Relative Insulin Resistance
 

Hey folks,

I know there's a lot of talk of insulin resistance in low carb dieting circles, but shouldn't we be talking instead about the relative insulin resistance of adipose tissue vs muscle tissue?

If your adipose tissue is more insulin sensitive than your muscle tissues, wouldn't fuel partitioning dictate that you will get fat? Similarly if your muscle tissue is more insulin sensitive than your adipose tissue, shouldn't you get muscular and lean?

So it seems to me that relative insulin resistance may be something important to consider as well as overall insulin resistance. And then we would need to find a mechanism to explain this difference in relative insulin resistance.

Is there any merit to this idea? Tell me if I'm wrong.

Sort of, yeah. Just like other tissue, fat tends to be come more insulin resistant with exposure, especially as it reaches its potential for growth. People talk about getting fat because insulin resistance drives their insulin up and that drives up fat mass. You gotta throw in liver insulin resistance there as well, it's pretty important.

There's stuff showing not much fat growth after insulin resistance develops, other stuff where insulin resistance/high insulin comes first. Probably depends in part on how the insulin resistance develops. The most common suggested path is fat cells becoming overloaded, this leads to spillover fat in the liver etc. (this can also occur to muscle, especially in type II diabetes). Since in this case the insulin resistance is caused by fat cells being overloaded, they're a bit resistant to further fattening. Get insulin high enough, and they may respond, and all those other tissues being insulin resistant may get insulin high enough to promote further fattening. Some people get to 500 pounds and are still insulin sensitive, others to 200 (or 160 for that matter) and are already type II, the second are already exposed to higher insulin than the first, but will likely never be as heavy.

An example for insulin resistance preceding obesity is those mice fed fructose for six months, and then a "high fat diet" afterwards making them fatter. Fructose in rodents just replacing glucose in their usual chow is more of an insulin resistance model, the animals don't necessarily get fat unless some fat is included. Once they're insulin resistant, switching to a high fat diet is more fattening, they blame it on leptin resistance but other people are willing to blame the leptin resistance on the insulin resistance.