I have heard some say that insulin resistance is helped by low carb diets. I have seen studies showing improved fasting blood glucose levels after eating lowcarb for even only a few weeks. I have also heard some say that eating lowcarb causes increased blood glucose response to sugar intake which is a sign of increased insulin resistance. One popular guru advocates increased carb consumption starting several days before a glucose challenge test in order to ameliorate this effect beforehand. So does lower carb eating cause insulin resistance or does it help cure insulin resistance? Which one is it-explanation please!
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While there's a lot to chew on for this topic, the good doctor Harris explains it well: "Peripheral (muscle) insulin resistance is a normal response to VLC as your muscles are running on fatty acids- otherwise you would get hypoglycemic. The confusion about IR is conflating glucose tolerance with pathologic insulin resistance. Insulin resistance per se is a physiologic adaptation. Insulin resistance in the liver on a high carb diet is pathologic. Many researchers seem to have no concept of the difference between peripheral and central (hepatic) insulin resistance."
There's a problem comparing different studies, of which there are dozens. The populations are very different--obese, normal bodyweight, diabetic, nondiabetic, women only, etc.
An interesting note is that high fat diets composed largely of PUFA improve insulin resistance much more than high fat diets composed largely of saturated fats. Moreover, ketogenic diets (eh, in rats) worsen glucose homeostasis compared to a high carb diet.
OK, so I think I get the gist now. Basically, if you eat very low carb, and so you don't have access to tons of glucose, so a lot of your cells switch to burning fatty acids instead of glucose and also these same cells which are now running on fatty acids become more resistant to taking up glucose in order to save it for use by those few cells that have to have glucose, like in the brain. Thus, it is a healthy saving mechanism. When glucose becomes more sparse, the cells that have the option of running on fatty acids, which is not sparse, choose to not use the glucose and instead use the fatty acids. Thus you can say those cells have become resistant to glucose, because they are saving it for other cells that really need it. But it is a healthy response designed to keep those few cells that need glucose having a good supply of it, and at the same time, it will maintain a healthy level of glucose in the blood. So this would be a type of insulin resistance that results in a healthy level of blood glucose.
The only problem comes if you eat very low carb for a while, and your cells adapt to this low level of glucose, and then suddenly you pound a ton of sugar into your system, and your cells are caught flat footed for a while. For a long time, they had adapted to a strategy of saving glucose and then all of the sudden, they are now awash in way too much glucose! Glucose glucose everywhere! But it will take them a bit longer to deal with all this sudden glucose because they were not adapted to it. Thus, it will take them longer to wake up and smell the coffee and realize they need to start sucking in the glucose again. End result is a higher blood glucose spike in response to a glucose challenge for those who have become very low carb adapted, than for those whose cells have not become so fatty acid using and glucose sparing. However, the good news is that after a few days of eating a bit more carbs, the fatty acid adapted cells can learn to be more flexible again and so their insulin resistance can easily be 'fixed.' Because they were never damaged, just adapted to one thing and then temporarily surprised by a sudden change.
Whereas in the case of pathologic insulin resistance brought on we think by long term high carb consumption, the problem is that something is damaged in the cells and cannot and will not adapt via more of the same. And the end result is too high fasting blood glucose instead of healthy levels of blood glucose. Big difference!
OK, so now the only thing I am left confused about is the mentioning on some of the links of vlc causing a higher FASTING blood glucose. I have not seen the studies on this. Any links on this one? All the studies I have seen have been on diabetics acquiring much lower and more healthy levels of fasting blood glucose via low carb. But all those studies were on diabetics, not on those starting in the healthy bg range. I have not (yet) seen any studies on anyone getting higher fasting blood glucose levels due to low carb. WOuld like to get some details on that one.
The rules are different for those of us who run on fat instead of on glucose. (Speaking loosely of course.) See Matthew's answer and then my follow-up answer on the old paleohacks thread: http://paleohacks.com/questions/4647/does-a-sugar-bolus-hit-you-like-the-flu/
The links to Peter are key. Though I'm guessing, Eva, that maybe you've already read them judging by what you said. Also I guess I'm more or less agreeing with Kamal via KGH here.