There’s some confusion on whether or not a low carb or ketogenic diet will cause people to develop insulin resistance on keto diet after this study was published. (1)https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2903931/
Insulin Resistance on Keto – Should You Be Worried?
As far as insulin resistance (or insulin sensitivity, depending on which end of the problem you’re looking at) goes, the vast majority of Americans already have some level of insulin resistance and metabolic disease without being low carb or on a ketogenic diet.
The above research study was done on mice that were fed a “keto” chow high-fat and low carb diet for 8 weeks. The researchers found that these mice developed insulin resistance on a ketogenic diet during the study period.
I’m the first to point out that animal studies can be challenging to apply directly to humans. While in some cases, there may be overlap between how animal and human studies, I think in this case of determining if a ketogenic diet can cause pathological insulin resistance, we need to leave the animal research behind and look at human studies of the ketogenic diet.
In fact, studies show that taking someone that is overweight and also has some level of insulin resistance and putting them on a well-formulated low carb or ketogenic diet will usually result in weight loss and improvement of their insulin resistance. In fact, we should see these people with lower circulating levels of insulin as well. (2) https://link.springer.com/article/10.1007/s00125-004-1603-4
As the body has a lower carbohydrate load, less insulin is needed to shuttle that circulating glucose to the muscles, liver, and fat cells. The lower circulating insulin levels over time should make us more sensitive, not less sensitive to the effects of insulin.
So why are people worried about insulin resistance if they stay on a low-carb ketogenic diet? I’m going to argue that not all insulin resistance is bad and that in some cases, insulin resistance may have a benefit to the body.
Pathologic versus physiologic insulin resistance
We need to define and separate the type of insulin resistance that occurs in a metabolically unhealthy, overweight person versus a metabolically healthy and normal weigh person. The underlying causes of their insulin resistance is significantly different.
The overweight person with insulin resistance has a pathologic insulin resistance due to a significant metabolic and hormone dysfunction. Years of high carb and high-fat diets lead to insulin resistance, weight gain, and eventually, in most people, the development of diabetes.
Now let’s take that metabolically unhealthy person with insulin resistance and put them on a well-formulated low-carb ketogenic diet.
As they lose weight on a well-formulated low-carb ketogenic diet, they will also in many cases, at least significantly improve their insulin resistance, if not completely reverse the previous insulin resistance.
Now that we’ve helped turn that person into a normal weight, metabolically health individual, what happens if we keep them on a well-formulated low-carb ketogenic diet?
The body is going to continue to adapt to the lower level of carbohydrates in the diet in a couple of ways:
- Increased fat use
- Increased ketone production
- Improved insulin sensitivity
- More efficient use of glucose
How does the body adapt to use fat and probably more importantly, WHY does the body go through those adaptations?
What’s the advantage of increasing the use of fat and ketone bodies on a low-carb diet?
More importantly, why would the body become insulin resistant again when we’ve worked so hard to change and fix the previous insulin resistance when overweight?
The secret is adaptive glucose sparing.
What is Adaptive Glucose Sparing?
In response to a very low-carb, high fat diet, the muscles will increase mitochondrial density as they adapt to a smaller amount of glucose for energy. As a response to increasing blood ketone levels and lower blood glucose levels, the muscles will also increase local storage of triglycerides in the muscle. During exercise, the body will mobilize this locally stored triglycerides and break the triglycerides into fatty acids to be used by the muscle for energy in the mitochondria.
Peripheral insulin resistance
As the muscles become better adapted to a low-carb diet, the muscles will become somewhat insulin-resistant because they need less glucose because of their fat-adaptation. The body will prioritize the blood glucose for the brain and other organs that continue to use glucose as their primary fuel source.
Its important to realize the significant difference between the pathological insulin resistance seen in people on a high-carb/high-fat diet that leads to diabetes versus a normal physiological insulin resistance in muscles as a response to lower insulin and glucose levels.
A ketogenic diet (and intermittent fasting for that matter) can be an important tool for improving or reversing pathological insulin resistance. We see the benefit of intermittent fasting and a ketogenic diet as a treatment for polycystic ovarian syndrome (PCOS.)