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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.

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  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.

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