long term effects on T3

  • Joanna says:

    As a graduate student, I can tell you that the number of citations has NO BEARING on the quality of the article. You must always be critical of how the author actually uses the citations.

    Always be critical of someone who says this is the absolute only truth. The only truth is that there is more to the story.

    As a steady-state runner with Hashimoto’s hypothyroidism, I’ll tell you that running has helped me lose weight and keep me healthy. But you need to find the right balance with your doctor.

    Also, this article disputes a lot of what Kiefer’s article does.

  • Sam Knox says:

    I’d just like to back-up what Justin and Joanna said.

    The original article is simply incorrect. None of the references support the idea that endurance training chronically lowers levels of T3, and at least two of them flatly contradict it. You’ve done your readers a real disservice.

    Low levels of T3 not related to primary hypothyroidism are caused by overtraining, undereating, or some combination of the two. Period.

    • Mel says:

      “You’ve done your readers a real disservice.”

      That’s pretty harsh. I’m learning along with everyone else, and I’ve NEVER claimed to be an expert. I share the things I come across that I think are interesting and potentially helpful. I think you can take issue with the original article without placing blame at my feet.

      If you have knowledge to share with us, perhaps you could do it without criticizing me first. We’re all trying to find the best information to take care of ourselves.

  • Krista says:

    Thank you for this article. I agree 100%. As a person that knows and reads ton about nutrition and exercise, it is hard to go from all cardio to HIIT. I turned hypo in Feb of this year and I can now see that I created this hell for my body. In 2013 I ran and ran and ran and ran, and I lost weight. I was down to 145 lbs and now back up 165. It is hard to not do just straight cardio at the gym b/c I know that I will lose the 20 lbs again but I also know the damage that happens to my body. It feels like a catch 22. Accepting my body for what it is and focusing on how strong I am now and how strong I can become. Thank you for putting my crazy ruminating thoughts into this article.

  • Casey says:

    I must be a paradox. I gained almost 70 pounds while doing CrossFit (and eventually switching to BodyRock HIIT at home) and eating paleo, after being a lean endurance cyclist all through my 20’s and early 30’s. I tried CF just to say I did it, loved it, and then did it for several years before my thyroid tanked and the weight rapidly came on. Then, one day I fell during a WOD and was injured. After taking a full year off all exercise, I slowly went back to riding my bike. The weight is now inching off now that I’m back to riding. Maybe it is because I train the way Mark Sisson suggests, keeping my heart rate in the cardio range.
    All I can say is HIIT did permanent damage to my body. I loved it, and anyone who can do it should, but it just was too much for me.