I've read in several posts here that in ketosis, the muscles become insulin resistant to spare glucose for the brain. I've also read that prolonged ketogenic diets increase insulin resistance.
I've also read that such diets are good for resting the system of a person with chronic insulin resistance.
Currently, I'm reading "The Art and Science of Low Carbohydrate Living". It's a fantastic book. However, it says more than once that studies on low carb diets lowered insulin resistance.
Which is it?
Low-carbohydrate diets generally help reduce the harmful form of insulin resistance associated with type 2 diabetes, abdominal obesity and PCOS.
However, a very low carb intake can also induce a non-harmful and reversible form of insulin resistance to spare glucose for your brain. This type of insulin resistance is mild and is not associated with disease. It is reversible once you reintroduce a bit more carbs back into your diet. This is why an OGTT (oral glucose tolerance test) will NOT BE VALID if you are eating less than 50-100 grams of carbs a day. Most doctors are unfortunately not aware of it and may mistakenly diagnose you with diabetes or gestational diabetes (if you are pregnant). If you are going for such a test, make sure you reintroduce more carbs in your diet for about a week to get more accurate results.
I'm not althogether sure what difference it makes.
On a low-carb diet your Blood Glucose levels will generally be low anyway (because you're not spiking your blood with glucose and because your metabolism is using less glucose). So what difference does it make if your insulin response is impaired?
It's only really a problem if you suddenly switch from a low-carb to a high-carb diet, and even then the adjustment is pretty quick - about 24 hour if I recall correctly.
I'm a T2 diabetic on <20g of carb a day. My HbA1c is 4.5%. I couldn't really give a shit if it's temporarily increased my insulin resistance, because my BG never goes above 6mmol/l (108 mg/dl). I know for sure that I'm giving my pancreas a rest, and by losing weight I'm decreasing my overall insulin resistance.
You need to look at the bigger picture, I think.
Aglaee is correct. It is all about context and the difference between physiological insulin resistance (a natural adaptation to a low carb diet) and pathological insulin resistance (harmful type II diabetes).
Matt Lalonde goes into great detail into the difference between the two here (discussion starts at the bottom of page 14): https://robbwolf.com/wp/wp-content/uploads/2011/02/The-Paleo-Solution-Episode-68.pdf
When you are taking in very low carbohydrate and there is little glucose to spare, the body attempts to limit glucose consumption by muscles and reserves it for by the brain. This is a normal physiological survival response and not "insulin resistance" in the classical sense.
Mark Sisson wrote a good article describing this:
As I understand it, this is less "insulin resistance" than the body deliberately going into a mode where it will not release insulin so as to prevent the brain being deprived of glucose by your muscles. If you increase your carbohydrate intake your body will resume proper insulin response when there is sufficient glucose to go around.
If you are working on losing fat (desirable to reverse true insulin resistance) and are in low carbohydrate Paleo, you may run into the above situation. It would look like poor blood sugar control if you had your fasting blood sugar tested, but you would also probably have low insulin levels (something that is rarely checked) that would indicate this as a glucose-sparing response, not insulin resistance.
Besides general weight gain, insulin resistance is associated with abdominal obesity, high blood pressure, high triglycerides, and low HDL ("good cholesterol"). These conditions are part of a constellation of problems called metabolic syndrome (also called insulin resistance syndrome). Because this group of symptoms occurs together, it's hard to know what causes what, but metabolic syndrome is a risk factor for heart disease and Type 2 diabetes.