A DISTURBING study on Caffeine
(Taken from T-mag's John M. Berardi)
....
1) Caffeine intake (in all of its forms) decreases whole body glucose disposal (carbohydrate uptake) by 15-30%.
2) Caffeine intake decreases skeletal muscle glucose disposal by 50%.
3) When consumed with a standard carbohydrate breakfast, caffeine decreases insulin sensitivity, leading to large increases in blood insulin. But even in the face of this insulin surge, blood glucose doesn't disappear at a normal rate. When the body can't take up carbohydrates properly (as when drinking coffee), it releases loads of insulin to help out. However, the coffee actually prevents the insulin from doing this job and you end up with high insulin and glucose. That, my friends, is the serum profile of the obese, type II diabetic.
4) Caffeine decreases insulin sensitivity for at least three hours (this is the duration of the longest study they've performed), but the true duration of the effect isn't known. I speculate that it's at least five hours, the half life of caffeine...