Menu Close

Two Reasons Why the Ketogenic Diet Causes Insulin Resistance, Pre-Diabetes, or Diabetes

You probably know someone who has tried or is currently on the keto diet. It’s pretty tempting, right? Most people see some great results.  Weight loss. Higher energy levels. Maybe even a drop in fasting blood glucose and hemoglobin A1c (HgbA1c). HgbA1c is a simple blood test that gives a picture of how well an individual’s blood sugar levels are regulated in the past 2-3 months. The higher the levels, the greater the risk for diabetes or diabetes complications.

However, what’s missing from this equation is the long-term affect of the ketogenic diet. In the short-term, when someone whose body has a poor tolerance to sugar or glucose (including more nutrient-dense carbohydrates, like fruits and vegetables), the ketogenic diet appears to improve labs and values that indicate insulin resistance. Because we’re eliminating the “trigger” food, so to speak. But, we aren’t addressing the root cause of this poor carb tolerance. In the long-run, the ketogenic diet can actually cause insulin resistance, pre-diabetes, diabetes. Here’s two reasons why.

#1 – The Ketogenic Diet Induces an Emergency Response in the Body 

The ketogenic diet is a high fat diet. When followed 100% the diet requires an individual to consume 50 grams or less of carbohydrates on a daily basis. Often people talk about becoming “fat burners” and having to be on the ketogenic diet long enough to adapt to fat-burning. This is a complete misunderstanding. Humans are not designed to burn fat, except for when there is an emergency. So when we create an environment in which our body has to use a resource to make energy that it would otherwise only use in the case of an emergency, we purposely create an emergency situation in our body. 

Emergency situation = chronic exposure to stress hormones. 24 hours. 7 days a week. 365 days a year (if you last on the ketogenic diet that long). The entire purpose of these stress hormones is to increase access to energy for the body. What’s this energy? SUGAR. So, purposely inducing an emergency situation in the body leads to chronically high levels of sugar in the blood. Long-term excess sugar in the blood = insulin resistance. Pre-diabetes. Or even diabetes. 

Now, this high fat diet has taken an individual who already has issues with processing carbohydrates farther away from a metabolism that can process carbs well. Not even just poor tolerance of carbohydrates, but full blown insulin resistance. Now, when this individual reintroduces carbohydrates, they will experience immediate weight gain or other side effects of putting excess carbs in a body that doesn’t know how to process them very well.

#2 – The Body Cannot Burn Carbohydrates Well, if There’s Too Much Fat in the Diet

The name for this concept: the Randle Cycle. In the 1960s, Dr. Randle discovered that there is an inverse relationship between fat and carb burning. Essentially, when there is too much fat in the diet, as is the case for a ketogenic diet or the typical American diet, the body’s ability to burn the carbs we eat goes down. Which means that when we reintroduce carbs after a ketogenic diet, our body doesn’t know how to handle the carbohydrates. It’s pretty similar to a muscle – if you don’t use it, you lose it. A ketogenic diet dramatically reduces the body’s needs to burn carbs, which then stunts its ability to burn carbs when we do eat carbs. Which then leads to a poor tolerance of carbs and insulin resistance. It’s not just the ketogenic diet. Eating too much fat (>25% of your daily calories) also works in the same way. 

There you have it. Two reasons why a ketogenic/high-fat diet can lead to insulin resistance, pre-diabetes, or diabetes.

Check out my free guides on PCOS & hypothyroidism below. 



  1. L. Herren

    Oh wow, this actually happened to me. I lost a ton of weight on keto and after about a year I had my labs done and was prediabetic. Years later, now off keto, I’m still struggling to keep my blood sugar down even though I’ve made many improvements to my diet and lifestyle. The Best so far is going plant based no oil (labs went from bad to really amazing within six weeks), but the quarantine really did a number on my drive to make separate meals for myself and my family so I just eat what I make them. Slowly getting back to plant based though because if I falter and eat bad for any length of time my labs come back prediabetic. The good thing is I get them checked twice a year so I keep good tabs on it.

    • Nosheen

      Hi, so glad to hear you’ve transitioned off of keto and are implementing a more balanced food strategy! Making separate meals for oneself can be very challenging, for sure. Hopefully, in time, you’re able to find a good balance between enjoying what is made for the rest of the family and taking care of your health. =)

  2. Orlan Cote

    Hi. I have been on a ketogenic diet for almost 4 years. Around 25gr of carbs a day.
    Sometimes, I have a carb day. I’ll stuff myself on pizza or pastas.
    I tested my ketones levels 4 hours after the meal and they are much higher than on my usual keto diet.
    It seems if I eat large amounts of carbs, ketone bodies goe up.
    Am I insulin resistant ?

    • Nosheen

      It could indicate insulin resistance or even that you may not be producing enough insulin to deal with the amount of carbs you are consuming. I would encourage you to share this information with your doctor or even better, an endocrinologist.

    • Nosheen

      Hi Dawn,

      Yes! If you are just coming off keto, it’s important to reintroduce carbs very, very slowly. To address insulin resistance, focus on eating balanced meals, getting enough movement (i.e. walking and strength training), getting enough minerals, using supplements strategically, managing stress, etc.

  3. Fred

    Can you please show evidence regarding insulin resistance on keto? I’ve been in ketosis for over three years and I’m very interested but I need evidence. Also I need to know if it’s a permanent insulin resistance or if it’s just temporary. I need a randomized controlled study as evidence. Thank you!

    • Nosheen


      I don’t think there are any randomized controlled trials looking at the long-term affects of keto on the human body. My blog post is based on an understanding of biological processes in the body and understanding how keto impacts the body based on these processes. I don’t think keto would cause long-term insulin resistance; however, it will take time to get back to a point where you can consume a decent amount of carbs a day without it negatively impacting your blood sugar.

      Here’s a conclusion from a review article on keto:

      “Based on our review, within the first 6-12 months of initiating KD, transient decreases in blood pressure, triglycerides, and glycosylated hemoglobin, as well as increases in HDL and weight loss may be observed. However, the aforementioned effects are generally not seen after 12 months of therapy, as the changes reported in the studies we reviewed are not statistically significant. Further research is warranted to evaluate the long-term implications of KD. Despite the diet’s favorable effect on HDL-C, the concomitant increases in LDL-C and very-low-density lipoproteins (VLDL) may lead to increased cardiovascular risks. Additionally, the dietary restrictions required to sustain ketosis may actually lead to its low sustainability. Unfortunately, most available studies lack generalizability and validity due to their small sample sizes and short study durations. Due to the limited amount of robust studies and lack of strong evidence evaluating the diet’s potential risks, recommendations supporting VLCKD in patients with no comorbidities, or cardiometabolic and endocrinologic diseases should be made at the provider’s discretion.”

  4. S.

    This is very interesting to me as i was interested in keto because i personally know several people who were pre diabetic, had insulin resistance or pcos or a combination of the aforementioned and they are actually thriving now after keto. Some had other issues like asthma and other allergies and they disappeared after their weight loss as well. They are all in the maintenance phase now which most hope to stay in for pretty much forever as they say they feel best that way. Any idea how that works?

    • Nosheen

      Hi! Thanks for your question. Keto can have positive, short-term impact on the body. There’s no denying that. But the body is not designed to survive without carbs. Basic biological functions depend on carbs. And whether we eat them in our diet or not, the body will make carbs by burning fat and breaking down muscle and organ tissue (protein).

      Some people may experience benefits in symptoms of asthma or allergies because carbs also feed gut bacteria. Poor gut health can contribute to asthma or allergies. Poor gut health is also common in women with PCOS. When we cut out carbs, it can improve poor gut health-related symptoms. The solution isn’t to cut out carbs though; it’s to improve gut health so you CAN digest carbs and promote the growth of good bacteria.

  5. Tony

    Hi Nosheen,

    Thank you for reading this post. I found your site after being shocked today after speaking with my GP. I am male, 49yo, Asian, with a diabetic T2 condition. I started keto approx 3 months ago with good committed behavior. My starting weight was 212lbs and I am at 198lbs currently. It felt great to eat less than 25g carbs a day and I lost my intense carb cravings. The weight loss was motivating and reinforced the commitment to the diet portion. Exercise was on the lower side. I took my blood tests and the panel came back at an HbA1C of 7.7! I haven’t had sugar or carbs over an amount of 25g/daily in three months. I just couldn’t figure it out. I was expecting a stellar A1C level after 3 months of no sweets, pastas, refined bread, cakes. I feel so perplexed because I have been feeling physically better, but seeing my glucose that high has disheartened my outlook on my health progress despite losing weight. I thought I would have had more normalized levels of blood glucose. I now don’t know what to do regarding my diet. Do I need to (slowly) re-integrate carbs into my diet and workout more? Are there other major changes to my diet I should consider?

    • Nosheen


      Thanks so much for your comment! Yes, I’d encourage you to VERY slowly reintroduce carbs. It would be best to start with more quantities of lower-carb fruits/veggies. And then slowly introduce slightly higher-carb fruits and veggies. Then eventually progress to starches and grains. It will take time for your body’s metabolism to come back up enough to burn the carbs as fuel. So as best as you can, commit to going slowly.

      Keto makes it harder to meet all your vitamin and mineral needs, which could have also contributed to the poor blood sugar regulation. And not to mention the immense amount of physical/physiological stress the body goes through on a keto diet, which naturally raises blood sugar. You can read more about that here:

      If you’d like more one-on-one support in bringing down your A1c while eating carbs, please feel free to reach out! You can schedule a free information call here:

  6. Hege Lianne Williams

    Hi! I suspected this, and I’m so glad I found your post.

    Always a slim girl, with a suuuper metabolism, I started gaining weight after taking SSRI. Thought keto was the solution. Lost a lot of weight. Came off keto. Gained back 3 x the weight lost.

    Now I swear I gain weight just by LOOKING at carbs 🙁

    My metabolism is gone with a capital g. Do you have any tips on how to restart my metabolism, so at least I can tolerate normal amount of carbs again? Without gaining 10lbs every time I want to have a banana?

    • Nosheen

      Hi Hege,

      I’m so sorry to hear about your struggles with weight and intolerance to carbs. I’d have to learn more about your specific situation to give you some tailored advice; however, I think the best place to start is VERY slowly and with low-carb veggies and fruits, like carrots, green beans, lettuce, eggplant, berries, etc. The body needs time to be able to adjust to burning carbs again. I would also encourage you to get checked for insulin resistance by asking your doctor to check your HgbA1c, fasting blood glucose, and insulin levels. It might also be worth it to get your thyroid checked.

      I hope that helps!

  7. Carole

    So glad to find this article. I have lost 20 pounds on the keto diet. Today I had a blood test with poor A1c numbers that said I am pre diabetic. Keto was all I could think of as a cause as I exercise, rarely eat sugar, and am not overweight. Now, I am looking for ways to lower my A1c. Any help you can provide would be appreciated.

Leave a Reply

Your email address will not be published. Required fields are marked *