Remembering Kevin Moore

Do Low-Carb Diets Lower Thyroid Function? Let’s Ask The Experts!


If you’ve been paying attention in the low-carb and/or Paleo communities over the past year or so, then no doubt you’ve heard the popular meme promoted by certain Paleo diet advocates that zero-carb and very low-carb diets (ketogenic) lead to lower thyroid function, among other issues. They claim that this leads to a diminished capacity for T4 to be converted into T3 thyroid hormone because of the lack of glucose consumed by low-carb dieters. This concept has been heavily promoted by highly-respected practioners like Chris Kresser who sees patients from what he describes as “the dark side of Paleo and low-carb” dealing with hair loss, cold extremities, feeling horrible and other such negative manifestations of experiencing a low thyroid function.

However, two of the top low-carb nutritional health researchers in the world — Dr. Stephen Phinney and Dr. Jeff Volek — say this phenomenon with low thyroid while on a low-carbohydrate diet promoted by people in the Paleo community like Kresser and Paul Jaminet is “a myth” and has not manifested itself in any of the research subjects in their numerous studies of people who are properly following a well-formulated low-carb diet with adequate calories over the past three decades. Dr. Phinney believes the primary point of contention revolves around consuming an adequate amount of calories with your low-carbohydrate nutritional intake in order to normalize thyroid and metabolic function without the necessity for consuming added sources of dietary glucose. Dr. Volek concurs stating that it’s calorie-restriction that brings on this low thyroid effect, not limiting carbohydrates.

The audio footage in this 20-minute video comes from excerpts of interviews that aired in 2012 on my brand new podcast called “Ask The Low-Carb Experts” podcast and you can hear the three interviews from these experts in their entirety by clicking on the links below.

Chris Kresser – All Things Thyroid (Thyroid 101) – Episode 10

Dr. Stephen Phinney – Long-Term Stalls & Weight Gain Even On A Well-Formulated Low-Carb Diet – Episode 23

Dr. Jeff Volek – Saturated Fat Is Good For You? – Episode 11

Your comments are welcomed and encouraged, so feel free to share your thoughts about what each of these experts shared. Do you think Kresser is right that it is low-carb diets that tend to lower thyroid function (from the lack of glucose necessary to convert T4 into T3) requiring these nutritional approaches to be avoided by many people? Or do you agree with Phinney and Volek who say it’s calorie-restriction, not carbohydrate-restriction that leads to these thyroid concerns? And if there are those, as Kresser notes, who can become adapted to eating a very low-carb diet without these negative effects on their thyroid function, shouldn’t we be attempting to find out what those people are doing differently (i.e. eating more calories than those who have problems) rather than pointing the finger of blame at this nutritional approach? What say YOU?

  • Kevin

    Verrrrrry interesting discussion! I’m dealing with this myself… and in my experience, it seems to come more from low cal then low carb. If I eat VLC or even keto, but try eat more than usual, I feel better. The hard part there is trying to eat more… because I just don’t want to! :) If I try to eat more carbs (rather than bumping up fat), I tend to feel worse. Even twitchy & grouchy sometimes. That hard part there is that I want to keep eating more & more carbs. And then I tend get twitchier & grouchier.

    • LLVLCBlog

      So you only seem to have these symptoms eating low-calorie and not necessarily eating low-carb? That’s in line with what Volek/Phinney have seen.

      • melancholyaeon

        Absolutely agree. On the Atkins Community, you’ll see the people who complain of this are low cal, they often aren’t tracking daily every meal. As a result they aren’t getting enough fat, and so are consistently under-eating, which is very easy if you’re in ketosis. Trying to live on 800-1000 cals a day will quickly crash almost everyone’s systems. If you hover at 1000-1200 you can get by for a longer time before the strain shows on your body. Women who are low-carbing need to eat at least 1500 cals a day unless you very very petite, in which case you should ensure you get 1300-1400. Men who are low-carbing should get at least 1800 a day, again unless they are quite short, in which case they should ensure they are getting at least 1700. It’s hard because so many people have been taught to starve themselves and it takes them time to re-adjust to normal portions. Not super-size, but just normal.

        • LLVLCBlog

          This may explain why Kresser sees so many patients dealing with this phenomenon because they’re stuck in diet mode cutting calories down too low. So it’s the calorie restriction not the carbohydrate restriction leading to this it seems.

          • Willis Morse

            That may well be. This whole thing with the ketone meter (thanks, Jimmy!) has finally forced me to track my food a lot, and I realized two things that I never would have guessed: I must eat half as much protein as I used to go to get into ketosis, and I’ve been eating about 1000 calories per day on average for the last couple of years and wondering why I feel like crap. It wasn’t intentional, I just don’t want to eat much. Every once in a while I would “binge” and then feel better the next day. I logged a typical binge the other day and found it was about 1900 calories. I have no idea how to eat that much more just in fat, though, short of chugging glasses of olive oil and eating sticks of butter.

            • LLVLCBlog

              No sense in “chugging” fat as long as you are putting it on everything you consume. Keep in mind there are 9 calories per gram of fat compared with 4 calories per gram of carbohydrate and protein. It doesn’t take GOBS of fat to get what you need. :)

  • Yes. I place patients on low carbohydrate diets and lower their thyroid function normalizes all the time.

    • LLVLCBlog

      And it’s likely because you feed your patients adequate calories when you put them on low-carbohydrate diets. Would you agree?

      • The low thyroid problem while on a Low-carb diet is a myth. Those patient’s who are having fatigue and hair loss issues are more than likely deficient in their Omega 3 to Omega 6 ratios and are not adequately replacing them in their diets. The thyroid axis corrects itself with a low carbohydrate diet as long as adequate Omega 3:6 fatty acids are consumed. Two good studies reveal a relationship with TSH to HDL in the last 5 years. Many low carbers may not be replaceing the Omega 3 fatty acids correctly and may be getting poor quality Omega 6 fatty acids. Just taking a fish oil capsule doesn’t always do it. The symptoms of hair loss, cold extremities, feeling horrible that Kesser implies are easily corrected by using adequate amounts of flax seed and olive oils or Udo’s oil. Many low carbers are affraid to increase their fat intake and may experience these symptoms due to caloric deficiency as well.
        About 30 % of the patient that I see with insulin resistance, metabolic syndrome or diabetes can be classified as subcliniclaly hypothyroid or hypothyroid due to a low T4 and or high TSH. This self corrects as long as adequate fat is replaced in the diet and carbohydrate is restricted. Calories do play a significant role, but when they are sufficient, correcting the Omega 3 to Omega 6 ratios are the key.

        • LLVLCBlog

          Another interesting piece to this puzzle, Adam. THANK YOU!

        • kevin

          Curious why the Omega 3:6 ratio is fixed with plant oils. How about animal fats, coconut oil … etc? Sounds interesting and I’d like to hear/read more on this.

          • Omega 6 & 3 ratio is fixed with plant oils because the body can’t make them so they must be supplied by diet. ONLY Omega 6 & 3 are essential fats since omega-6 linoleic acid & omega-3 alpha linoleic acids are the parent, or base substrates for the body’s production of essential local acting-cellular level hormones known as eicosanoids, i.e. leukotrenes, lipoxins, thromboxins and prostaglandins. The body can synthesize Omega 7 palmitic & vaccenic acids & Omega 9 oleic acid (olive oil) and so they are not essential, and Omega 7 & 9 and saturated fats are not used in the eicosanoid production pathway because they do not contain omega-6 linoleic acid or omega-3 alpha linoleic acids.

            For more see the Wikipedia page re Fatty Acid.

  • LLVLCBlog

    THANKS for sharing your story, Kevin! It does seem that cutting calories too low regardless of where you make those cuts (carbs, fat or protein) leads to what Kresser describes with the poor conversion of T4 to T3. But on my nutritional ketosis experiment, I’m making sure that although I’m on a very low-carb (3% of calories), very high-fat (85% of calories) I’m also eating enough calories. It can be a little challenging because nutritional ketosis makes you feel so satisfied you don’t necessarily want to eat. But my calories never dip into the level where these thyroid issues would manifest themselves. If my hands start getting cold, then I know I probably need to eat a little more for that day. It’s amazing how the body will give you these cues to know precisely what to eat and when.

  • I’ve experienced “feeling hypothyroid”, e.g. cold, dry skin, hair loss, brittle nails, a few times on different diets. Each time, eating low-calorie (around 1,200 or less) was the common denominator. It last occurred a few months ago when I was super low-carb; adding fat, coconut oil and heavy cream, fixed my symptoms in a few days.

    • LLVLCBlog

      And getting ample calories seems to mitigate that response.

  • Cnico

    Hi Jimmy… Don’t know if you remember me, but I was the one who posted about a year ago that weight loss for some people is not just about “low-carb”… that there are other factors. I went low-carb after my mom died, ate 1200 cal a day, was never hungry, had hypothyroid symptoms… went to the Holtorf Med Group in CA and was put on compounded T3 (time release), plus bioidentical hormones plus adrenal support… all three hormonal systems were out of whack. I did finally begin losing weight, eating about the same. During the same time, my project as a consulting scientist ended suddenly, I sold my house and moved to Mexico! I continued to lose a little bit of weight, but things have stabilized now.

    So this info is very helpful to me… initially I was eating a lot of coconut oil and my fat content was about 70%… however, with all the chaos of the project ending, selling my house, chaotic downsizing… I forgot about this part. So I am really glad for this podcast and this info.

    I have two questions for you: How does leptin resistance figure into this scenario? Is your leptin high or low? Mine is high and my T4>T3 conversion is a problem. Remember Jack Kruse and his big leptin diet from last year where you were supposed to start off the day with 50-60 g of protein? Two contradictory approaches … maybe something you can ask one of the experts too.

    Also, what about the HCG diet which supposedly deals with leptin resistance by aiding your body in burning the right kind of fat (I believe it is brown fat)… people who lose weight with the HCG diet (low-calorie) do not gain it back… I know several people who’ve lost weight that way and they have NOT gained it back. Holtorf/Wightman (at the So Cal office) recommend the HCG diet and swear by it.

    I don’t know the percentage of fats/carbs/protein on the HCG diet… but will look into it.

    Just some thoughts rattling around in my mind… I know that “one size does not fit all”… and perhaps that’s why some people do well on the Kruse leptin plan and some do well on the HCG diet… it is all so very curious!

    Thanks very much to any answers you can provide!

    • LLVLCBlog

      Leptin levels normalize on a well-formulated low-carb, moderate protein, low-carb diet with adequate calories. I’m learning that a big bonus of protein is probably not a good idea. No fan of HCG because it’s a low-calorie low-carb plan. No thanks!

      • Cnico

        Did you edit out my reply Jimmy? Normally you post replies and comment on them quickly. I would really appreciate knowing where your statement about leptin normalizing came from… not trying to be snarky… really curious. I am a scientist and I am wondering if there is any science that you know of behind the statement. Thanks!

        • LLVLCBlog

          I don’t “edit out” anything. I’m happy to comment on your concerns. Dr. Stephen Phinney noted that with adequate calories on a well-formulated low-carb diet, leptin levels are fine in his study patients.

          • Cnico

            Thank you very much… my original reply from last night must have gotten lost. Did he note how long it took for the leptin to normalize? Gracias…

            • LLVLCBlog

              Varies from person to person.

  • SpaceVegetable

    Huh. Well, this explains a lot. I haven’t listened to the podcast yet, but just from these comments, it seems this may be the problem I’m having. I’ve been suffering the symptoms of hypothyroid, though my lab work comes back normal. I’ve been low-carbing for quite a while, but my calorie intake has been around 800-1000 calories and I have been unable to lose any weight. I’m thinking maybe I should try eating more to see what happens.

    On an different note, I just had some genetic analysis done as a result of a health study I’m participating in for rheumatoid arthritis and some of the other results relate to things like insulin resistance, hormone levels, cholesterol levels, and the effects of fat consumption on BMI. It’s kind of fascinating and goes a long way to explaining why one-size-fits-all doesn’t work for these diets. There seem to be quite a few genetic factors that contribute to how our bodies process what we eat and it goes beyond just inherited predispositions to diabetes or obesity. It would be pretty neat if everyone was able to get such an analysis and be able to more finely target their own genetic makeup in terms of their diet. I suspect that sort of things is a ways off yet, but it’s still quite intriguing.

  • LLVLCBlog

    I agree everyone is different. However, the studies that Kresser cites are ones with calorie restriction and low-carb diets. I would love to see a study comparing the effect of the T4 to T3 conversion issue with varying levels of calories. It seems as long as you don’t consume 1200 calories or less with your low-carb diet, you won’t see these negative effects. There’s no need to “refeed” with “good carbs” once you become keto-adapted and use fat for fuel. If that works for you, then go for it. But there no requirement to do that strategy for people fueling themselves with ketone bodies. I don’t doubt your experience on low-carb, Elisabeth, and I’m happy you found what’s right for you now. Perhaps you are right that those who experience these low thyroid issues tend to be susceptible to making them worse by cutting calories more.

  • AJ

    I started low carbing for general health reasons several years ago, and I kept track of the calories I ate. I kept eating about the same amount of calories (actually I ate more the first few months), about 65-70% of them from fat, 30-35% from proteins and less than 1% from carbs.
    I felt just fine, for a couple weeks. Then I started to get more and more tired, needed to take a nap or two during the day. I started to gain weight, 4-5 pounds a month. I started to lose hair. And so on.
    New medical check and looking at my old journals showed that I had slightly lowered thyroid function before my diet change, but I didn’t have any symptoms until after the change. My TSH and T4 were about the same as before. But my T3 dropped after the change.

    • LLVLCBlog

      How many calories were you eating when this happened?

      • AJ

        Around 2000-2500 kcal a day, more or less depending on my
        workout. I’m female by the way, 5′ 8″ tall and back then I weighed 130 lb. After going low carb, I also got noticeably weaker after each time at the gym,
        losing muscle mass and collecting more fat and water.

        I’m on T4 and T3 supplements now, and slowly getting better.

        • LLVLCBlog

          Interesting. I’d be fascinated to know hat your menus looked like and whether you had signs of thyroid issues prior to going low-carb. Thank you for sharing!

          • AJ

            Funny, I barely remember what I ate before… Lots of pasta, bread, rice, low fat dairy products, cheap meat (preferably lean). The usual stuff. And I sure had a sweet tooth, I loved chocolate…
            I didn’t notice any thyroid issues before. Perhaps my “IBS” might have been a symptom of slow metabolism, but this problem disappeared quickly after the change.

            • LLVLCBlog

              I wonder if your crappy diet prior to lw-carb on tributed in any way.

  • LLVLCBlog
    • Oh, I have lifted in a ketogenic state and felt awesome. My comment has to do with keeping hormone levels optimized both for fat loss and for muscle building, and avoiding the dead-ends that people often reach on a diet that keeps insulin levels at baseline.

      I work with powerlifters and fitness models, some of whom have had very undesireable experiences on an ultra-low-carb with no carb refeeds. Several hormones, including leptin and thyroid T3, are modulated by insulin (or lack thereof), and going for long periods in a ketogenic state has left some of them both leptin resistant and insulin resistant, to the point where their metabolisms don’t function the way they want them — i.e. they stop losing fat and stop gaining muscle, and it’s not because they’re doing something “wrong” according to the dictates of nutritional ketosis (as you call it).

      What helps in those situations is *punctuated* high-carb eating — not the gradual “adding them back in” strategy Atkins came up with, and definitely not the “up your carbs to 60-100g per day” strategy which has absolutely no advantage whatsoever.

      Jimmy, this is *totally* a Your Mileage May Vary situation. If YOU feel awesome on pure keto and are building the muscle you want and losing the fat you want, then that’s great. I’m not the dogmatic personality on this.

      I’m just saying, context is hugely important (as our friend the Caveman has said in another comment — and by the way, his “gold star” went to a guy, Skyler Tanner, who trained under my mentor, Kiefer).

      It’s important not to try to paint this situation as black and white, like “low carb diets don’t work!” or “you’re not eating enough fat!” It’s not that simple.

      • LLVLCBlog

        Nothing is ever simple. :)