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27 Aug

Dear Mark: Does Eating a Low Carb Diet Cause Insulin Resistance?

Despite all the success you might have had with the Primal way of life, doubts can still nag at you. Maybe it’s something you read, or something someone said to you, or a disapproving glance or offhand comment from a person you otherwise respect, but it’s pretty common when you’re doing something, like giving up grains, avoiding processed food, or eating animal fat, that challenges deeply-and-widely held beliefs about health and wellness. It doesn’t really even matter that you’re losing weight or seem to be thriving; you may still have questions. That’s healthy and smart, and it’s totally natural.

A question I’ve been getting of late is the effect of reducing carb intake on insulin sensitivity. It’s often bandied about that going low carb is good for folks with insulin resistance, but it’s also said that low carb can worsen insulin resistance. Are both true and, if so, how do they all jibe together? That’s what the reader was wondering with this week’s question:

Hi Mark,

I’ve been Primal for a few months now and love it. Lowering my carbs and upping my animal fat helped me lose weight and gain tons of energy (not too shabby for a middle-aged guy!). However, I’m a little worried. I’ve heard that low carb diets can increase insulin resistance. Even though I’ve done well and feel great, should I be worried about insulin resistance? Do I need to increase my carb intake? I always thought low carb Primal was supposed to improve insulin function.


Going Primal usually does improve insulin sensitivity, both directly and in a roundabout way. It improves directly because you lose weight, you reduce your intake of inflammatory foods, you lower systemic inflammation (by getting some sun, smart exercise, omega-3s, and reducing or dealing with stress), and you eat a wide variety of plants, animals, and herbs with anti-inflammatory and/or insulin-sensitizing effects. It improves indirectly because you are removing the thing that exacerbates the condition – large amounts of carbohydrates – and thus avoiding the negative effects. You might still be insulin resistant, but since you aren’t cramming your face with carbs anymore, you don’t notice it.

And sure enough, the weight loss studies indicate that during weight loss, very low carb diets improve insulin sensitivity:

However, going very low carb – to around or below 10% of calories, or full-blown ketogenic – can induce “physiological” insulin resistance. Physiological insulin resistance is an adaptation, a normal biological reaction to a lack of dietary glucose. As I’ve said in the past, the brain must have glucose. It can use ketones and lactate quite effectively, thus reducing the glucose requirement, but at the end of the day it still requires a portion of glucose. Now, in a low-glucose state, where the body senses that dietary glucose might not be coming anytime soon, peripheral insulin resistance is triggered. This prevents the muscles from taking up “precious” glucose that the brain requires. The brain’s sensitivity to insulin is preserved, allowing it to grab what glucose it needs from the paltry – but sufficient – levels available to it.

It appears that weight loss is the deciding factor, and since low carb diets tend to be more effective at inducing weight loss in subjects, they also tend to be better at reducing insulin resistance in insulin-resistant, overweight people. Once you’re lean and weight stable, though, very low carb diets (less than 10% of calories from carbs) can reduce insulin sensitivity. This is normal and totally necessary in the context of a very low carb diet. If we didn’t become insulin resistant while eating very low carb, our brain wouldn’t be able to get the glucose it needed to keep us alive.

Okay, but what about dietary amino acids? If our tissues are insulin resistant on very low carb, and insulin also promotes muscle protein synthesis, doesn’t that mean the amino acids from the protein we eat have a harder time getting into our muscles? You might think that, but that’s not how it plays out in the real world. In actual clinical trials, low carb diets are consistently linked with preservation of lean mass during weight loss. People on low carb diets lose more fat and less lean mass.

Muscle glycogen stores may be depleted, but if you want to fill those back up, you can do so quite effectively post workout, even when you’re low carb and otherwise physiologically insulin resistant. A bout of weight lifting, sprints, or even just regular walking can improve your ability to tolerate and handle glucose by making you more insulin-sensitive. This holds true even for the otherwise insulin-resistant.

In the end, insulin resistance on very low carb appears to be a physiological adaptation to spare glucose for the brain and prevent your muscles from gobbling it up. I see no reason to think it’s a pathological problem, especially given the droves of success stories on this site and others from people who have lost weight, torn up prescriptions, boggled the minds of doctors, and reclaimed their once-failing health through a low-carb Primal way of eating and living. I could be wrong, and time will tell, I suppose, but I doubt it.

Besides, there are far more pressing potentially negative influences on insulin sensitivity that we can be addressing, like:

  • Sedentary lifestyles. And I’m not just talking about strength training and high-intensity sprints; simple, basic low-level physical activity, like walking on a daily basis, can have a powerful effect on insulin resistance.
  • Unchecked and out-of-control appetites. Weight gain and an excess of energy (that the mitochondria can’t handle for whatever reason) are potent causes of insulin resistance.
  • Environmental pollutants and toxins like BPA and various fungicides can have negative effects on insulin sensitivity.

To sum up, I don’t think you need to worry about insulin resistance as long as you’re still losing weight – which you appear to be doing – since weight loss exerts a powerful effect on insulin sensitivity. However, once you’re lean, or have stalled without changing anything, moving back toward the 100-150 Primal carb gram range will keep your insulin receptors “honest” without causing weight gain (and it may even jumpstart weight loss again). Lifting heavy things, sprinting every once in awhile (in a manner suitable for your physical limitations), and doing lots of slow moving will also keep you insulin-sensitive, particularly after the physical activity.

Thanks for reading, folks, and I hope I cleared this up for you without raising too many more questions. Let me know your experience in the comment section.

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. If I eat around 50g of Carbs a day am I allowed one or two beers a day? Please? :-)

    Chris wrote on September 6th, 2012
  2. Interesting article… starting to make sense. I went primal about a year ago. I went really low carb. Didn’t lose ANY weight. Then, as soon as I added carbs back in, I gained 50 pounds just as quick as anything. I’ve been going to the Doc. Tests say my glucose is spot on, but I have all the symptoms of PCOS. The symptoms all stem from glucose resistance.
    This article explains what has happened to me. I was really confused how I could become glucose resistant after eating such a low carb diet.

    Laura wrote on September 9th, 2012
  3. I do Leangains and carb cycle. The 100-150 grams of carbs on the curve is ridiculous and has no scientific basis. I do 35 grams of carbs on rest days and 270-ish on training days and I’m lean. Eating too much fat, too much carbs or too much protein will make you fat, not good carbs for active people.

    No, I’m not a sugar burner. I burn fat and glucose like all people.

    Kate wrote on September 14th, 2012
    • This will greatly depend on what you do on your training days. Do you do crossfit type workouts that burn glycogen/glucose? Then yes, carbs are necessary. I’m assuming at 270g of carbs on training days means you’re doing some intense stuff. Whatever the case, it’s working for you so keep doing it! 😉

      JPizzay wrote on September 14th, 2012
  4. The 100-150 amount is meant for maintenance and doesn’t include an activity factor.

    He says in his posts that if you are more active having more carbohydrates works.

    It is not necessary though.

    Read The Art and Science of Low Carbohydrate Living/Performance for more details

    Sure you can do just fine on carb cycling, but I don’t think its at all necessary.

    Jonathan Swaringen wrote on September 14th, 2012
  5. High insulin sensitivity ensures that the body responds to minimal levels of insulin and is able to successfully maintain blood glucose levels in the normal range. Decreased insulin sensitivity could result in hyperinsulinemia and hyperglycemia. The excess insulin in the blood stream can damage the blood vessels, increase risk of heart disease, blood pressure, obesity accelerated ageing and even cancer. The most universal cause of insulin resistance is believed to be aging but other lifestyle factors such as poor dietary habits and lack of physical activity also play a role. The good news is that you can improve insulin sensitivity by adopting specific measures associated with diet and exercise. Here’s how

    Brian Walpole wrote on November 12th, 2012
  6. I found that eating small “mini meals” made me insulin resistant. When I switched over to eating 2 meals a day, the weight cam off quite nicely.

    Laura wrote on November 24th, 2012
  7. Dear Mark, do you know what levels of fasting insulin are involved with so called “physiological insulin resistance” ?
    In this study below the low carb group dropped fasting insulin from 10.7 to 7.1 over 12 wks with 4% carbs.
    Is the mentioned effect coming showing up at 10, 7.5, 5 mU/L or lower? Have anything at the lower levels shown any harmful effects, or is it mere redirections to critical organs at very low calorie intake? Looking fwd to your reply. Also what ketone levels were involved?
    If you can include a link to the study that showed the insulin resistance response, my question about the levels would easily be clarified!

    sten bj wrote on January 6th, 2013
  8. Very interesting article.
    I always heard people saying that low carbohydrate diet can cause insulin resistance but i never really believed them. After reading your article, it makes much more sense.
    Thanks for sharing and contributing to the knowledge.

    Chris wrote on July 25th, 2013
  9. If low-carb causes or increases insulin resistance, how does a type-2 diabetic benefit from it? We know that they do benefit from it, but I don’t understand how a type-2 diabetic’s insulin resistance can decrease using a diet that causes insulin resistance.

    Bob Smith wrote on August 9th, 2013
    • I am ONLY speaking at as type 2, not someone with medical knowledge.
      I found this page when I read elsewhere that low carb leads to insulin resistance, and it worried me because I have been low carb for just under a year and a half.

      This article makes me feel a bit better. I was worried that it was a matter of time before low carb fails me and I have to worry about taking meds.

      It has worked for me, and I believe that it has improved my insulin sensitivity.

      I say this because I was diagnosed with a blood glucose of over 230 several hours after eating. A1C was about 8. After low carb, my fasting bg is usually in the 80’s and my 3 A1c’s since diagnosis have been 4.8, 5.2 and 5.1.

      Since I eat low carb and rarely go over 50g, I would not expect it to go much higher than 110, so I did a test after christmas 2013. I had 2 small lemon cupcakes, and tested my blood before and a few times after. My BG went up to 151, which is higher than I had seen in nearly a year, but it went down back to the low 90’s within 2 hours and to 80’s a little after that. Prior to low carb, it would have gone higher and stayed there longer.

      This is anecdotal, and still not long term yet, but just to show that at least with this individual type 2, low carb has helped in all ways I can check. BG normal, blood pressure normal, lost 80 lbs so far, lipid panel is excellent. (Was OK before, but HDL was low, but now they are much higher)

      Linda wrote on February 25th, 2014
      • Forgot to add, I also had my thyroid removed 30 years ago (cancer) as a kid, so even with that complication, low carb is helping me finally lose weight without hunger or stress. And my levothyroxine went from 225mcg to now 137mcg. And I have energy, which has been lacking for years.

        Linda wrote on February 25th, 2014
  10. i am so confused. i have been on a very low carbohydrate diet for years (2-3) without any weight loss to speak of (my mother and best friend have lost 30-50 plus pounds eating the same things). i am 43, 189 pounds, 5’6. should be thirty pounds less. i have been trying the high fat, low carb, ketogenic diet (about 85/15/5} around 60 or so grams of protein. pastured meats, raw dairy, very quality foods. super health conscious. cannot lose weight to save my life. now i my fasting blood glucose (after at least 12 hours of no food whatsoever) is almost always over 90. i wish someone could help me!!! i am otherwise healthy but so sick of having a fat gut. am i insulin resistant? if so, how can i change? i have a very healthy lifestyle as far as i can tell……but tired often, not energetic…… coconut oil, etc. take some supplements, grass fed, pastured, organic, raw….all that! any ideas???? thank you so much for your time :)

    aimee wrote on September 7th, 2013
    • Aimee,
      Could it be that you may not be getting exercise? Walking would surely help, such as walking about an hour a day on the treadmill or outdoors, but possibly you are already doing this? Another long-shot problem could be related to a gut flora issue. Maybe Mark would have a suggestion or two with possible methods that may help identify the independent variable that’s getting in the way of your inability to lose the additional weight.
      Best Regards,
      Dave P.

      Dave P wrote on September 8th, 2013
    • You might have non-diet related issues, prob worth speaking to a knowledgeable doctor :)

      Elizabeth wrote on September 8th, 2013
  11. I know this thread is old, but if anyone could hook me up with some insight that would be awesome! I had a fasting blood sugar of 109 about a year ago and started getting symptoms of PCOS, mainly thinning hair. My DHEA was a bit elevated as well. I am thin, 98 pounds and 5’2. I began and paleo diet (already ate GF and DF) but cut out a lot fruit, grains, and white potatoes. Digestively I feel great, but Since going so low carb (around 30 grams a day) I am constantly hungry and have moments of hypoglycemia like symptoms. I have in the last few days started eating more carbs and the symptoms have worsened. Any insight or advice? Thanks!

    christina pann wrote on February 17th, 2014
    • Eat more fats.

      Brandi wrote on September 29th, 2014
  12. good carbs make you insulin sensitive. Eating lots of protein and fat cause insulin resistance. This has been well studied. you can tell yourself whatever you want. It doesn’t change the facts. Loading omega 3’s is one way to mitigate such poor diet advice. Just because you lose weight does not tell you what is happening. Get your blood work done and stop reading partial information from people talking out their asses.

    Steve wrote on September 23rd, 2014
    • Fat is the only macro nutrient that does not trigger insulin, so I am not sure you’ve read any of the studies on this. It is a well known fact that constant bombardment of carbohydrates and excessive amounts of protein cause a decline in sensitivity. Over many years carbs like sugar(yes even fruits), starch, and grains constantly raising your blood sugar so often your body no longer recognizes insulin and then you begin to produce more and more insulin to do the same thing it had no problem doing earlier. Eventually due to ever increasing pressure to lower your glucose damages the beta cells in your pancreas and your pancreas can no longer produce enough insulin to bring it down and a type two diabetic will then need to start taking insulin injections. This is my mother current condition. ‘Good’ carbs won’t make you sensitive to the effects of insulin, on the contrary for those who are already metabolically challenged (me) it’s makes it worse. I had a facepalm reaction to your ignorance(or misstated?), fat emphatically does not increase insulin resistance(nor does it make you fat, science says so), learn your science not regurgitate politically correct CW.

      Brandi wrote on September 29th, 2014
      • My son has type 1 diabetes. After his “honeymoon period” where his pancreas was still helping he started to need much more insulin because of the high fat content of his diet. (He himself is very lean with a very low-too low BMI). Anyway the fat enters the bloodstream over several hours and makes you less sentitive to your insulin by filling up muscle cells and also surrounding them with fat. As a result, in his case, his basal insulin became insufficient many hours after a high fat meal and his blood sugar rose. He typically would be “in range” for 2-3 hours after a meal with high fat and then spike high 3-4.5 hours after eating. I believed firmly in 100-150 (or 20-30%) carbs and it workd great for him until he became insulin resistant from all of the intra and intermuscular fat in and around his muscles. This supresses the synthesis of glycolytic enzymes in muscles as they prefer to burn fat and so synthesize more enzymes that are responsible for beta oxidation of fat. He now needs double the amount of insulin per gram of carbs as most kids his size (on about half the carbs) so it ended up being a net wash in that regard.

        Joe Hirsch wrote on February 15th, 2016
  13. I have been (mostly) paleo for about 3 years. Because I have PCOS, my MD suggested insulin resistance testing. Because my diet is already lower carb, would I still test positive on the insulin resistance test? Hope my question makes sense!

    Katherine wrote on September 27th, 2014
  14. How do you over come this? I got into a ketogenic state within 2 weeks of starting a keto diet, my blood sugars turned around and became quite excellent regularly maintaining in the 80s and I lost 16lbs. I have not changed what I’ve eaten yet now I cannot get my blood sugars under 100. Which naturally is preventing ketones and weight loss. I understand that this ‘problem’ not only assists the brain with its glucose requirements but also protects the muscles.

    Would lifting weights or doing body weight exercises help the muscles become more insulin sensitive and help bring down those blood sugars? Or make it worse?

    Should I raise my carbs in an attempt to turn it off? Then return to ketosis?

    I am not finding any answers, mostly because studies are not focused on real ketosis diets or real low carb diets. All low carb diets studies are way to high carbs and not removing grains, ie useless. They label them bad without looking further and it’s quite aggravating but they keep doing study after study on low fat calorie restrictive diets. I need to know the pathway this physiological insulin resistance can be alleviated by not simply ‘get off keto’ recommendation.

    Brandi wrote on September 29th, 2014
  15. Lifting heavy things will turn around physiological insulin resistance. . . Btw is NOT the same as regular insulin resistance, it wont ruin you pancreas and whatnot. Repeat, its not regular insulin resistance its just a defence mechanism, LIFT HEAVY THINGS you blood sugar will come down and you will lose weight.

    Brandi wrote on September 30th, 2014
  16. hello Mark,

    There were no references/links to any scientific papers for your statement:

    “However, going very low carb – to around or below 10% of calories, or full-blown ketogenic – can induce “physiological” insulin resistance.”

    Do you have any? I read this paper, but its results did not show reduced glucose disposal under euglycemic clamp after exogenous insulin for a very low carb diet compared to a high carb diet (i.e., did not show increased insulin resistance of peripheral tissues).

    I would be fascinated to know if you have found a study which did show reduced glucose uptake by peripheral tissues after a low carb diet compared to a higher carb diet. If not, though, what was the basis for your statement?

    Eric wrote on November 9th, 2014
  17. Hi mates, how is the whole thing, and what you
    would like to say concerning this post, in my view its actually awesome in favor of me.

    Isidra wrote on February 3rd, 2015
  18. In conclusion? High level of glucose in LC raise insuline level too?

    Garrafa wrote on May 16th, 2015
  19. Great article! however, I am underweight and have diabetes (31 y/o female with A1c 6.6 (diet controlled) and 92 lb and 5’5″. I have lost about 30 lbs since last year when I started eating low carb diet. Now I am trying to gain weight by adding some complex carbs (now at 100 grams per day). This increases my blood sugars (fasting and post meals) and actually increased my A1C too (6.4 to 6.6). My fasting sugars were lower when i was eating regular carb diet before weight loss. One of my doctors was thinking that because i dont have any muscle mass left, sugars have no where to go, can this be true? What should I do at this time? Thank you!!

    sarah wrote on August 5th, 2015
  20. Thanks for the very straightforward post.

    The question niggles: Why do those cells shut their doors? Isn’t it sensible to get to the bottom of the biochemical mechanism to understand it better?

    goawaybird wrote on August 22nd, 2015
  21. I know I’m late to this party but I have a conundrum. I’m a 33 yo female, 5’3″ and 145# – I have 10# of baby weight to lose, but had been pretty steady at 135 for quite awhile other than pregnancies. I eat about 70% clean, 30% (wine + sugar are my weaknesses.)

    I’ve only had blood glucose issues when I’m eating clean… what gives?
    Example 1: I was doing a W30 while pregnant, and when I did the glucose drink thing, I registered off the charts high. At the follow up test, you basically have to binge on carbs for 3 days, and after that I passed with flying colors.
    Example 2: I had a carb-y birthday celebration over the weekend, and thus made sure to eat pretty clean during the week (eggs, fish, veggies, a bit of farro salad and milk). I ended up snacking on a fruit snack packet and got a massive headache and brain fog. The next day I had a biometric screening and my fasting level (12 hr fast) was 108. What gives? It’s almost like eating clean makes my body forget what to do with sugar! I’ve only had these diabetic/pre-diabetic numbers after cutting out junk, and it’s really confusing/disheartening. Would appreciate any insight!

    Erica wrote on September 3rd, 2015
  22. So… my carbs hover around 50-80 g/day. However, I do CrossFit. I’m a young, muscular male to boot. So that’s pretty low. My glucose readings have been wonky lately. Assuming that’s due to insulin resistance caused by a low-carbohydrate diet, is it okay for my glucose to CONSTANTLY be 95-115 mg/dL? I want 70-80!

    Jacob Seymour wrote on December 11th, 2015
  23. I really need some help understanding this.
    My husband and I both a cried out the same test.
    We had our blood works done before starting the paleo diet.
    We did the paleo diet for 3 months.
    We both felt terrific, full of energy (didn’t sleep as well but we felt ok with that), no brain fog, great.
    We did the blood works again after the 3 months and were horrified (and a little pissed) that our bad cholesterol had shot up.
    And here’s the thing that I really need clearance on… I went from having a really low sugar level to a big one! This was not good news on either count.
    Both husband and I are slim, we live by the ocean, we practice yoga… Very healthy.
    My GP said that if you miss out an entire food group (grains) then your metabolism goes out of whack and that was the reason for the high sugar levels.
    Any advice would be appreciated.

    Vivien wrote on May 6th, 2016

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