T Nation

Insulin

Can someone explain how insulin insensitivity causes fat gain?

If you’re insulin insensitive, your muscles are less responsive to insulin but doesn’t that make your fat cells less responsive as well? And if you’re insulin sensitive, which is regarded as a good thing, wouldn’t your fat cells be sensitive to insulin as well?

Also, do artificial sweeteners like aspartame have any effect on insulin at all?

The theory is that muscle cells become insulin resistant before fat cells, even though I have not seen any research on this. If anyone has seen this demonstated I would like to see a reference. If this is the case then glucose would not be taken up by the muscle and would be transported to the liver or adipocytes where it would be converted to fatty acids which would enlarge fat stores and increase tryglyceride levels. If one is insulin sensitive that keeps blood sugar down which will reduce insulin levels and lead to a better fat burning environment. Also, aspartame does not affect insulin release (Physiol Behav. 2002 Feb 1-15;75(1-2):41-7).

Thanks for the info Ken. I suppose once the muscles glycogen stores are full (I believe it’s like 600g for an average person), the excess glycogen gets stored in the fat cells regardless how insulin sensitive you are?